Sharp Carousel R-980E Service Manual - Page 15

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PROCEDURE

LETTER

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

Temperature after (47 + 2) = 49 sec. ................................................................ T2 = 21 C

Temperature difference Cold-Warm ..............................................................

Measured output power

The equation is "P = 90 x T" ................................................. P = 90 x 10 C = 900 Watts

JUDGMENT: The measured output power should be at least

CAUTION: 1 C CORRESPONDS TO 90 WATTS REPEAT MEASUREMENT IF THE POWER IS

POWER TRANSFORMER TEST

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

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:

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

should be replaced.

CARRY OUT 4R CHECKS.

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 k in the other direction.

CARRY OUT 4R

ASYMMETRIC RECTIFIER TEST

CARRY OUT 3D CHECKS.

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

an ohmmeter set to its highest range across the terminals A+B of the asymmetric rectifier and note

the reading obtained. Reverse the meter leads and note this second reading. If an open circuit is

indicated in both direction then the asymmetric rectifier is good. If an asymmetric rectifier is shorted

in either direction, then the asymmetric rectifier is probably faulty and must be replaced with high

voltage rectifier. When the asymmetric rectifier is defective, check whether magnetron, high voltage

TEST PROCEDURES

INSUFFICIENT.

1000g

T1˚C

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.

a. Primary winding .................... approx. 1.2

b. Secondary winding ............... approx. 66

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

CHECKS.

COMPONENT TEST

Heat up for 49 sec.

ASYMMETRIC

RECTIFIER

T1 = 10 C

15 % of the rated output power.

1000g

T2˚C

HIGH VOLTAGE RECTIFIER

R-980E