Merrychef 501 Service Manual download pdf (Page 11)

Page 11 Mealstream Ovens 32Z3387 Issue 2

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 not cooking, the Power Transformer has High Voltages 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.

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Merrychef 501 Service Manual Page 11

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