Service manual

R-3S68

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

6. Measure the final water temperature. (Example: The final temperature T2 = 21°C)

7. Calculate the microwave power output P in watts from above formula.

Initial temperature .................................................................................................. T1 = 11°C

Temperature after (49 + 2) = 51 sec. ..................................................................... T2 = 21°C

Temperature difference Cold-Warm.................................................................... ∆T1 = 10°C

Measured output power

The equation is “P = 85 x ∆T” ...................................................... P = 85 x 10°C = 850 Watts

JUDGMENT: The measured output power should be at least ± 15 % of the rated output power.

CAUTION: 1°C CORRESPONDS TO 85 WATTS REPEAT MEASUREMENT IF THE POWER IS

INSUFFICIENT.

1000g

T1˚C

T2˚C

Heat up for 51 sec.

B POWER TRANSFORMER TEST

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 of the high-voltage

circuits, including the magnetron filament.

CARRY OUT 3D CHECKS.

Disconnect the leads to the primary winding of the power transformer. Disconnect the filament and

secondary winding connections from the rest of the HV circuitry. Using an ohmmeter, set on a low range,

it is possible to check the continuity of all three windings. The following readings should be obtained:

a. Primary winding ....................approx. 1.4 Ω

b. Secondary winding ...............approx. 98 Ω

c. Filament winding ...................less than 1Ω

If the reading obtained are not stated as above, then the power transformer is probably faulty and should

be replaced.

CARRY OUT 4R CHECKS.

C HIGH VOLTAGE RECTIFIER ASSEMBLY TEST

HIGH VOLTAGE RECTIFIER TEST

CARRY OUT 3D CHECKS.

Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier can be tested

using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C of the high

voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading.

The normal resistance is infinite in one direction and more than 100 kΩ in the other direction.