Midmark UltraComfort, UltraTrim Service manual

Dental

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Style B

Chair

Service and

Midmark UltraComfort

®

& UltraTrim® Dental Chair

Serial Number Prefixes:
NT, NZ & V

(UltraComfort shown)

Parts Manual

Dental
Chair

FOR USE BY MIDMARK
TRAINED TECHNICIANS ONLY

SF-1620 Part No. 004-0287-00 (7/14/15)

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TABLE OF CONTENTS

TABLE OF CONTENTS

Section/Paragraph................................................Page Section/Paragraph ............................................... Page

IMPORTANT INSTRUCTIONS

General Safety Instructions ..........................................iii

Safety Alert Symbols ....................................................iii

Warranty Instructions ................................................. iii

SECTION I GENERAL INFORMATION

1.1 Scope of Manual .......................................... 1-1

1.2 How to Use Manual ...................................... 1-1

1.3 Description Of Midmark Dental Chair........... 1-1

1.4 Standard Torque Specifications.................... 1-7

1.5 Specifications ............................................... 1-7

1.6 Parts Replacement Ordering........................ 1-9

1.7 Special Tools ................................................ 1-9

SECTION II TESTING AND TROUBLESHOOTING

2.1 Operational Test .......................................... 2-1

2.2 Testing Positioning Potentiometer ................ 2-4

2.3 Troubleshooting Procedures......................... 2-6

SECTION III SCHEDULED MAINTENANCE

3.1 Scheduled Maintenance ............................. 3-1

SECTION IV MAINTENANCE/SERVICE
INSTRUCTIONS

4.1 Introduction................................................... 4-1

4.2 Upholstery

Removal .................................................... 4-1

Installation ................................................. 4-1

4.3 Covers

Removal .................................................... 4-2

Installation ................................................. 4-2

4.4 Headrest

Adjustment ................................................ 4-3

4.5 Rotational Brake

Removal .................................................... 4-4

Installation ................................................. 4-4

4.6 Membrane Touchpad

Removal .................................................... 4-5

Installation ................................................. 4-5

4.7 Hydraulic Back Cylinder

Removal .................................................... 4-5

Installation ................................................. 4-6

4.8 Hydraulic Base Cylinder

Removal .................................................... 4-7

Installation ................................................. 4-9

4.9 Hydraulic Pump

Removal .................................................. 4-10

Installation ............................................... 4-12

4.10 Capacitor, Motor Pump

Removal .................................................. 4-12

Installation ............................................... 4-13

4.11 Hydraulic Reservoir

Removal.................................................. 4-13

Installation............................................... 4-14

4.12 Hydraulic Fluid Level

Checking / Adding................................... 4-14

4.13 Hydraulic Solenoid Valve Assembly

Removal.................................................. 4-15

Installation............................................... 4-18

Adjustments ............................................ 4-18

4.14 Printed Circuit (P.C.) Board

Removal.................................................. 4-19

Installation............................................... 4-19

4.15 Fuses (P.C. Board)

Replacement .......................................... 4-19

4.16 Base Potentiometer

Removal.................................................. 4-20

Installation............................................... 4-21

Adjustment.............................................. 4-21

4.17 Back Potentiometer

(SN NZ1000 - NZ1019)

(SN NT1000 - NT1598)

Removal.................................................. 4-22

Installation............................................... 4-23

Adjustment.............................................. 4-24

4.18 Back Potentiometer

(SN NZ1019 to Present)

(SN NT1599 to Present)

Removal.................................................. 4-25

Installation / Adjustment.......................... 4-26

4.19 Safety Bail Limit Switch

Removal.................................................. 4-26

Installation............................................... 4-26

4.20 Hydroglide Assembly

Removal.................................................. 4-27

Installation............................................... 4-28

4.21 Foot Switch Control

Removal.................................................. 4-28

Installation............................................... 4-28

4.22 Using Manual Override Function

Operation ................................................... 4-30

SECTION V SCHEMATICS / DIAGRAMS

5.1 Electrical / Hydraulic Diagrams
P.C. Board / Related Circuitry (115 VAC). 5-1
P.C. Board / Related Circuitry (230 VAC).. 5-4

SW1 Switch Settings ................................ 5-7

J1 thru J5 Pendants .................................. 5-8

J-Box Wiring Diagram ............................... 5-9

Console / Accessory Wiring Diagram ..... 5-10

Base Up Hydraulic Function ................... 5-11

Base Down Hydraulic Function............... 5-12

Back Up Hydraulic Function.................... 5-13

Back Down Hydraulic Function ............... 5-14

(*) Indicates that there has been a serial number break for the illustration

and that there are additional point page(s) following the original page.

© Midmark Corporation 2000 SF-1620 Page i Printed in U.S.A.

Rev. 10/12

TABLE OF CONTENTS

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SECTION VI PARTS LIST

6.1 Introduction ................................................. 6-1

6.2 Description Of Columns ............................... 6-1

6.3 Torque Specifications And Important

Assembly Notes ........................................... 6-1

Pictorial Index (UltraComfort ®) .................. 6-2

Pictorial Index (UltraTrim) ............................ 6-3

Silhouette Upholstery (UltraComfort ®) ...... 6-4

Ultraleather Upholstery (UltraComfort ®).... 6-5

Silhouette Upholstery (UltraTrim)................. 6-6

Ultraleather Upholstery (UltraTri m) .............. 6-7

Double Articulating Headrest ......................6-8*

Magnetic Headrest ....................................... 6-9

Covers .......................................................6-10*

Base Components ..................................... 6-11

Seat Components ..................................... 6-12*

Brake Components .................................... 6-13

Back Components (UltraComfort ®) ......... 6-14

Back Components (UltraTrim) ................... 6-15

Hydraulic Components.............................. 6-16*

Hoses and Fittings ..................................... 6-17

Electrical Components..............................6-18*

Foot Control ............................................... 6-19

L/R and Console Components.................. 6-20*

Remote Mounted Chair Control ................ 6-21*

COMMENTS ............................................................. 7-1

FAX ORDER FORM.................................................. 7-2

(*) Indicates that there has been a serial number break for the illustration

and that there are additional point page(s) following the original page.

© Midmark Corporation 2000 SF-1620 Page ii Printed in U.S.A.

Rev. 10/12

TABLE OF CONTENTS

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General Safety Instructions

Safety First: The primary concern of Midmark Cor­poration is that this chair is maintained with the safety

of the patient and staff in mind. To assure that services
and repairs are completed safely and correctly, proceed
as follows:

(1) Read this entire manual before performing any

services or repairs on this chair.

(2) Be sure you understand instructions contained

in this manual before attempting to service or
repair chair.

Safety Alert Symbols

Throughout this manual are safety alert symbols that
call attention to particular procedures. These items are

used as follows:

DANGER

A DANGER is used for an imminently

hazardous operating procedure, prac­tice, or condition which, if not correctly followed,
will result in loss of life or serious personal
injury.

NOTE

A NOTE is used to amplify an operating procedure,
practice or condition.

Warranty Instructions

Refer to Midmark “Limited Warranty” printed in the
Installation and Operation Manual for warranty informa­tion. Failure to follow guidelines listed below will void
the warranty and/or render the Dental Chair unsafe for
operation.

• In event of a malfunction, do not attempt to use
dental chair until necessary repairs have been
made.

• Do not attempt to disassemble chair, replace mal­functioning or damaged components, or perform
adjustments unless you are one of Midmark’s
authorized service technicians.

• Do not substitute parts of another manufacturer
when replacing inoperative or damaged compo­nents. Use only Midmark replacement parts.

WARNING

A WARNING is used for a potentially

hazardous operating procedure, prac­tice, or condition which, if not correctly followed,
could result in loss of life or serious personal
injury.

CAUTION

A CAUTION is used for a potentially haz-

ardous operating procedure, practice, or
condition which, if not correctly followed, could result
in minor or moderate injury. It may also be used to
alert against unsafe practices.

EQUIPMENT ALERT

An EQUIPMENT ALERT is used for an

imminently or potentially hazardous oper­ating procedure, practice, or condition which, if not
correctly followed, will or could result in serious, mod­erate, or minor damage to unit.

© Midmark Corporation 2000 SF-1620 Page iii Printed in U.S.A.

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SECTION I

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GENERAL INFORMATION

SECTION I

GENERAL INFORMATION

1.1 Scope of Manual

This manual contains detailed troubleshooting, sched­uled maintenance, maintenance, and service instruc­tions for the Midmark Dental Chair. This manual is
intended to be used by Midmark’s authorized service
technicians.

1.2 How to Use Manual

A. Manual Use When Performing Scheduled Mainte-

nance.

(1) Perform inspections and services listed in

Scheduled Maintenance Chart (Refer to
para 3.1).

(2) If a component is discovered to be faulty or out

of adjustment, replace or adjust component in
accordance with maintenance / service instruc­tions (Refer to para 4.1).

B. Manual Use When Unit Is Malfunctioning And

Cause Is Unknown.

(1) Perform an operational test on chair (Refer to

para 2.1).

(2) Perform troubleshooting procedures listed in

Troubleshooting Guide (Refer to para 2.2).

(3) If a component is discovered to be faulty or out

of adjustment, replace or adjust component in
accordance with maintenance / service instruc­tions (Refer to para 4.1).

C. Manual Use When Damaged Component Is Known.

(1) Replace or adjust component in accordance

with maintenance / service instructions (Refer
to para 4.1).

1.3 Description Of Midmark Dental Chair

A. General Description (See Figure 1-1).

The Midmark Chair is a dental operating chair designed
for the general dentistry market. The chair is hydrauli­cally positioned using a hydraulic pump, back, base cyl­inders and solenoid valve unit that are activated by
depressing either the desired membrane or foot switch.

B. Major Serviceable Components (See Figure 1-1).

Hydraulic Motor Pump (1, Figure 1-1)

Motor Pump provides hydraulic pressure to system and
works with the solenoid valves, check valves, and throt­tle valves to operate Back and Base cylinders.
A capacitor, mounted near the reservoir, provides start
and run power.
Motor is for intermittent
will cause motor to overheat, causing internal thermal
overload to open, removing power from motor. Normal
cool off period for thermal overload to reset is approxi­mately 10 minutes.

Solenoid Valve Unit (2, Figure 1-1)

Solenoid Valve Unit consist of Back Up, Back Down,
Base Up, and Base Down Solenoid valves.
Four manually set Throttle Valves (TV1, TV2, TV3, and
TV4) control flow of hydraulic fluid during various func­tions.
Two Check Valves (CV1 and CV2) prevent fluid from
back flowing through Base Up and Back Up Solenoid
Val ves.
A Pressure Relief Valve protects the system should
higher then normal pressure occur during operation.

Back Hydraulic Cylinder (3, Figure 1-1)

Back Hydraulic Cylinder is a single-acting cylinder. Dur­ing Back Up operation the Motor Pump is operating to
create hydraulic pressure required to raise the cylinder.
During Back Down function Motor is not
cylinder operates by pressure created by equipment
and patient weight to lower Back section.

Base Hydraulic Cylinder (4, Figure 1-1)

Base Hydraulic Cylinder is a single-acting cylinder. Dur­ing Base Up operation the Motor Pump is operating to
create hydraulic pressure required to raise the cylinder.
During Base Down function Motor is not
cylinder operates by pressure due to equipment and
patient weight to lower Base section.

operation. Continuous operation

running and the

running and

© Midmark Corporation 2000 SF-1620 Page 1-1 Printed in U.S.A.

SECTION I

Figure 1-1. Component Location

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GENERAL INFORMATION

© Midmark Corporation 2000 SF-1620 Page 1-2 Printed in U.S.A.

SECTION I

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GENERAL INFORMATION

P.C. Board w/ Fuses (5, Figure 1-1)

Printed Circuit Board contains 115 VAC or 230 VAC line
voltage, 12 VDC, and 5 VDC plug connectors, 12 VDC
supply transformer for control circuitry, Pump, Base and
Back control relays, two 6.5 amp (115 VAC) or 3.15 amp
(230 VAC) line input fuses, one 100 mA fuse for 115
VAC Input to P.C. Board Transformer,
RV1 Surge Protector for over-voltage spikes, Program
switch (SW1), Calibration Button (SW2), and main
Microprocessor (U6).

Back and Base Positioning
Potentiometers (6, Figure 1-1)

Positioning Potentiometers provide P.C. board with
information, thru voltage change, on the positions of
Base and Back sections during operation.
P.C. board, during calibration mode, uses the potenti­ometers to determine where end of travel points are for
Base and Back. It stores this information and, while
monitoring voltage output of potentiometers, prevents
chair from reaching extreme ends of travel.
Output voltage from potentiometers allows P.C. board,
thru use of program and positioning buttons, to store
desired chair positions in P.C. board memory.
After a position has been programmed, depressing that
programmed button (1 thru 4) will automatically move
the chair to the position.

Safety Bail Limit Switches (7, Figure 1-1)

Two Safety Bail Limit Switches are normally closed
(N.C.) switches located on patient’s
parallel arms.
During chair’s descent, if bottom lift arm cover contacts
an obstruction, cover will depress switch actuator(s) of
Safety Bail Limit Switch(es). The normally closed con­tacts open, removing power from Base Down and Back
Down solenoid coils at plug connectors J17 (4 & 5) and
J18 (4 & 5) on PC board. Base Up and Back Up will
continue to work.
When the obstruction is removed, the switch(es) return
to the N.C. position. To continue a function, depressing
that function button allows chair to continue its opera­tion.

right and left side

Membrane Touch Pads (8, Figure 1-1)

Membrane touch pads are located on both sides of the
chair or on consoles of the delivery systems. Operate
the chair by depressing one of four directional arrow
buttons that corresponds to back or seat graphic.
Depressing one of the four program buttons (1 thru 4)
allows for chair movement to a predetermined setting.
The functions can be stopped by momentarily depress­ing any switch on the touch pads or foot control.
A hidden switch, located in the center of the directional
arrows on the pad, is for setting programmed positions.

Foot Switch (9, Figure 1-1)

Foot Switch consist of four directional arrow buttons,
four numbered program position buttons and a button,
designated by the letter “P”, for programming.
Depressing one of the four directional arrow buttons
that corresponds to the back or seat graphic moves
chair in that direction.
Depressing one of the four program buttons (1 thru 4)
allows for chair movement to a predetermined setting.
Functions can be stopped by momentarily depressing
any switch on the touch pads or foot control.
The button, with the letter “P”, is for setting programmed
positions.

Rotational Seat Lock (10, Figure 1-1)

The chair seat will rotate 30° each way from center-line
for a stand-alone and console chair. For a L / R chair it
will rotate 15°. To release the rotational lock, rotate the
handle toward the patient’s right side.
To engage the rotational lock, rotate the handle toward
the patient’s left side.

Headrest Locking Assembly (11, Figure 1-1)

Headrest height can be changed by pulling out or push­ing in on headrest. Tension of headrest locking assem­bly is pre-set at factory but can be adjusted if required.

© Midmark Corporation 2000 SF-1620 Page 1-3 Printed in U.S.A.

SECTION I

RH Touch Pad Shown.

Figure 1-2. Membrane Touch Pads.

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GENERAL INFORMATION

C. Theory of Operation (Refer to Figure 1-4 and

Section V for wiring diagram, electrical sche­matics and hydraulic layouts).

Electrical Power:

Line voltage is supplied to chair’s Main PC Board thru
power cord.
F1, F2, and F3 replaceable fuses, protect P.C. Board
from excessive current draw.
RV1 Surge Suppressor, protects P.C. board from volt­age spikes by partially blocking electrical flow until sup­ply voltage returns to a normal value.
A transformer along with voltage regulators on PC cir­cuit board reduces line voltage to 12 and 5 VDC. This
provides power to operate the circuitry on PC circuit
board, limit switches, membrane switch panel, and foot
control.
Relays K1 thru K5 on P.C. board are for line voltage
operation of Solenoid Valves and Motor Pump.
LED’s, next to the specific relay, lights when that relay is
operated.

