Sharp R-210A, Service Manual

R-210A

10

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

CAUTION: 1˚C CORRESPONDS TO 60 WATTS. REPEAT MEASUREMENT IF THE POWER IS

INSUFFICIENT.

1 l

1 l

(T1  C)

(T2  C)

1 l

1 l

(T1  C)

(T2  C)

CARRY OUT 3D CHECKS.

A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set to the highest

resistance range.

C. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10M

Ω

after it has been charged.

D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 M

Ω

 because of its internal 10M

Ω

resistance.

D

HIGH VOLTAGE CAPACITOR TEST

B

POWER TRANSFORMER TEST

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:

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.

If the reading obtained are not stated as above, then the power transformer is probably faulty and
should be replaced.
CARRY OUT 4R CHECKS.

a.Primary winding ................ 0.5 ohms approximately

b.Secondary winding ........... 107  ohms approximately

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

C

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

Ω

 in the other direction.

CARRY OUT 4R CHECKS.

NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF

THE MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS, BE-
CAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIREC-
TIONS.

B

C

HIGH VOLTAGE RECTIFIER

Heat up for 2 min. 22 sec.