Hi all,
I´ve been mostly a reader of this forum, and it rocks! But now i need help from you guys.
The TV arrived with only standby led lightning. I have found IC100 (L6599DTR) to be defective on the 24V and 12V power supply. Changed IC100. After changing IC100 i've got the following situation:
- Power supply has 5V Standby.
- TV sends signal to turn 24V and 12V on.
- Q501 turns on VCC.
- VCC is 14.8V.
- 12V reads 5.3V and 24V oscillates between.
- PFC is working (389V on C608).
What i've done so far:
- Measure capacitors on the output: OK!
- