Toshiba 1997 G Series Handbuch zur Fehlersuche - Seite 12
Blättern Sie online oder laden Sie pdf Handbuch zur Fehlersuche für TV Toshiba 1997 G Series herunter. Toshiba 1997 G Series 28 Seiten. Color television power supply and shutdown
Seite drucken
7. Main Power Supply Troubleshooting
Guide
Poor Regulation:
The Main Power Supply is a looped circuit. In order to
troubleshoot the circuit, the loop must be broken. By
interrupting the feedback portion of the loop, it can be
determined if a problem exists in the primary or second-
ary side of the supply. Table 3 and 4 shows the switch-
ing frequencies of IC801 and the secondary voltages of
the supply with various feedbacks. If the main supply is
not regulating properly, open F470 and check the switch-
ing frequency of IC801. Using the tables below, inter-
rupt the feedback. If the frequencies are as shown, the
primary side of the power supply is good. If the fre-
quencies are off, the primary side of the power supply is
bad. Notice that once the feedback is interrupted, the
load has no bearring on the switching frequency.
If the problem is on the primary, C866, R864,
D872,C862, R866,C870 and IC801 should be checked.
If the proplem is on the secondary side, Q862, and Z801
should be checked.
100W light for a load
Good feedback
Open Feedback: Pins 3 & 4 of Q862
open.
Shorted feedback: Pins 3 & 4 of
Q862 shorted
3K Resistor feedback inplace of pins
3 & 4 of Q862.
No load
Good feedback
Open Feedback: Pins 3 & 4 of Q862
open.
Shorted feedback: Pins 3 & 4 of
Q862 shorted
3K Resistor feedback inplace of pins
3 & 4 of Q862.
Frequency at pin 14 of
IC801:
68Khz
60Hhz
138Khz
90Khz
Table 3
Frequency at pin 14 of
Seconday Voltage
IC801:
at F470:
136Khz
60Hhz
138Khz
90Khz
Table 4
10
Seconday Voltage
at F470:
124V
Engages Overvoltage
140v
protect on pin 9 of IC801
92V
103V
Notes:
140V
Engages Overvoltage
160V
protect on pin 9 of IC801
140V
174V
Notes: