Merrychef Mealstream 500 Service Manual

Page 1 Mealstream Ovens 32Z3387 Issue 3

CAUTION MICROWAVE EMISSIONS

DO NOT BECOME EXPOSED TO EMISSIONS FROM THE MICROWAVE

GENERATOR OR PARTS CONDUCTING MICROWAVE ENERGY

SERVICE MANUAL

Mealstream 500

SERVICE MANUAL

For all Mealstream 501, 502 & 503 models manufactured

from January 2001 & Tim Hortons Models

Part No. 32Z3387 Issue No.3

Merr ychef

Page 2 Mealstream Ovens 32Z3387 Issue 3

Table of Contents

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

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

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

Error Codes and Diagnostics.................................................6

Main Features........................................................................7

Electronic Controls ................................................................8

Manual Controls ....................................................................9

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

Power Output Testing..........................................................11

Power Transformer Test......................................................11

High Voltage Capacitor Test......... .... ... ................................12

High Voltage Rectifier Test............................ .... ..................12

Magnetron Test ...................................................................12

Principal components LHS..................................................13

Principal components RHS..................................................14

Principal components Top...................................................15

Principal components Cavity Roof and Door.......................16

Principal components Cavity...............................................17

Principal components ( not shown in main views ) .............18

Input wiring..........................................................................19

Interlock Operation..............................................................20

Electronic Control Panel Assembly .....................................21

Manual Controls Panel Assembly........................................22

Membrane Panel Circuit......................................................23

Complete Spare Part Listing.......................................... 24-25

Electrical Diagrams ....................................................... 26-27

Appendix 1: MenuKey Download Procedure.......................28

Appendix 2: Cleaning procedure................................... 29-30

Appendix 3: PCB Connection Points............................. 31-33

Appendix 4: Transformer upgrade.................................. .... .34

Appendix 5 Hot air motor replacement... ...................... 35-39

Appendix 6: Temperature sensor replacement ...................40

Appendix 7: Fuse change FLM020 Type....................... 41-42

Appendix 8: Tim Hortons .............................................. 44-47

Appendix 9: Door interlock set-up procedure ................ 48-52

Manual corrections and modifications.................................53

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]

Page 3 Mealstream Ovens 32Z3387 Issue 3

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 501 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 mains.

Upon completion of a service on a Mealstream oven, or before reconnecting the appli ance to the
mains supply for testing, check all of the following points:

• All internal electrical connections are correct (see wiring diagram Pages 26-27).

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

• All Earth connections are electrically and mechanically secure.

• All 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 three of the door interlock switches in the correct order.

• 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 power output of the oven is correct.

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

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

Air flow should not be restricted.

• Clean air filters are in place.

SAFETY CODE

Page 4 Mealstream Ovens 32Z3387 Issue 3

Power
Requirements

Refer to rating Plate

Power Output:
CTM3

CTM5

Microwave 100%
Convection
Combination
Convection
Combination

1425W (IEC 705)
2500W
1425W + 2500W
3000W
1425W + 3000W

External
Dimensions

Height
Width
Depth

640mm (Plus 50mm minimum clearanc e ab ove)
710mm (Plus 50mm minimum clearance each side)
630mm (Plus 50mm clearance behind)

Internal
Dimensions

Height
Width
Depth
Capacity

260mm
490mm
360mm

45.86 litres (1.62 ft³)

Weight Nett

Gross packed

90kg
106kg

Construction Cavity

Casework

304 Stainless Steel

Settings Microwave

Temperature
Timer

100%,75%,50%,25%, Convection only
Off, 150°C, 175°C, 200°C, 225°C, 250°C
Up to 30 minutes
Up to 3 cooking stages of up to 30 minutes each
Programmed (Series 5)

Model Number: CTMx v f c p MK C

Example CTM524505MK

Mealstream EC501, High speed fan
230-240V, 50Hz, Series 5 electronic controls & MenuKey

CTMx
Fan Speed

v
Voltage

f
Frequency c Control Type p Phase

MK
MenuKey

22 = 220-230V EU
24 = 230-240V UK

50 = 50 Hz
60 = 60 Hz

5 = Electronic

CD2 = Rotary Dial

Controls

2 = 2 phase
1 = 1 phase

Omitted

MK =
MenuKey
fitted

CTM3 =
Low speed
CTM5 =
High speed

C
Catalytic
Converter

C=

EC503
Catalytic
Converter

Product specifications:

Page 5 Mealstream Ovens 32Z3387 Issue 3

Installation Instructions for Mealstream 500 series Combination Ovens

Power Supply Requirements

The Mealstream 500 series oven should be connected to a suitable electricity supply, which
can cope with the switching-on surge that occurs with certain types of catering equipment, such
as microwaves. Because of t his requirement, we strongly recommend that a separate, suitably
rated supply is installed for the oven.

The supply for the oven should be fitted with a Type "C" circuit breaker, rated at:
30 Amp for Mealstream 500 Series (all models)
If the oven is hard-wired to the supply, a double-pole isolator switch with a contact gap of at

least 3mm should be fitted and positioned close to the oven to allow the oven to be moved for
servicing.

Positioning the Oven
In order to maintain adequate ventilation for air intake and exhaust, and to allow access for

cleaning filters, you must allow a minimum of 50mm clearance at the sides and rear of the
oven, and at least 50mm above. Air intake temperature should not exceed 35°C - excessive
temperature will lead to reduced operating duty cycle or premature ageing of internal
components.
Failure to comply with these conditions will invalidate the warranty.

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 on the runners and baffle plate.

Installation instructions:

50mm 50mm

50mm

50mm

350mm

Page 6 Mealstream Ovens 32Z3387 Issue 3

Models with electronic controls 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
2

Oven not heating up
Possible Heater circuit fault

Check heater fuse

Confirm operation of heater, overheat

stat and heater circuit

1 Oven Cavity overheating Check cavity sensor

Confirm heater relay is operating

1 Oven is not at correct

temperature to start program
Operator Error !!

Allow oven to reach correct

Programmed temperature

1 Oven control area is

overheating.

Check air filters

Check axial fan

Check installation for hot air intake

MenuKey removed before the

download is complete
or the process has been
interrupted.

Switch oven off and begin the MenuKey

download again.

Error codes and diagnostics

Page 7 Mealstream Ovens 32Z3387 Issue 3

a On/Off SWITCH

This is used to turn the oven On or Off.

IT DOES NOT IS OLATE INTERNAL WI RING
FROM THE MAINS SUPPLY.

b HOT AIR VENTS

Allows steam and excess pressure to escape

from the oven cavity. It must be kept clear.

c OVEN CAVITY

The oven cavity is mainly constructed from
stainless steel panels. It must be kept clean.

d BAFFLE PLATE

EC501 Models:
The convection fan draws air ov er the heating
element into the cavity over the edges of the rear
baffle plate producing perfect heat distribution for
combination cooking. The met al grill covering the
fan must be kept clean and free of debris.
502 & 503 Models:
The convection fa n, which is located behind the
cavity filter pulls air in throu gh the cataly tic
converter which removes the majority of the smoke
from the air flow.

e RUNNERS

These are 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.
CTM3_ Low speed Fan
CTM5_ High Speed Fan

g RATING PLATE

The rating plate is situated on the rear of the
oven, and states the Model, Serial Number,
Electrical Ratings and Manufacturers telephone
number.

h 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.
It is important that the choke plate and the slots
are free from debris.

i DOOR SEAL
j MAINS LEAD

k AIR FILTERS

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

l MenuKey

m STEAM OUTLET

Main features:

a

m

c

d

e

f

h

j

g

k

i

b

k

b

l

back panel

Page 8 Mealstream Ovens 32Z3387 Issue 3

a Stage LED's
b Program & Time Display
c Service Indicator
d Air Filter Block Indicator
e Convection Pad

f Power Pads
g Time / Program Number Pads
h Temperature Set Pads

i Cancel / Callback Pad

j Program Pad
k MenuKey socket

Electronic controls:

a

b

f

g

i

j

d

h

e

c

k

Page 9 Mealstream Ovens 32Z3387 Issue 3

a Power Neon ( Amber )
b Temperature Control
c Power Control
d Timer
e Start Push button

f Cook cycle Neon ( Red )

g Heater Neon ( Amber )

a

g

Manual controls:

f

e

merrychef

Mealstream CD

2

START

TIME

POWER %TEMP °C

b

c d

Page 10 Mealstream Ovens 32Z3387 Issue 3

Procedure A - Power Output Test in accordance with
BS EN 60335-2-90 Annex AA

This test is given in the BSI test standard for microwave ovens. It is reproduced below - not so that
you can follow it, but to show you why it is impractical in normal conditions. A simplified procedure,
which gives a good approximation to the BSI power output, is given in Procedure B which follows.

Note: This test can only be car ried out on a COLD oven. If the oven has been operating, even for
only a few seconds, the power given will be lower than the oven rating. This test must also be carried
out at a stable voltage - the voltage in most kitchens varies considerably even within the period of the
test. If the oven has been operating, go to Procedure B.

You will need:

A thermometer capable of reading to ±0.1°C.
A cylindrical borosilicate glass container, 190 mm diameter, with a wall thickness of

3 mm or less.

A calculator.
A set of scales capable of reading 1kg to an accuracy of ± 1g.
A glass or plastic stirrer.
A jug capable of holding over 1 litre of water.
Drinkable water which is at a temperat ure of 10°C ± 1°C.
A “Variac” or similar variable transformer capable of supplying the oven to ensure a

stable voltage.

WARNING: The Borosilicate Glass container has thin walls and is therefore fragile

- take care not to break it during use.

Method
A cylindrical container of borosilicate glass is used for the test. It has a maximum thickness of
3mm, an external diameter of approximately 190mm and a height of approximately 90mm. The
mass of the container is determined.

At the start of the test, the oven and the empty container are at ambient temperature. Potable water
having an initial temperature of 10°C ± 1°C is used for the test. The temperature of the water is
measured immediately before it is poured into the container.

A quantity of 1000g ± 5g of water is added to the container and its actual mass obtained. The
container is then immediately placed in the middle of the oven base. The appliance is supplied at
rated voltage and operated at the maximum power setting. The time for the water temperature to
attain 20°C ± 2°C is measured. The oven is then switched off and the final water temperature is
measured within 60seconds.

NOTES:

1 The water is stirred before its temperature is measured.
2 Stirring and measuring devices are to have a low heat capacity.

The microwave power output is calculate d from the formula:

4.187 M

W

(T2-T1) + 0.55 MC (T2-T0)
P =
t
where

P is the microwave power output, in watts;
M

W

is the mass of the water, in grams;

M

C

is the mass of the container, in grams;

T

0

is the ambient temperature, in °C;

T

1

is the initial temperature of the water, in °C;

T

2

is the final temperature of the water, in °C;

t is the heating time in seconds, excluding the magnetron filament heat-up time.

Page 11 Mealstream Ovens 32Z3387 Issue 3

Procedure B - Simplified Power Output Test

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 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 n ot cooking, the Power Tr ansformer has High Volt ages present

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. 82 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

For Tim Hortons
see APPENDIX 8

Page 12 Mealstream Ovens 32Z3387 Issue 3

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 13 Mealstream Ovens 32Z3387 Issue 3

Note A: see page 17 for parts

14

12

Left side

10

13

11

1A

2A

3A

6

1

2

3

4A 4

7

9

8

No Description EC 501/2/3 RD 501

1 Fuse holder 30Z0231 30Z0231
1A Fuse 10 amp 30Z0217 30Z0217
2 Fuse holder 30Z0231 30Z0231
2A Fuse 10 amp 30Z0217 30Z0217
3 Fuse holder 30Z0231 30Z0231
3A Fuse 1 amp 30Z0957 30Z0957
4 Fuse holder 30amp ( FLM Series )B 30Z1178 30Z1178
4A Fuse 20 amp Littlefuse FLM020B 30Z1177 30Z1177
6 Mains terminal block 31Z0149 31Z0149
7 Filter ( Heater circuit ) 30Z0997 30Z0997
8 Filter ( Microwave circuit ) 30Z0997 30Z0997
9 Door spring short 520000 520000

9 Door spring long 40C1141 40C1141
10 Door arm stop assembly 11C0279 11C0279
11 Microswitch ( Primary ) 30Z0240 30Z0240
12 Door hinge assembly ( LH )A 11C0167 11C0167
13 Door arm assembly 11C0300 11C0300
14 Microswitch ( Monitor ) 30Z0240 30Z0240

Principle components:

Note B: see appendix for models before March 2004

Page 14 Mealstream Ovens 32Z3387 Issue 3

Right side

22

20

17

21

9 10

16

13

Note A: see page 17 for parts

Principle components:

No Description EC 501/2/3 RD 501

9 Door spring short

520000 520000

9 Door spring long

40C1141 40C1141

10 Door arm stop assembly

11C0279 11C0279

13 Door arm assembly

11C0300 11C0300

16 Door hinge assembly ( RH )A

11C0166 11C0166

17 Microswitch ( Secondary )

30Z0240 30Z0240

20 Steam pipe

790046 790046

21 Steam vent guard

790061 790061

22 Temperature sensorC

50E123 50E123

Note C: see appendix for models before March 2004

Page 15 Mealstream Ovens 32Z3387 Issue 3

23

23

24

25

28

27

24

25

27

26

26

Top view

62

60 61

No Description EC 501/2/3 RD 501

23 Magnetron 30Z0264 30Z0264
24 Resistor Gold 470 R 30Z0283 30Z0283
25 HT diode 11C0266 11C0266
26 Capacitor 1.1µF 30Z1077 30Z1077
27 Trans fo rmer 220 V 50Hz 30Z0083 30Z0083
27 Trans fo rmer 240 V 50Hz 30Z1018 30Z1018
28 Twin blower motor 310110 310110
60 25mm OD Flexible conduit 314402 314402
61 20mm OD Flexible conduit 314401 314401
62 Capacitor c lip 31Z0175 31Z0175

Principle components:

Page 16 Mealstream Ovens 32Z3387 Issue 3

Door & cavity roof

Principle components:

No Description EC 501/2/3 RD 501

67 Stirrer glass & long seals 40C0954 40C0954

67a Stirrer glass short side seal 790052 790052

71 Door seal kit 11C0292 11C0292
72 Door choke 790007 790007

67

67a

Air Filters

No Description EC 501/2/3 RD 501

81 Air filter panel (removable) 40C0868 40C0868

81

81

Note: for Tim Hortons see Appendix 8

72

71