Merrychef Mealstream 400 Service Manual

Page 1 400 Series Ovens 32Z3769 Issue 1

CAUTION MICROWAVE EMISSIONS

DO NOT BECOME EXPOSED TO EMISSIONS FROM THE MICROWAVE

GENERATOR OR PARTS CONDUCTING MICROWAVE ENERGY

SERVICE MANUAL

Mealstream 400

SERVICE MANUAL

For all 400 Series models manufactured from February 2009

Part No. 32Z3769 Issue No. 1

SERIES

Merr ychef

Page 2 400 Series Ovens 32Z3769 Issue 1

Merrychef Limited,
Station Road West,
Ash Vale, Aldershot
Hampshire GU12 5XA
United Kingdom

Tel: [phone] Fax: [phone]
Internet address: http://www.merrychef.com

E-mail: [e-mail] or [e-mail]

Table of Contents

Safety Code ...................................................................................................3

Product Specifications ................................................................................... 4

Installation Instructions ..................................................................................5

Electrical Installation ......................................................................................6

Error Codes and Diagnostics.........................................................................7

Main Features................................................................................................8

Electronic Controls.........................................................................................9

Power Output Testing to EN 60335-2-90.....................................................10

Power Transformer Test ..............................................................................10

High Voltage Capacitor Test........................................................................11

High Voltage Rectifier Test ..........................................................................11

Magnetron Test............................................................................................11

Door Interlock Operation........................................................................ 12-14

Casework.....................................................................................................15

Door Mechanism..........................................................................................16

Oven Cavity Components & Hot Air System ...............................................17

Oven Door Assembly ...................................................................................18

Door Interlock RHS, Magnetron & Stirrer motor ..........................................19

Principal components LHS & Rear View .....................................................20

Principal components RHS 1: Models _EE5, _XE5 [CD2] ..........................21

Principal components RHS 2: Models _EE5, _XE5 [CD2] ..........................22

Principal components RHS 3: Models _XX5, _XX52...................................23

Input Wiring, Filters and Fuses 1 .................................................................24

Input Wiring, Filters and Fuses 2 .................................................................25

Control Panel 1: Electronic Controls............................................................26

Control Panel 2: Membrane Panel circuit ....................................................27

Control Panel 3: Manual Control assembly .................................................28

Part No. Identification ........................................................................... 29-30

Appendix 1 MenuKey Download Procedure ................................................31

Appendix 2 Cleaning Procedure ..................................................................32

Recommended Parts List (Spares)........................................................34334

Circuit Diagrams .................................................................................... 35-38

Merrychef and MenuKey™ are registered Trademarks of Merrychef Ltd.

For Service contact:

Page 3 400 Series Ovens 32Z3769 Issue 1

This manual is designed to assist engineers who have been on a recognised product familiarisation
and training course run by Merrychef Limited. It has been prepared to offer technical guidance for the
Merrychef Mealstream 400 range of Combination Microwave Ovens.

Please remember that it is wiser not to attempt a service task if you are unsure of being able to
complete it competently, quickly, and above all safely.

To avoid injury to yourself, and to protect the appliance from possible damage, please follow this
Safety Code when servicing these ovens.

Before attempting to repair the oven, check it for microwave leakage.
Check that the oven is not emitting microwaves, even when supposedly not

in operation.
Check that the oven is not operating continuously, whether the display

indicates cooking or not.
Always discharge the HT capacitors before working on the oven using a

suitably insulated 10 MΩ Resistor

Before removing the rear cover from the oven ensure you do the following:

• Switch off the mains supply and remove the plug from the wall socket.

or

• If the oven is hard wired, ensure that the power is turned off at the isolator switch.

Note: the On/Off switch on the oven is not adequate protection against electric shock, as it does

not isolate all of the internal wiring from the Electrical Supply.

Upon completion of a service on a Mealstream 401/403 oven, or before reconnecting the appliance
to the mains supply for testing, check all of the following points:

• All internal electrical connections are correct.

• All wiring insulation is correct and is not touching a sharp edge.

• All Earth connections are electrically and mechanically secure.

• All four door safety interlocks are secure and mechanically sound.

• The door operation is smooth, and the arms run freely in the slots.

• The door activates all four of the door interlock switches in the correct order.

• All fuse-holder safety covers are correctly fitted.

• The temperature sensor is correctly connected to the Power PCB.

Before finishing the service call, recheck the following points:

• All of the electronics are functioning correctly, and all of the touch pads are working.

• The turntable is rotating correctly.

• The power output of the oven is correct (see pages 12 & 13 ).

• Microwave emission is below permissible limit - 5 mW/cm² (see BS EN 60335-2-90).

• Oven has correct 50mm air gap all round and 150mm above.

Air flow should not be restricted.

SAFETY CODE

Page 4 400 Series Ovens 32Z3769 Issue 1

Power
Requirements

See RATING PLATE on rear of oven

Power Output
(IEC 705)

Microwave 100%
Convection
Combination

700W (_EE, _XE)
3000W (_XX5 )
700W + 1500W ( _EE )
700W + 3000W ( _XE )
1000W + 3000W ( _XX5 )

External
Dimensions

Height
Width
Depth

530 mm (Plus 150 mm minimum clearance above)
550 mm (Plus 50 mm minimum clearance each side)
575 mm (Plus 50 mm clearance behind)

Internal
Dimensions

Height
Width
Depth
Turntable
Capacity

315 mm
330 mm
330 mm
300 mm Diameter

34.3 litres

Weight Nett

Gross packed

All models except XX5 45kg, XX5 55kg
All models except XX5 58kg, XX5 68kg

Construction Cavity

Casework

Stainless Steel
304 Stainless Steel
Anodised Aluminium Extrusions

Settings Microwave

Temperature
Timer

100%,75%,50%,25%, Convection only
Off, 175°C, 200°C, 225°C, 250°C, 275°C
Up to 30 minutes

Up to 3 cooking stages of up to 30 minutes each
(Programmed)

Model No.: 1003 + Voltage + Frequency + Current + Controls

Model
prefix

Voltage

Frequency

Current Control

Type

2 = 220-230V a.c.
4 = 230-240V a.c.

5 = 50 Hz
6 = 60 Hz

EE = 13A 5 =

Series 5

controls

1003

XE = 30A
XX = 30A

Supply

Phase

2=

Twin

Phase

MenuKey

MK

Catalytic

converter*

C

ELECTRONIC CONTROLS: ( EC401 & EC403 models )

Model No.: 1003 + Voltage + Frequency + Current

Model prefix Voltage Frequency Current

1003

2 = 220-230V a.c.
4 = 230-240V a.c.

5 = 50 Hz
6 = 60 Hz

CD2 = 13amp
XD2 = 30amp

MANUAL CONTROLS ( CD & XD models )

For example: 100345XE52MK

230-240V, 50Hz, 30A, Series 5 Controls, Twin Phase, MenuKey

Product specifications: Mealstream 401 & 403 models

+ Phase + MenuKey + Catalytic converter

* A Catalytic converter is fitted to Mealstream 403 models only

Page 5 400 Series Ovens 32Z3769 Issue 1

Positioning the Oven

In order to maintain adequate ventilation for air intake and exhaust, and to allow access for
cleaning the air filters, you must allow a minimum of 50mm(2 inches) clearance at the sides
and rear of the oven, and at least 150mm above.
Air intake temperature should not exceed 35°C (95°F).
Excessive temperature will lead to reduced operating duty cycle or premature ageing of
internal components.

NEVER Install an oven above fryers, grills, griddles or any other major heat source.
NEVER Stack machines on top of each other - always use a double stand.
ALWAYS Place containers in the cavity carefully - impact damage may chip the

vitreous enamel coating.

Installation instructions

Page 6 400 Series Ovens 32Z3769 Issue 1

Models 1003__XE52, 1003__XX52

WARNING

All models ( 30A ) must be connected to a separate electrical supply rated at
30 Amps by a qualified and approved electrician. A suitable 30 amp rated
isolating switch with a 3mm contact gap on both poles should be fitted for each
oven installed.

Establishments with standard ( Type ‘B’ ) circuit breakers are sensitive to ‘surges’ which occur
on switching on freezers, refrigerators and other catering equipment, including microwave
ovens. Because of this, we strongly recommend that a separate Type ‘C’ circuit breaker
( designed specifically for this type of equipment ) must be fitted. An individual, suitably rated
circuit breaker should be fitted for each oven installed.

TWIN PHASE

The Mealstream 401 oven Twin Phase models
should be connected as shown in Diagram 2.
The Circuit Breaker should be rated at 20A per phase
(TypeC).

Electrical installation:

WARNING: This appliance must be earthed.

Failure to do so may result in electric shock and death

Where an approved and fitted moulded plug is
supplied we strongly recommend that this plug is
never removed.
However certain establishments may require a
different plug to be fitted. In this case, the wiring
instructions shown should be observed.

Models 1003__EE5, 1003__CD2
The power outlet used must be individually fused. It
is essential that the socket is properly installed and
earthed. It should be fed from a circuit which is
suitable for high power electrical appliances and it is
important that this circuit is not overloaded.

Models 1003__XE5, 1003__XD, 1003__XX5
When supplied, single phase models are fitted with a
Blue 32Amp Plug approved to BS4343. Wiring cable
colours as shown in Diagram 1

The Circuit Breaker should be rated at 45A (TypeC).

Diagram 1

Diagram 2

Simplified loading Diagram

Page 7 400 Series Ovens 32Z3769 Issue 1

Error codes and diagnostics

Electronic Control Models
The control panel will identify some of the most common problems by flashing an error
message code in the time display window.

Error Message

Possible Cause Service

1

2

Door not fully shut

Possible electrical fault

Close door fully.

Check Microswitch Door Circuit
Check Microswitch Connection to PCB
Check Ribbon Cable
Check Relay PCB & Logic PCB

1
2
3
4

5

No time has been set
Invalid time has been set
Invalid program has been set
Number pad failure

Memory Failure running a Program

Set a time
Set a valid time
Use call-back to check program
(Menukey: no key downloaded)
Membrane key short circuit
Re-Program Pad,
if fault repeats replace Logic PCB

1 Oven is not at correct temperature

to start program

Allow oven to reach correct
Programmed temperature

1 MenuKey removed before the

download is complete
or the process has been
interrupted

Switch oven off and begin the MenuKey
download again

1 Magnetron overheated Air inlet on rear of machine being obstructed.

High air inlet temperature.
Slow running cooling fan, jammed turntable or
broken gearbox
(cooling fan also drives turntable _XE5 models)
Faulty magnetron overheat ‘stat or associated
wiring.

1 Jumper installed incorrectly on

PCB logic board

Check Jumper position

1

2

Magnetron has overheated but
has now recovered
Internal diagnostic fault

Check that magnetron cooling fan and turntable
are working correctly
Check installation, air inlet temperature and air

filters

1 Oven control area is overheating Check air filters.

Check axial fan
Check installation for hot air intake

EPS= External Program System

Error Light Operation

The “Air Filter Blocked” light and “Service” light are triggered by the internal circuitry. If the magnetron
overheats, the error code “E:7” or “E:8” is displayed on the front panel, and both the “Air Filter Blocked”
and the “Service” indicators will light. Once the magnetron has cooled sufficiently to allow the oven to
restart, the “Service” light will remain illuminated until the oven is turned off.

This fault may have been triggered by one of the following causes:

- Air inlet on rear of machine being obstructed.

- High air inlet temperature.

- Slow running cooling fan, jammed turntable or broken gearbox
(note: cooling fan also drives turntable on EE5, CD2 and XE5 models).

- Faulty magnetron overheat ‘stat or associated wiring.

Note that the customer may not have noticed that the oven displayed “E:7” or “E:8”, and so the
reported fault may be misleading.

[Service]

[Air Filter blocked]

Page 8 400 Series Ovens 32Z3769 Issue 1

b VENTS

c TRAY HANDLE RESTS

There is one on each side of the oven for
convenient storage of the tray handle.

d BAFFLE PLATE

Forms the inside rear of the oven and covers the
hot air circulation fan. Removable for cleaning by
unscrewing the four wing nuts which hold it in
place. This must be cleaned on a regular basis,
and kept free of debris.

CATALYTIC CONVERTOR

Allows extraction free cooking. Should be
removed regularly for cleaning. ( Do not spray/
put caustic cleaner directly into the catalytic
converter as this will cause permanent damage )

e RUNNERS

These mounted on each side of the oven cavity
to support the rectangular racks or oven trays,
and are for use in CONVECTION MODE ONLY.

f HOT AIR FAN

Situated behind the baffle plate, and circulates
the hot air through the baffle plate, over the
heating element, and around the edge of the
baffle plate back into the cavity.

g OVEN CAVITY

The oven cavity is stainless steel. It must be kept
clean See CLEANING.

h TURNTABLE TRAY

The vitreous enamelled turntable tray fits onto the
turntable disc in the bottom of the oven cavity,
and rotates during cooking to ensure an even
distribution of microwave energy so that the food
is cooked evenly.

j RATING PLATE

The rating plate is situated on the rear of the
oven, and states the Model, Serial Number,
Electrical Ratings and Manufacturers Tel no.

k DOOR

The door consists of a thermally insulated inner
section, and an additional air gap provided by a
twin skinned door front to lower the surface
temperature.

l ON/OFF SWITCH

This is used to turn the oven On or Off.
IT DOES NOT ISOLATE INTERNAL WIRING
FROM THE ELECTRICAL SUPPLY.

n ELECTRICAL SUPPLY LEAD

p AIR FILTER

Main intake for cooling air for internal
components. Must be clear of obstructions.

q MenuKey

Main features

b

c

d

e

f

g

h

j

k

l

m

p

n

q

rear view of Oven

Page 9 400 Series Ovens 32Z3769 Issue 1

Electronic controls:

a Stage LED's

b Service Indicator

c Air Filter Block Indicator

e Program Display

f Temperature Set Pads

g Time / Program Number Pads

h Cancel/ Callback Pad

i Program Pad

j Convection Pad

k Microwave power Pads

l On/Off switch

m MenuKey socket

i

j

a

b

c

e

f

g

h

k

l

m

Page 10 400 Series Ovens 32Z3769 Issue 1

Procedure B - Simplified Power Output Test for Field Service Use

You will need:

A thermometer capable of reading to ±0.1°C.
A Polypropylene tray approximately 200 mm x 200 mm.
A measuring jug.
A calculator.
Water which is at a temperature of 10°C ± 2°C.

1 Measure 1 litre of cold water into the tray using the measuring jug.
2 Measure the water temperature, and record it as T[s].
3 Place the tray on the turntable in the oven and close the door.
4 Turn the oven on.
5 Set the timer to 1:02. ( For Manual controls use a stopwatch set to 1 minute 2 seconds )
6 Press the “100%” power pad.
7 When the oven bleeps, open the door and remove the tray.
8 Stir the water thoroughly, and measure its temperature. Record this as T[e].

Calculation:

1 T[r] = T[e] - T[s].
2 Power = 70 x T[r]. Power is in Watts.

The power given by the above test should be within ±10% of the rated power.

Procedure C - Power Transformer Test

You will need:

A Digital Multi-meter (D.M.M.)
A Megger or similar resistance meter using 500V d.c.

1 Isolate the oven from the mains supply.

WARNING: High voltages and large currents are present at the secondary winding and filament

winding of the Power Transformer. It is very dangerous to work near this part when the
oven is on. NEVER make any voltage measurements at the High Voltage circuits,
including the magnetron filament.

WARNING: Even when the oven is not cooking, the Po wer Transformer has High Voltages presen t

because of the Soft Start circuit. Isolate the oven before testing.

a Mains winding between tags

Approx. 1.3 Ω

b High Voltage winding

Approx. 50-100 Ω

c Filament winding

between terminals

Less than 1 Ω

Primary winding and chassis

Pass if over 10 MΩ

Filament winding and chassis

Pass if over 10 MΩ

2 Ensure that the High Voltage Capacitor is discharged before commencing work.
3 Remove all connections from the Power Transformer.
4 Using a D.M.M., check the continuity of the windings. Results should be as follows:

5 Using a Megger, test the insulation resistance between:

One end of the High Voltage winding is connected to the

chassis, so this is not tested.

a

c

b

Procedure A - Power Output Test In accordance
with BS EN 60335-2-90 is not used in the field please

Engineers Procedure B.

Page 11 400 Series Ovens 32Z3769 Issue 1

Procedure E - High Voltage Rectifier Test

You will need:

A Megger or similar resistance meter using 500V d.c.

WARNING: High voltages and large currents are present at the High Voltage Rectifier. It is very

dangerous to work near this part when the oven is on. NEVER make any voltage
measurements at the High Voltage circuits, including the magnetron filament .

WARNING: Even when the oven is not cooking, the High Voltage Rectifier has High Voltages

present because of the Soft Start circuit. Isolate the oven before testing.

Procedure D - High Voltage Capacitor Test

You will need: A Digital Multi-meter (D.M.M.)

A Megger or similar resistance meter using 500V d.c.

5. Using a Megger, test the insulation resistance between the
terminals and the case.

1. Isolate the oven from the mains supply.

2. Ensure that the High Voltage Capacitor is discharged before
commencing work.

3. Remove all connections from the High Voltage Capacitor.

4. Using a D.M.M., check for continuity between the terminals &

WARNING: High voltages and large currents are present at the High Voltage Capacitor. It is very

dangerous to work near this part when the oven is on. NEVER make any voltage

measurements at the High Voltage circuits, including the magnetron filament .

WARNING: Even when the oven is not cooking, the High Voltage Capacitor has High Voltages

present because of the Soft Start circuit. Isolate the oven before testing.

Between Terminals

Pass if approximately 10 MΩ

Between Terminals and Case Pass if open circuit

Between Terminals and Case

Pass if over 100 MΩ

Procedure F - Magnetron Test

You will need:

A Megger or similar resistance meter using 500V d.c.

A Magnetron can be tested for an open filament or a short circuit
by carrying out a continuity check.

1. Isolate the oven from the mains supply.

2. Ensure that the High Voltage Capacitor is discharged before

commencing work.

3. Remove all connections from the Magnetron.

4. A continuity check across the Filament terminals should be 1ohm or less

5. A continuity check between each filament terminal and the

metal outer should read open.

1. Isolate the oven from the mains supply.

2. Ensure that the High Voltage Capacitor is

discharged before commencing work.

3. Remove all connections from the High Voltage

Rectifier.

4. Using the Megger, test for continuity in both

directions. Compare results with the table.

Open Circuit both ways

FAIL

Conducts one way only

PASS

Short Circuit both ways

FAIL

Conducts one way, leaks the other

FAIL

Page 12 400 Series Ovens 32Z3769 Issue 1

SW2 Primary Interlock— located on the left hand side of the oven. Directly disconnects

the supply to the microwave generating circuit and thereby cuts off the microwave emissions
from the oven when the door is opened.

SW1 Monitored switch—located on the same assembly as the primary. The Monitor

switch will produce a short circuit across the mains supply if the Primary interlock switch is
faulty, thus blowing the microwave fuse and rendering the oven inoperative.

SW3 The Secondary interlock—located on the left hand side of the oven and like the

primary switch will cut off the microwave emission and will do so even if the primary and
monitored interlock have failed open circuit.

Note: If operation of the Monitor switch has caused the Microwave Fuse to blow, the

Primary and Monitor microswitches must be changed, as they may have been
damaged by the high short-circuit currents involved.

SW4 Convection fan switch—located on the same bracket as the control switch.

This switch is wired in series with the convection motor supply and will disconnect when
the door is opened.

SW5 Control switch—located on the top right behind the display connects to the

logic control PCB on a black and white twisted pair of wires. It is this signal that is used by

the control circuit to determine the door position. A closed contact indicates a closed door.

Door interlock operation

The door on the oven is monitored by five microswitches. Three of these are used in the
conventional “Primary, Secondary and Monitor” switch arrangement shown below, while the fourth
is a low-voltage switch linked directly to the control circuitry and the fifth switches the power to the
convection motor.The switches operate as follows:

Door open position

Fused

Live

Live

LHS

RHS

Control PCB

Convection Fan

Neutral

Neutral

Output

SW2 Primary

SW5

SW4

SW3 Secondary

SW1 Monitor