Printed Circuit Board; Circuit Check Procedure - Frigidaire MFM-6D Service Manual

PRINTED CIRCUIT BOARD

1. CIRCUIT CHECK PROCEDURE

1) Low Voltage Transformer (DMR-604P) Check.
The low voltage transformer is located on the P.C.B.
Measuring condition: Input voltage: 120V
1
2
NOTE 1: Secondary side voltage of the low voltage transformer changes in proportion to fluctuation
of power source voltage.
NOTE 2: The allowable tolerance of the secondary voltage is within ±5% of norminal voltage.
2) Voltage Check
Key check point
NO. CHECK POINT
1 IC1 PIN 6, 10, 11
2 IC1 PIN 1
3 IC1 PIN 22
4 IC1 PIN 8 or 9
5 DP1 PIN 1 & 25
CHECK METHOD
MEASURE POINT
NO.
1 MP1
2 MP2
3 MP3
NOTE : Each measure point must be measured with GND points.
43
Frequency: 60Hz
10
8
7
6
–5VDC
–30VDC
0V
-14V
0V
-5V
2.4 VAC (DISPLAY FILAMENT VOLTAGE)
WAVE FORM
DC –5V ± 0.25
DC –30V ± 1.0
DC –27V ± 1.0
Voltage
Terminal
6–7
8–10
REMARK
T
T
T: 250ns
REMEDY
Replace ZD2, EC1, EC2
Replace R21, ZD3
Replace R21, R22, EC5
LOAD NO LOAD
24V 30V
2.4V 2.5V
T: 16.67 ms (60 Hz)
REMARK
NO LOAD
NO LOAD
NO LOAD