Operation of Membrane Switch Panels (Figure 1-2):

PC circuit board supplies 5 VDC to one side of each
normally open (N.O.) switches in membrane switch
panel. Pressing a membrane switch, closes contacts,

completing a circuit, allowing a signal to return to PC
circuit board, activating the function selected.
Functions available are Back Up and Down, Base Up
and Down, Programmed settings, 1 thru 4, and a Pro­gramming button “P”.

Program Function (Figure 1-2):

Using the Directional buttons, place chair in a desired
position. Press Program (P) button, unmarked button in
middle of Directional buttons. There is a short audible
beep after which you have three (3) seconds to depress
the desired Program Position button (1,2, 3, or 4). When
the Position button is depressed, three audible beeps
are sounded indicating the position has been stored.
Pressing the Position button will bring the chair to the
position that was programmed.

Manual Override Function (Figure 1-2):

Pressing and holding the Program (P) button while
pressing a Directional button by-passes the feedback
coming from the back and base potentiometers. This
allows for operation of the chair should a potentiometer
malfunction. This should only be used should a patient
be on the chair to allow for safe exit. Service should be
called to repair malfunction.

Operation of Foot Control (Figure 1-3):

PC circuit board supplies 5 VDC to one side of each of

© Midmark Corporation 2000 SF-1620 Page 1-4 Printed in U.S.A.

SECTION I

Figure 1-3. Foot Control

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GENERAL INFORMATION

the normally open (N.O.) switches in foot switch. Press­ing one of the switches, closes the contacts, completing
a circuit, allowing a signal to return to PC circuit board,
activating the function selected.
Functions available are Back Up and Down, Base Up
and Down, Programmed settings 1 thru 4, and a Pro­gramming button “P”. Should a malfunction occur the
Manual Override function can be used.
Program Function (Figure 1-3):
Using the Directional buttons, place chair in a desired
position. Press Program (P) button. There is a short
audible beep after which you have three (3) seconds to
depress the desired Program Position button (1,2, 3, or

4). When a Position button is depressed, three audible
beeps are sounded indicating the position has been
stored.
Pressing the Position button will bring the chair to the
position that was programmed.

Manual Override Function (Figure 1-3):

Pressing and holding the Program (P) button while
pressing a Directional button by-passes the feedback
coming from the back and base potentiometers. This
allows for operation of the chair should a potentiometer
malfunction. This should only be used should a patient
be on the chair to allow for safe exit. Service should be
called to repair malfunction.

Back Up Function Operation (Figure 1-4):

Depressing and holding one of the Back Up directional
button completes a circuit to the PC board.
On the PC board, K4 contacts close supplying line volt­age to connector J18, pins 2 and 3, to the Back Up sole­noid coil, energizing the coil, opening the hydraulic
valve.
At the same time, K1 contacts close supplying line volt­age to connector J16, pins 2 and 3, to the hydraulic
motor pump, energizing the pump.
During the Back Up function, the Back Potentiometer,
connected to J9 connector, signals movement of the
Back section.
During normal operation, when the potentiometer
reaches the calibrated position, just before the extreme
end of travel, the signal it sends back to the PC board
tells the board to open K1 and K4 contacts removing
power from the Back Up solenoid valve and hydraulic
pump motor.

Back Down Function Operation (Figure 1-4):

Depressing and holding one of the Back Down direc­tional button completes a circuit to the PC board.
On the PC board, K5 contacts close supplying line volt­age to connector J18, pins 4 and 5, to the Back Up sole­noid coil, energizing the coil, opening the hydraulic
valve.

© Midmark Corporation 2000 SF-1620 Page 1-5 Printed in U.S.A.

SECTION I

LED

LED

LED

LED

LED

LS1

SW1
(Prog.)

Main P.C.
Board

SW2
(Calib.)

U6

ON

OFF

Dental Chair
115 VAC

NC

C

NC

C

Limit Switch Layout

C

NO

NC

1122443

3

NO

C

For Pendant (J1 thru J6)
Connectors Refer to
Pendant P.C. Schematics

NOTE:
For Harness Part Numbers
Refer to Section 5.

(Remove when

installing cuspidor)

Figure 1-4. Main P.C. Board and Related Components

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GENERAL INFORMATION

During the Back Down function, the Back Potentiome­ter, connected to J9 connector, signals movement of the
Back section. During normal operation, when the poten­tiometer reaches the calibrated position, just before the

extreme end of travel, the signal it sends back to the PC
board tells the board to open K5 contacts and remove
power to the Back Down solenoid valve.

© Midmark Corporation 2000 SF-1620 Page 1-6 Printed in U.S.A.

Rev. 1/14

SECTION I

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GENERAL INFORMATION

Base Up Function Operation (Figure 1-4):

Depressing and holding one of the Base Up directional
button completes a circuit to the PC board.
On the PC board, K2 contacts close supplying line volt­age to connector J17, pins 2 and 3, to the Base Up
solenoid coil, energizing the coil, opening the hydraulic
valve.
At the same time, K1 contacts close supplying line volt­age to connector J16, pins 2 and 3, to the hydraulic
motor pump, energizing the pump.
During the Base Up function, the Base Potentiometer,
connected to J8 connector, signals movement of the
Base section. During normal operation, when the poten­tiometer reaches the calibrated position, just before the
extreme end of travel, the signal it sends back to the PC
board tells the board to open K1 and K2 removing
power to Base Up solenoid valve and hydraulic pump
motor.

Base Down Function Operation (Figure 1-4):

Depressing and holding one of the Base Down direc­tional button completes a circuit to the PC board.
On the PC board, K3 contacts close supplying line volt­age to connector J17, pins 4 and 5, to the Base Down
solenoid coil, energizing the coil, opening the valve.
During the Base Down function, the Base Potentiome­ter, connected to J8 connector, signals movement of the
Base section. During normal operation, when the poten­tiometer reaches the calibrated position, just before the
extreme end of travel, the signal it sends back to the PC
board tells the board to open K3 contacts and remove
power to the Base Down solenoid valve.

Safety Bail Limit Switches (Figure 1-4):

During Base or Back Down operations, as chair is
descending, should bottom lift arm cover contact an
obstruction, one or both normally closed (N.C.) Safety
Bail Limit Switches, located beneath cover, will open.
Power is removed from Base and Back solenoid valves,
closing the valves, stopping descent of both base and
back. Base Up and Back Up functions will continue to
work.
Removing the obstacle, returns switch contacts to
closed position.
Press the desired directional or program button to
resume operation.

1.4 Standard Torque Specifications

The following standard torque specifications in
Table 1-1 apply to the hardware used on the unit unless
otherwise listed elsewhere in the service procedures or
parts illustrations.

Table 1-1. Torque Specifications

Hardware Size* Torque Values

#6 .............................. 11 to 21 inch-lbs. (1.2 to 2.3 N•M)

#8 .............................. 20 to 30 inch-lbs. (2.2 to 3.3 N•M)

#10 ............................ 32 to 42 inch-lbs. (3.6 to 4.8 N•M)

1/4 inch ..................... 75 to 85 inch-lbs. (8.5 to 9.6 N•M)

5/16 inch ...................18 to 22 ft.-lbs. (24.4 to 29.8 N•M)

3/8 inch .....................31 to 35 ft.-lbs. (42.0 to 47.5 N•M)

1/2 inch .....................50 to 60 ft.-lbs. (67.8 to 81.4 N•M)

* All hardware should be grade 5 or above.

1.5 Specifications

Factual data for the Midmark Dental Chair is provided in
Table 1-2. Also, see Figure 1-5.

Table 1-2. Specifications

Description Data

Maximum Patient Weight.......................300 lbs (136 kg)

Weight of a Unit:
Without Shipping Carton

Chair Only ......................................290 lbs (132 kg)

Chair (L / R or Console) 310 lbs (141 kg)
With Shipping Carton

Chair Only ......................................350 lbs (159 kg)

Chair (L / R or Console)l.................370 lbs (168 kg)

Hydraulic Fluid Requirements

System Capacity ........................... 1 Quart (950 ml)

Type of Hydraulic Fluid ........................... ISO VG 32

Electrical Requirements:..................... 115 VAC +/-10%,

5A, 60 HZ,

single phase

or

230 VAC +/-10%,

2.5A, 50/60 HZ,
single phase

Fuse Rating*:

F1 Line Fuse, 115 VAC ................. T6.3 AL, 250 VAC

5 x 20mm, Type Slo-Blo

or

© Midmark Corporation 2000 SF-1620 Page 1-7 Printed in U.S.A.

Rev. 10/12

SECTION I

29" max.

(73.7 cm)

27.5" max.
(69.9 cm)

58" max.

(147.3 cm)

22"

(55.9 cm)

25.8"

(65.6 cm)

11.2"

(28.4 cm)

20.7"

(52.5 cm)

25.9"

(65.8 cm)

10.3"

(26.1 cm)

20.5"

(52.7 cm)

8"

(20.3 cm)

20"

(50.8 cm)

8.75"

(22.2 cm)

27"

(68.6 cm)

27 .5"

(69.8 cm)

23"

(58.4 cm)

15o LR and Console

30

o

Chair Only

33" max. (83.8 cm)

w/ Back Level
30" max. (76.0 cm)
w/ Back Full Down

36"

(91.4 cm)

16.0" min.
(40.6 cm)

67"

(170.2 cm)

75"

(190.5 cm)

87"

(221.0 cm)

19.0" min. (48.2 cm)
w/ Back Level

16.25" min. (41.3 cm)
w/ Back Full Down

15"

(38.1 cm)

16.5"

(41.9 cm)

Ultra-Trim

Back

Ultra-Comfort

Back

Figure 1-5. Specifications

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GENERAL INFORMATION

F1 Line Fuse, 230 VAC.................T3.15 AL, 250 VAC

5 x 20mm, Type Slo-Blo

F2 Line Fuse, 115 VAC ..................T6.3 AL, 250 VAC

5 x 20mm, Type Slo- Blo

or

F2 Line Fuse, 230 VAC.................T3.15 AL, 250 VAC

5 x 20mm, Type Slo-Blo

F3 Transformer Fuse
115 VAC / 230 VAC ... T0.10 AL / T0.05 AL, 250 VAC

5 x 20mm, Type Slo-Blo

(*Fuses are located on P.C. Board.)

Duty Cycle ................................... Intermittent Operation

(30 seconds on / 5 minutes off,

motor run time)

WARNING

Should it be necessary to transport the

chair, its position is critical to ensure
safety. Before attempting to move / transport
chair, it must be lowered to its minimum height
and locked in place at 0° rotation (install shipping
bolt - refer to step 7 on page A-1 of the Installa­tion Guide, Module A). NOTE: Midmark strongly

recommends disassembling any accessory arms
(unit, light, etc.) from chair before attempting to
move / transport an entire operatory.

© Midmark Corporation 2000 SF-1620 Page 1-8 Printed in U.S.A.

Rev. 11/8/12

SECTION I

Figure 1-6. Model Number / Serial Number Location

Model / Serial

Number

Go To Table Of Contents

GENERAL INFORMATION

1.6 Parts Replacement Ordering

If replacement part(s) are required, order part(s) directly
from factory as follows:

(1) Refer to Figure 1-6 to determine location

of model number and serial number of chair
and record this data.
Refer to Parts List to determine item numbers
of parts, part numbers, descriptions, and quan­tities needed and record this data (Refer to
para 6.1).

NOTE

To assure expedient service and correct parts you
must have correct Model and Serial Number

of chair.

(2) Determine installation date of chair and record

this data. Call Midmark (1-800 643-6275) and
ask for Technical Service Department. Please
have Model and Serial Number

of chair.

Table 1-3. Special Tool List

Description of Special Tool

Multimeter * Commercially Available Any Type Used to perform continuity and voltage checks.

Scissor Jack (capable of lifting a
minimum of 1000 lbs. [454 kg])

Jack Stands (Qty. 2) (capable of
supporting 1000 lbs. [454 kg])

Jumper wire with insulated clips Made up by technician N/A For jumpering various test points during trouble-

Torque Wrench * Commercially Available Any Type Used to tighten nuts or screws to specified values.

Manufacturer’s

Name / Address / Phone

Commercially Available Any Type Used to elevate Back section when hydraulic Base

Commercially Available Any Type Used to support chair top when hydraulic base cyl-

* Tool should be calibrated annually to ensure proper specifications are met.

Manufacturer’s

Part Number

Purpose of Special Tool

cylinder or motor pump is malfunctioning.

inder or motor pump is being worked on.

shooting.

© Midmark Corporation 2000 SF-1620 Page 1-9 Printed in U.S.A.

Rev. 4/01

SECTION I

Go To Table Of Contents

GENERAL INFORMATION

© Midmark Corporation 2000 SF-1620 Page 1-10 Printed in U.S.A.

BACK

DOWN

PROGRAM

BUTTON

SEAT

UP

SEAT

DOWN

BACK

UP

RH Touch Pad Shown.

Figure 2-1. Operational Test

SECTION II

Go To Table Of Contents

TESTING AND TROUBLESHOOTING

2.1 Operational Test

In order to effectively diagnose a malfunction of chair, it
may be necessary to perform an operational test as fol-

lows:

WARNING

Refer to the Operator’s Manual for com-

plete instructions on operating the
chair. Failure to do so could result in personal
injury.

NOTE

The Operational Test, for the most part, only
describes what should happen when chair is oper­ated. If the chair does something other than
described, a problem has been discovered. Refer to
Troubleshooting Guide to determine cause of prob­lem and its correction.

SECTION II

TESTING AND TROUBLESHOOTING

WARNING

When performing various checks with

chair plugged in and covers off use
extreme care to prevent accidental electrical
shock. Failure to comply could cause severe
injury.

(1) Plug chair power cord into a grounded, non-iso-

lated, correctly polarized outlet, that has proper
voltage for chair.

(2) Depress Back Up, Back Down, Base Up, and

Base Down buttons on membrane switch panel
(Refer to Figure 2-1).

Observe. Chair should move in direction corre­sponding to button being depressed. Hydraulic
motor pump and cylinders should run quietly.
Movement should be smooth and match speed
and range of motions listed below:

Chair Speeds (±1 second w/ 180 lbs [82 kg]
load on chair)

Back Up to Back Down...................15 seconds

Back Down to Back Up...................15 seconds

Base Up to Base Down ..................15 seconds

Base Down to Base Up ..................15 seconds

See Figure 1-5 for max. and min. heights.

(3) Place a 300 lbs (136 kgs) weight on center of

seat section of chair.

Observe. Seat section should not drift down­ward under weight.

(4) Depress Base Up and Base Down buttons on

membrane switch panel.

Observe. Chair base should lift weight steadily
and without excessive noise.

(5) Remove weights from chair. Then, place a 100

lbs (45.4 kgs) weight on center of back section
of chair (with back section at approximately 45º
above horizontal).

© Midmark Corporation 2000 SF-1620 Page 2-1 Printed in U.S.A.

Rev. 8/01

SECTION II

Figure 2-2. Headrest

Figure 2-3. Rotational Lock

Go To Table Of Contents

TESTING AND TROUBLESHOOTING

(6) Depress Back Up and Back Down buttons on

membrane switch panel.

Observe. Back should lift weight steadily and
without excessive noise.

(7) Remove weights from chair.

(8) Run Back Up function all the way up and Base

Down function all the way down.

(9) Slide headrest in and out stopping at different

positions. Push gently against headrest at
each position (Refer to Figure 2-2).

Observe. Headrest should not require exces­sive force to position. When in a position, head­rest should not move when a slight pressure is
applied.

(10) If chair has Articulating Headrest, loosen knob,

move headrest to different positions.

Observe. Headrest should move smoothly
without requiring excessive force.

(11) Tighten knob.

Observe. Headrest should remain in position
when force is applied.

Observe. Chair top should rotate smoothly
and easily; not requiring excessive force. The
chair top should be able to be rotated from stop
to stop which is 60°

or 30° in each direction
from centerline of chair. L / R and console
chairs will rotate 30° and 15°.

(13) Tighten Rotation Lock lever to locked position.

Attempt to rotate chair top.

Observe. Chair top should not be able to be
rotated when Rotation Lock lever is engaged.

(14) Depress Back Up, Back Down, Base Up, Base

Down buttons on foot control (Refer to
Figure 2-4).

Observe. When each of the buttons on foot
control are depressed, appropriate function
should activate.

(12) Loosen Rotation Lock lever and rotate chair top

until it hits a stop. Then rotate chair top in
opposite direction until it hits a stop. (Refer to
Fig. 2-3).

© Midmark Corporation 2000 SF-1620 Page 2-2 Printed in U.S.A.

Rev. 10/12

(15) Depress Base Down membrane or foot switch.

Figure 2-4. Foot Control

Figure 2-5. Safety Bail Limit Switches.

PROGRAM
BUTTON

BACK

DOWN

SEAT

UP

BACK

UP

SEAT

DOWN

RH Touch Pad Shown.

Figure 2-6. Manual Override

Go To Table Of Contents

As chair descends, push upward on bottom lift
arm cover until one or both of the Safety Bail
Limit switches operate (Refer to Figure 2-5).

SECTION II

TESTING AND TROUBLESHOOTING

(16) Check Manual Override using touchpad mem-

brane switch or foot control. Depress and hold
Program (P) button and then depress desired
Manual positioning button(s) (Refer to
Figure 2-6 ).

NOTE

The Program button on Membrane Touchpads is
located directly above Seat graphic. On Foot Control
it is located on left side and designated with the letter
“P”.

Observe. Chair should move to desired posi­tion as long as buttons are being depressed.

CAUTION

This procedure should be used by the

operator only in case of a chair malfunction
should a patient be on chair. This permits positioning
the chair to allow a patient to safely exit chair.

Observe. When bottom lift arm cover contacts
and operates Safety Bail Limit switch(es) chair
should immediately stop its descent.

Releasing bottom lift arm cover, returns Safety
Bail Limit switch(es) to normally closed position.
Operating Base Down membrane or foot switch
will cause chair to descend again.

© Midmark Corporation 2000 SF-1620 Page 2-3 Printed in U.S.A.

Rev. 8/01

SECTION II

PROGRAM

POSITION

RECALL

BUTTONS

(EXAMPLE)

CURRENT CHAIR

POSITION

TO GO TO FAVORITE

PROGRAMMED POSI-

TION #1, DEPRESS

BUTTON “1”

Figure 2-7. Programmed Positions

Figure 2-8. Testing Potentiometer.

Go To Table Of Contents

TESTING AND TROUBLESHOOTING

(17) Check Programmed Positions using touchpads

or foot control. Depress one of the Programmed
recall buttons. The chair should advance to the
position programmed by the user (Refer to
Figure 2-7).

NOTE

Do not attempt to change a programmed position
unless requested by personnel at the Dental office.

(18) Press a Programmed Position again, while

chair is moving to position, press any button on
touchpad or foot control. Chair should stop all
movement.

2.2 Testing Positioning Potentionmeter

A. Check Continuity (Ohms)

WARNING

Unplug chair power cord before remov-

ing covers or working on chair. Failure
to comply could result in personal injury.

(1) Disconnect power to chair and remove uphol-

stery or covers whichever is applicable to
access potentiometer (refer to para 4.16
or 4.17).

(2) Set VOM on resistance (ohms) for a scale that

can read up to 6K ohms.

(3) After removing plug connector, place meter

probes (1, Fig. 2-8) on outside leads (A) of
potentiometer (2) for total resistance. Reading
should be 4K to 6K (ohms). Any reading out­side this or if no continuity reading is present,
replace potentiometer.

© Midmark Corporation 2000 SF-1620 Page 2-4 Printed in U.S.A.

(4) Move one meter probe to middle lead (B) on

potentiometer.

(5) Slowly rotate potentiometer shaft fully one

direction and then back the other.
Meter should show a smooth
decrease in resistance. If reading becomes
erratic replace potentiometer (refer to para 4.16
or 4.17).

increase or

B. Check Voltage (VDC)

Figure 2-9. Testing Potentiometers

Go To Table Of Contents

(1) Remove seat upholstery or appropriate covers

to access back or base potentiometer (refer to
para 4.16 or 4.17).

WARNING

Use caution to prevent electrical shock
with chair plugged into outlet. Electrical

components and connections are exposed.

(2) Plug chair into outlet.

(3) Set meter to read voltage DC on scale appropri-

ate to read approximately 5 VDC.

(4) Place meter probes (1, Fig. 2-9) on two outside

leads (A) of potentiometer (2).
Reading should be approximately 5 VDC
(±1 VDC).
If voltage reading is zero (0), leads are broken
in wire harness between potentiometer and P.C.
board or P.C. is not working correctly (Refer to
Troubleshooting Guide, Table 2-1).

SECTION II

TESTING AND TROUBLESHOOTING

© Midmark Corporation 2000 SF-1620 Page 2-5 Printed in U.S.A.

SECTION II

Go To Table Of Contents

TESTING AND TROUBLESHOOTING

2.3 Troubleshooting Procedures

Table 2-1 is a Troubleshooting Guide which is used to
determine causes of malfunctions. Refer to diagrams in
Section V to assist in troubleshooting procedures.

Problem Symptom Probable Cause Check Correction

Chair will not operate
when any
selected (from any of the
membrane switch pan­els or foot control
switches).

function is

When a membrane touch­pad or foot control switch is
pressed, nothing happens
and relays cannot be heard
energizing).

Power cord is not plugged
into facility wall outlet.

Facility circuit breaker pro­viding power to chair is
tripped.

Wire connections are loose. Check all wiring connec-

Fuse blown. Remove fuse, F1, F2,

PC circuit board is malfunc­tioning.
(Note: Incoming Line volt­age is present at Power
Input, J19, pins 2 [Blue] & 4
[Brown].)

WARNING

Use extreme caution when testing com-

ponents with chair plugged into outlet.
Line voltage is present. Failure to comply could
result in personal injury.

Check to see if power
cord is plugged in.

Check to see if facility cir­cuit breaker is tripped.
Plug a lamp into wall out­let that chair was plugged
into and see if it oper­ates.

tions from power cord to
PC circuit board. Use a
multimeter to perform
continuity checks on
wires.
Check for line voltage at
plug J19 (line power
input) on pins 2 (blue) &
4 (brown).

and F3 from PC board
and check fuses for conti­nuity.

Check for 12 VDC on
pins 1 & 2 of J14.

Check the LED’s next to
related relay when the
specific function is being
operated.

Plug power cord into facility
wall outlet.

If facility circuit breaker is
tripped, determine what
caused circuit breaker to trip,
correct problem, and then
reset / replace circuit breaker.

Clean any dirty connections.
Tighten any loose connec­tions. Replace any damaged
connections. Refer to Section
V for Schematics.

Replace blown fuse with fuse
of same rating. Refer to Sec­tion V for Schematics.

If no 12 VDC is present on J14
replace board.

If LED’s do not light during
function, replace board.

Chair has
functions can be initiated
from membrane touchpad
and foot control.

© Midmark Corporation 2000 SF-1620 Page 2-6 Printed in U.S.A.

Rev. 8/01

power, but no

Plug connector(s) loose or
wire harnesses broken.

SW1 Switch on PC Board is
set in Calibration Mode (both
switches 1 & 2 are ON)

Check visually for dam­age components and
broken traces on PC
board.

Check all plug connec­tors and harnesses.

Check settings on SW1
Switch.

If damage is visible replace
board. Refer to para 4.14.

Repair or replace malfunction­ing plug connector(s) or wire
harnesses. Refer to Section V
for Schematics.

Place SW1 switch settings in
proper position for user’s
application. Refer to Section V,
SW1 Switch Settings.

Problem Symptom Probable Cause Check Correction

Go To Table Of Contents

Chair will not operate
when any
selected (from any of the
membrane touchpads or
foot control switches).

(continued)

function is

Chair has
functions can be initiated
from membrane touchpad
and foot control. (contin­ued)

power, but no

TESTING AND TROUBLESHOOTING

PC Board malfunctioning.
(Note: Incoming Line volt­age is present at Power
Input, J19, pins 2 [Blue] & 4
[Brown].)

Check for 12 VDC on
pins 1 & 2 of J14.

Check the LED’s next to
related relay when the
specific function is being
operated.

SECTION II

If no 12 VDC is present on J14
replace board.

If LED’s do not light during
function, replace board.

One or more functions

be initiated from

cannot
membrane touchpad or
foot control.

BACK UP function does
not work.

Some functions can be ini­tiated with membrane
touchpad or foot control,
but at least one cannot.

When any BACK UP but­ton is depressed, chair will
not move (all other func­tions work).

Switch on Membrane Touch­pad or Foot Control is mal­functioning.

Wires Broken or connections
loose .

Capacitor for hydraulic pump
motor weak or bad. (Up
functions would not work)

PC Board malfunctioning.
(Note: Incoming Line volt­age is present at Power
Input, J19, pins 2 [Blue] & 4
[Brown].)

BACK or BASE potentiome­ter plug is loose from specific
potentiometer or wire leads
are broken.

BACK or BASE potentiome­ter is out of adjustment.

BACK and / or BASE
Potentiometer is damaged.

BACK UP solenoid coil has
an open winding, discon­nected or broken lead.

BACK UP solenoid valve
stuck in closed position .

Check visually for dam­age components and
broken traces on PC
board.

Perform a continuity
check on each N.O. con­trol switch in control
(when switch is pressed,
switch circuit should be
closed) Refer to Section
V for Schematics.

Check all wiring and
related connections
between control switches
and PC circuit board.

Replace capacitor with a
known good capacitor
and check operation.

Check for 12 VDC on
pins 1 & 2 of J14.

Check the LED’s next to
related relay when the
specific function is being
operated.

Check visually for dam­age components and
broken traces on PC
board.

Check conditions of plug
connectors and wire
leads to potentiometers.

Check adjustment of
BASE and/or BACK
potentiometer(s).

Check potentiometer(s).
Refer to para 2.2.

Check all wires to BACK
UP Solenoid and connec­tions at P.C. Board, pins
2 & 3 on J18. Check
solenoid for an “open”
coil. Refer to Section V
for Schematics.

After checking solenoid
coil , connections, and
wires, assure coil is ener­gized when depressing
BACK UP.

If damage is visible replace
board. Refer to para 4.14.

If control switch does not pass
continuity check, replace con­trol. Refer to para 4.6 or 4.21.

Clean any dirty connections.
Tighten or repair any loose or
damaged connections. Refer
to Section V for schematics.

Replace capacitor. Refer to
para 4.10.

If no 12 VDC is present on J14
replace board.

If LED’s do not light during
function, replace board.

If damage is visible replace
board. Refer to para 4.14.

Connect plug to potentiome­ter or repair broken leads.
Refer to Section V for sche­matic.

Adjust potentiometer. Refer to
para(s) 4.16, 4.17 or 4.18.

Replace potentiometer(s).
Refer to para(s) 4.16, 4.17 or

4.18.

Repair wires and / or connec­tions.
Replace Hydraulic Solenoid
Valve Assembly. Refer to para

1

3.

4.

Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

© Midmark Corporation 2000 SF-1620 Page 2-7 Printed in U.S.A.

Rev. 08/01

SECTION II

Go To Table Of Contents

TESTING AND TROUBLESHOOTING

Problem Symptom Probable Cause Check Correction

BACK UP function does
not work. (continued)

BACK DOWN function
does not work.

When any BACK UP but­ton is depressed, chair will
not move (all other func­tions work). (continued)

When any BACK DOWN
button is depressed, chair
will not move (all other
functions work).

Throttle Valve (TV3) on
Hydraulic Solenoid Valve
Assembly turned in too far or
completely closed.

Hydraulic BACK cylinder
leaking.

Hydraulic Solenoid Valve
Assembly is clogged pre­venting fluid flow.

BACK potentiometer plug is
loose from potentiometer or
wire leads are broken.

BACK potentiometer is out of
adjustment.

BACK Potentiometer is dam­aged.

PC Board malfunctioning. When BACK UP is

Safety Bail Limit Switch(es)
harness not installed cor­rectly (loose).

Safety Bail Limit Switch(es)
contacts open due to an
obstruction hitting cover or
Switch(es) malfunctioning,
stuck open

BACK DOWN solenoid coil
has an open winding, dis­connected or broken lead.

BACK DOWN solenoid valve
stuck in closed position .

Check position of TV3
Throttle Valve. Refer to
para 4.13 and BACK UP
hydraulic schematic in
Sect. V.

Check for leakage
around hydraulic cylin­der and fittings. Check for
excessive fluid returning
to reservoir from Vent
line.

Check for hydraulic fluid
flow to Back Cylinder dur­ing operation. Refer to
Section V for Schemat­ics.

Check conditions of plug
connectors and wire
leads to potentiometer.

Check adjustment of
BACK potentiometer.

Check potentiometer.
Refer to para 2.2.

depressed, check LED
next to K4 contacts to
assure it is lit. Check for
line voltage at J18, termi­nals 2 & 3. Refer to Sec­tion V for Schematics.

Check both harness to
assure they are con­nected tightly.

Safety Bail cover
depressing safety bail
limit switch(es) actuator,
opening contacts on
switch.
Check continuity on
unoperated switch to
assure normally closed
(NC) contacts are closed.

Check all wires to BACK
DOWN Solenoid and
connections at P.C.
Board, pins 4 & 5 on J18.
Check solenoid for an
“open” coil. Refer to Sec­tion V for Schematics.

After checking solenoid
coil , connections, and
wires, assure coil is ener­gizes when depressing
BACK DOWN.

Adjust Throttle Valve (TV3).
Refer to para 4.13.

Replace Hydraulic Back Cylin­der. Refer to para 4.7.

Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

Connect plug to potentiome­ter or repair broken leads.
Refer to Section V for sche­matic.

Adjust potentiometer. Refer to
para 4.17 or 4.18.

Replace potentiometer. Refer
to para 4.17 or 4.18.

If no voltage is present at J18,
terminals 2 & 3, when BACK
UP is depressed, replace PC
Board. Refer to para 4.14.

Connect harness correctly.

Remove obstruction that
causes cover to actuate limit
switch(es).
Replace Safety Bail Limit
Switch(es). Refer to para

4.19.

Repair wires and / or connec-

ns.

o

ti
Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

© Midmark Corporation 2000 SF-1620 Page 2-8 Printed in U.S.A.

Rev. 08/01

Problem Symptom Probable Cause Check Correction

Go To Table Of Contents

BACK DOWN function
does not work. (contin-

ued)

BASE UP function does
not work.

When any BACK DOWN
button is depressed, chair
will not move (all other
functions work). (contin­ued)

When any BASE UP but­ton is depressed, chair will
not move (all other func­tions work).

TESTING AND TROUBLESHOOTING

Throttle Valve (TV4) on
Hydraulic Solenoid Valve
Assembly turned in too far or
completely closed.

Hydraulic Solenoid Valve
Assembly is clogged pre­venting fluid flow.

Cuspidor Limit Switch con­tacts open due to cuspidor
hitting obstruction or mal­function.

Cuspidor not installed and
Jumper wire on J10 plug
connector missing.

BACK potentiometer plug is
loose from potentiometer or
wire leads are broken.

BACK potentiometer is out of
adjustment.

BACK Potentiometer is dam­aged.

PC Board malfunctioning. When BACK DOWN is

BASE UP solenoid coil has
an open winding, discon­nected or broken lead.

BASE UP solenoid valve
stuck in closed position .

Throttle Valve (TV1) on
Hydraulic Solenoid Valve
Assembly turned in too far or

letely closed.

p

com

Hydraulic BASE cylinder
leaking.

Check position of TV4
Throttle Valve. Refer to
para 4.13 and BACK
DOWN hydraulic sche­matic in Sect. V.

