Sharp R-4A54

R-4A54
R-4A54B
TEST PROCEDURES (CONT’D)
PROCEDURE
LETTER COMPONENT TEST
1 ooog
+
T2”C
Heat up for 49 sec.
(RD82u03Ul
M
PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING
BOARD (PWB) IS OPEN.
To protect the electronic circuits, this model is provided with a fine foil pattern added to the
primary on the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the trou-
bleshooting guide given below for repair.
Problem: POWER ON, indicator does not light up.
/STEPS :
OCCURANCE
1
CAUSE OR CORRECTION
/ 1
/
/
/The rated AC voltage is not present at POWER ter- j Check supply voltage and oven power cord. Please /
j minal of CPU connector (CN-A)
j I
use term “Low voltage transformer” when refering to I
’ transformer Tl
I
j 2
I
/ The rated AC voltage is present at primary srde of low Low voltage transformer or secondary circuit defec- j
1 voltage transformer.
tive Check and repair.
I
I Only pattern at “a” is broken.
; ‘Insert jumper wire Jl and solder.
I
; 4
/ Pattern at “a” and “b” are broken.
I
I ‘Insert the coil RClLF2003YAZZ between “cl’ and
1
/
: “d”.
M
RELAY TEST
NOTE:’ At the time of these repairs, make a visual in-
spection of the varistor for burning damage
and examine the transformer with tester for the
presence of layer short-circuit (check primary
coil resistance).
If any abnormal condition IS detected, replace
the defective parts.
1. CARRY OUT 30 CHECKS
2. Disconnect the leads from the primary of the power transfomer. Make sure that the leads re-
main isolated from other oven components and chassis. (Use insulation tape if necessary.)
3. Close the door.
4. Reconnect the supply.
5. Check the voltage between Pin Numbers 3 and 5 of 4-pin connector (A) on the control unit
with an A.C. voltmeter. The meter should indicated 240 volts, if no check oven circuit.
6. RYl AND RY2 TEST
These are operated by D.C. voltage. Check voltage at relay coil with a D.C. voltmeter during
the microwave cooking operation.
DC. voltage indicated . . . . . . . . . . . . . . . . . . . . Defective relay
DC. voltage not indicated .
. . . . . . . . . . . . Check diode which is connected to the relay coil. If di-
ode is good, control unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE
CONNECTED COMPONENTS
RYl Approx. 26.5V. D.C.
Oven lamp/Turntable motor/Cooling fan motor
RY2 Approx. 25.8V.D.C.
Power transformer
7