5en aoc partially fixed
- From: "yhan" <cheian07@xxxxxxxxx>
- Date: 26 Jan 2006 00:31:21 -0800
hi there!!!
since there were no reply from the group, i just tried to repair the
monitor. it finally comes to life now.
Turned on the monitor. No signal yet from the video.
I measured the voltages in the low voltage psu. they seemed ok
(according to the information).But still, i replaced some capacitors
there. Then I measured the voltage on the HOT. 80v (same as with the
b+). Voltages coming from the main psu are present. Now turned on the
computer. After receiving video signal, the LED turns to green and a
presence of HV. But just seconds, the monitor pulses in sync with the
LED. Display too big and wide that also sync with the pulse. (Another
monitor here with the same model exhibits same behavior except that
there is no display then just stopped with green light on after several
pulses.) Turned off the monitor for a while, inspect cold solder.
Reflow with solder the suspected cold solder joints. Tested transistors
and other componets in the low voltage and horizontal area especially
HOT. Desolder the collector of HOT and tested voltage. Fine but no high
voltage of course! Everythings seemed fine. So next thing i did was to
disconnect the secondary load of the flyback. Still same behavior. Then
disconnected the crt board to eliminate CRT as a problem (i read about
crt short that loads down a supply). Still to no avail. I finally
conclude that it was the flyback which is the culprit. Get a known good
flyback from the same model (a little sacrifice was made because
flyback in this area is not so available especially for monitors) just
to confirm. Replace the flyback and the set came alive again. No
pulsing is heard. To confirm if there is high voltage already, wind a
wire in the flyback and measured. There is 6.5 volts. HV is present!
Now I noticed the pincushion is bad. This is my only problem now. Too
much width and hourglass shape.
Same thing happen to the other monitor w/ same brand. Its problem now
is very low heater voltage. Only 1 volt. ABL line is 1 volt also. I
measured the heater pin of the crt for short but its ok. i traced back
where the supply is coming from, its not from the flyback winding. i
think from the main psu. tested transistors. seems fine. Turned off and
disconnected the crt board. measure the voltage. It goes to normal. 6.3
volts DC. the ABL line's voltage also goes to normal. If i remember,
about 4 volts. Whenever i connect the crt board the crt, the voltage
goes down. So I disconnected the connection to the heater pins and wind
a wire two times from the flyback and connected it to the heater pins.
power on the switch but there no HV anymore! I measured again the
heater voltage. Now it becomes negative. Ah I dont know now.
Please provide me with information on how to fix the pincushion and
heater voltage problem that i am encoutering right now. Also please
give comments and constructive criticism about my repair procedure.
Thanks in advance.
looking forward to your reply,
ian b (philippines)
.
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