Check for hydraulic fluid
flow from Cylinder to
Reservoir during opera­tion. Refer to Section V
for Schematics.

Check if cuspidor is hit­ting obstruction and/or if
limit switch contacts
are open.

Check for a jumper wire
on P.C. Board plug con­nector J10.

Check conditions of plug
connectors and wire
leads to potentiometer.

Check adjustment of
BACK potentiometer.

Check potentiometer.
Refer to para 2.2.

depressed, check LED
next to K5 contacts to
assure it is lit. Check for
line voltage at J18, termi­nals 4 & 5. Refer to Sec­tion V for Schematics.

Check all wires to BASE
UP Solenoid and connec­tions at P.C. Board, pins
2 & 3 on J17. Check
solenoid for an “open”
coil. Refer to Section V
for Schematics.

After checking solenoid
coil , connections, and
wires, assure coil is ener­gized when depressing
BASE UP.

Check position of TV1
Throttle Valve. Refer to
para 4.13 and BASE UP
hydraulic schematic in
Section V.

Check for leakage
around hydraulic cylin­der and fittings. Check for
excessive fluid returning
to reservoir from Vent
line.

SECTION II

Adjust Throttle Valve (TV4).
Refer to para 4.13.

Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

Remove obstruction.
Replace Cuspidor limit switch.
Refer to ProCenter® Delivery
System Service & Parts.

Install a jumper wire on termi­nals 1 & 2, plug connector
J10. Refer to Section V for
Schematics.

Connect plug to potentiome­ter or repair broken leads.
Refer to Section V for sche­matic.

Adjust potentiometer. Refer to
para 4.17 or 4.18.

Replace potentiometer. Refer
to para 4.17 or 4.18..

If no voltage is present at J18,
terminals 4 & 5, when BACK
DOWN is depressed, replace
PC Board. Refer to para 4.1.

Repair wires and / or connec­tions.
Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

Adjust Throttle Valve (TV1).
Refer to para 4.13.

Replace Hydraulic Base Cylin­der. Refer to para 4.7.

© Midmark Corporation 2000 SF-1620 Page 2-9 Printed in U.S.A.

Rev. 08/01

SECTION II

Go To Table Of Contents

TESTING AND TROUBLESHOOTING

Problem Symptom Probable Cause Check Correction

BASE UP function does
not work. (continued)

BASE DOWN function
does not work.

When any BASE UP but­ton is depressed, chair will
not move (all other func­tions work). (continued).

When any BASE DOWN
button is depressed, chair
will not move (all other
functions work).

Hydraulic Solenoid Valve
Assembly is clogged pre­venting fluid flow.

PC Board malfunctioning. When BASE UP is

Safety Bail Limit Switch(es)
harness not installed cor­rectly (loose).

Safety Bail Limit Switch(es)
contacts open due to an
obstruction hitting cover or
Switch(es) malfunctioning,
stuck open

BASE DOWN solenoid coil
has an open winding, dis­connected or broken lead.

BASE DOWN solenoid valve
stuck in closed position.

Throttle Valve (TV2) on
Hydraulic Solenoid Valve
Assembly turned in too far or
completely closed.

Hydraulic Solenoid Valve
Assembly is clogged pre­venting fluid flow.

Cuspidor Limit Switch con­tacts open due to cuspidor
hitting obstruction or mal­function.

Cuspidor not installed and
Jumper wire on J10 plug
connector missing.

BASE potentiometer plug is
loose from potentiometer or
wire leads are broken.

Check for hydraulic fluid
flow to Back Cylinder dur­ing operation. Refer to
Section V for Schemat­ics.

depressed, check LED
next to K2 contacts to
assure it is lit. Check for
line voltage at J17, termi­nals 2 & 3. Refer to Sec­tion V for Schematics.

Check both harness to
assure they are con­nected tightly.

Safety Bail cover
depressing safety bail
limit switch(es) actuator,
opening contacts on
switch.
Check continuity on
unoperated switch to
assure normally closed
(NC) contacts are closed.

Check all wires to BASE
DOWN Solenoid and
connections at P.C.
Board, pins 4 & 5 on J17.
Check solenoid for an
“open” coil. Refer to Sec­tion V for Schematics.

After checking solenoid
coil , connections, and
wires, assure coil is ener­gizes when depressing
BASE DOWN.

Check position of TV2
Throttle Valve. Refer to
para 4.13 and BASE
DOWN hydraulic sche­matic in Sect. V.

Check for hydraulic fluid
flow from Cylinder to
Reservoir during opera­tion. Refer to Section V
for Schematics.

Check if cuspidor is hit­ting obstruction and/or if
limit switch contacts
are open.

Check for a jumper wire
on P.C. Board plug con­nector J10.

Check conditions of plug
connectors and wire
leads to potentiometer.

Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

If no voltage is present at J17,
terminals 2 & 3, when BASE
UP is depressed, replace PC
Board. Refer to para 4.1.

Connect harness correctly.

Remove obstruction that
causes cover to actuate limit
switch(es).
Replace Safety Bail Limit
Switch(es). Refer to para

4.19.

Repair wires and / or connec­tions.
Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

Adjust Throttle Valve (TV2).
Refer to para 4.13.

Replace Hydraulic Solenoid
Valve Assembly. Refer to para

4.13.

Remove obstruction.
Replace Cuspidor limit switch.

er t

o ProCenter® Delivery

Ref
System Service & Parts.

Install a jumper wire on termi­nals 1 & 2, plug connector
J10. Refer to Section V for
schematic.

Connect plug to potentiome­ter or repair broken leads.
Refer to Section V for sche­matic.

© Midmark Corporation 2000 SF-1620 Page 2-10 Printed in U.S.A.

Rev. 08/01

Problem Symptom Probable Cause Check Correction

Go To Table Of Contents

BASE DOWN function
does not work. (contin-

ued)

BASE DOWN and BACK
DOWN functions do not
work.

BASE UP and BACK UP
functions do not work.

When any BASE DOWN
button is depressed, chair
will not move (all other
functions work). (contin­ued)

When BASE DOWN and
BACK DOWN buttons are
pressed, chair will not
move. BASE UP and
BACK UP functions work.

When BASE UP and
BACK UP buttons are
depressed, chair will not
move. BASE DOWN and
BACK DOWN functions
work.

TESTING AND TROUBLESHOOTING

BASE potentiometer is out of
adjustment.

BASE Potentiometer is dam­aged.

PC Board malfunctioning. When BASE DOWN is

Safety Bail Limit Switch(es)
harness not installed cor­rectly (loose).

Safety Bail Limit Switch(es)
contacts open due to an
obstruction hitting cover or
Switch(es) malfunctioning,
stuck open

Cuspidor Limit Switch con­tacts open due to cuspidor
hitting obstruction or mal­function.

Cuspidor not installed and
Jumper wire on J10 plug
connector missing.

Internal thermal overload on
hydraulic motor pump open
due to running continuously
or weak or malfunctioning
overload.

Hydraulic Fluid in reservoir
low.

Capacitor on motor pump
weak or inoperative.

Low voltage is being sup­plied to chair.

Check adjustment of
BASE potentiometer.

Check potentiometer.
Refer to para 2.2.

depressed, check LED
next to K3 contacts to
assure it is lit. Check for
line voltage at J17, termi­nals 4 & 5. Refer to Sec­tion V for schematic.

Check both harness to
assure they are con­nected tightly.

Safety Bail cover
depressing safety bail
limit switch(es) actuator,
opening contacts on
switch.
Check continuity on
unoperated switch to
assure normally closed
(NC) contacts are closed.

Check if cuspidor is hit­ting obstruction and/or if
limit switch contacts
are open.

Check for a jumper wire
on P.C. Board plug con­nector J10.

Check continuity
between white & red
motor leads and yellow
and red leads. Refer to
Section V schematics.

Check reservoir for
hydraulic fluid level.

Replace capacitor with
known good capacitor of
same rating.

Check voltage at wall
receptacle - should be
between 110.0 to 126.0
VAC on 115 VAC units or
220 to 252 VAC on 230
VAC units.

SECTION II

Adjust potentiometer. Refer to
para 4.16.

Replace potentiometer. Refer
to para 4.16.

If no voltage is present at J17,
terminals 4 & 5, when BASE
DOWN is depressed, replace
PC Board. Refer to para 4.1.

Connect harness correctly.

Remove obstruction that
causes cover to actuate limit
switch(es).
Replace Safety Bail Limit
Switch(es). Refer to para

4.19.

Remove obstruction.
Replace Cuspidor limit switch.
Refer to ProCenter® Delivery
System Service & Parts.

Install a jumper wire on termi­nals 1 & 2, plug connector
J10. Refer to Section V for
schematic.

Allow motor to cool for 10 min­utes and recheck continuity. If
overload resets inform opera­tor that motor is for intermittent
operation Running continu­ously for a 30 second period
will cause overload to open.

overload does not reset

f

I
replace hydraulic motor pump.
Refer to para 4.9.

Fill reservoir to correct level..
Refer to para 4.12.

Replace capacitor. Refer to
para 4.10.

Correct low voltage situation
at wall receptacle.

© Midmark Corporation 2000 SF-1620 Page 2-11 Printed in U.S.A.

Rev. 08/01

SECTION II

Go To Table Of Contents

TESTING AND TROUBLESHOOTING

Problem Symptom Probable Cause Check Correction

BASE UP and BACK UP
functions do not work.

(continued)

BASE drifts down. BASE drifts down from ele-

BACK drifts down. BACK drifts down from ele-

Hydraulic Motor Pump
continues to run.

Chair doesn’t operate
correctly under heavier
loads.

BASE DOWN travel is too
slow.

When BASE UP and
BACK UP buttons are
depressed, chair will not
move. BASE DOWN and
BACK DOWN functions
work. (continued)

vated position.

vated position.

Depressing specific func­tion button, hydraulic motor
pump continues to run
when chair reaches top or
bottom limitations.

Chair moves slowly or not
at all under heavier loads.

Chair exceeds normal
second descent time from
top position to bottom posi­tion w/ 180 lbs (82 kg)
on it.

15

load

Hydraulic motor pump elec­trical leads disconnected.

Hydraulic motor pump has
open winding(s).

Pressure relief valve open or
leaking

BASE Hydraulic cylinder
leaking past piston seals.

BACK Hydraulic cylinder
leaking past piston seals.

BACK or BASE potentiome­ter plug is loose from specific
potentiometer or wire leads
are broken.

BACK or BASE potentiome­ter is out of adjustment.

Potentiometer is damaged. Check potentiometer(s).

Capacitor for Hydraulic
Motor Pump is weak.

Low voltage is being sup­plied to chair.

Leakage past pressure relief
valve.

Hydraulic cylinder(s) leaking
past piston seals.

Throttle Valve (TV2) is
turned in too far restricting
hydraulic fluid flow back to
reservoir.

Check electrical connec­tions on PC Board at J16,
terminals 2 & 3.

Check resistance values
of motor windings. Refer
to Section V for sche­matic.

Check if fluid is returning
to reservoir when BASE
UP and / or BACK UP
functions are activated
with no or normal load on
chair.

Check for excessive fluid
returning to reservoir thru
vent tubing of BASE cyl­inder.

Check for excessive fluid
returning to reservoir thru
vent tubing of BACK cyl­inder.

Check conditions of plug
connectors and wire
leads to potentiometers.

Check adjustment of
BASE and/or BACK
potentiometer(s).

Refer to para 2.2.

Replace capacitor with
known good capacitor of
same rating.

Check voltage at wall
receptacle - should be
between 110.0 to 126.0
VAC on 115 VAC units or
220 to 252 VAC on 230
VAC units.

Check for excessive fluid
flowing back to reservoir.

Check for excessive fluid
returning to reservoir thru
vent tubing of cylinder(s).

Check setting of Throttle
Valve (T V2 )

Reconnect electrical leads to
J16 on PC Board. Refer to
Section V Schematics.

Replace Hydraulic Motor
pump. Refer to para 4.9.

Replace Solenoid Valve
Assembly. Refer to para 4.13.

Replace BASE hydraulic cylin­der. Refer to para 4.8.

Replace BACK hydraulic cylin­der. Refer to para 4.7.

Connect plug to potentiome­ter or repair broken leads.
Refer to Section V for sche­matic.

Adjust potentiometer. Refer to
para(s) 4.16, 4.17 or 4.18.

Replace potentiometer(s).
Refer to para(s) 4.16, 4.17 or

4.18.

Replace capacitor. Refer to
para 4.10.

Correct low voltage situation
at wall receptacle.

olenoid

Replace Hydraulic
Valve Assembly. Refer to para

4.13.

Replace hydraulic cylin­der(s). Refer to para 4.7 and /
or 4.8.

Adjust Throttle Valve (TV2).
Refer to para 4.13 (Adjust­ments).

S

© Midmark Corporation 2000 SF-1620 Page 2-12 Printed in U.S.A.

Rev. 08/01

SECTION II

Go To Table Of Contents

TESTING AND TROUBLESHOOTING

Problem Symptom Probable Cause Check Correction

BASE DOWN travel is too
fast.

BACK DOWN travel is too
slow.

BACK DOWN travel is too
fast.

Hydraulic Pump is
exceedingly noisy.

Headrest difficult to
adjust or does not stay in
position.

Rotational Brake not
working.

Chair descends faster then

l 15 second descent

norma

time from top position to
bottom position w/ 180 lbs
(82 kg) load on it.

Chair exceeds normal
second descent time from
top position to bottom posi­tion w/ 180 lbs (82 kg)
on it.

Chair descends faster then

l 15 second descent

norma

time from top position to
bottom position w/ 180 lbs
(82 kg) load on it.

Noisy motor pump during
BACK UP or BASE UP.

Excessive force is required
to position the headrest.

Headrest does not lock into
a position or slides down­ward on own.

Brake is off, but chair top is
binding when rotated.

Brake lever is difficult to
engage.

Chair top rotates when
BRAKE lever is in locked
position.

15

load

Throttle Valve (TV2) is open
too far.

Throttle Valve (TV4) is
turned in too far restricting
hydraulic fluid flow back to
reservoir.

BACK lift spring(s) detached
or broken.

Throttle Valve (TV4) is open
too far.

Restriction in Suction line
from reservoir causing nega­tive pressure.

Internal parts failure in motor
pump.

Headrest slide is too tight
and needs adjusted.

Headrest slide is too loose
and needs adjusted.

Brake is out of adjustment
(needs loosened).

Brake is out of adjustment
(needs loosened).

Brake is out of adjustment
(needs tightened).

Check setting of Throttle
Valve (TV2).

Check setting of Throttle
Valve (T V4 )

Check conditions of
BACK lift spring(s).

Check setting of Throttle
Valve (TV4).

Check for kinks in tubing
and / or restrictions in
suction line.

Check for noise or vibra­tions from motor pump
during operation.

Check adjustment of
headrest slide.

Check adjustment of
headrest slide.

Check adjustment of
brake.

Check adjustment of
brake.

Check adjustment of
brake.

Adjust Throttle Valve (TV2).
Refer to para 4.13 (Adjust­ments).

Adjust Throttle Valve (TV4).
Refer to para 4.13 (Adjust­ments)

Connect or replace BACK lift
spring(s).

Adjust Throttle Valve (TV4).
Refer to para 4.13 (Adjust­ments).

Repair or replace tubing.

Replace motor pump. Refer to
para 4.9.

Adjust the headrest slide
assembly. Refer to para 4.4.

Adjust the headrest slide
assembly. Refer to para 4.4.

Adjust brake. Refer to para

4.5.

Adjust brake. Refer to para

4.5.

Adjust brake. Refer to para

4.5.

© Midmark Corporation 2000 SF-1620 Page 2-13 Printed in U.S.A.

Rev. 03/10

SECTION II

Go To Table Of Contents

TESTING AND TROUBLESHOOTING

© Midmark Corporation 2000 SF-1620 Page 2-14 Printed in U.S.A.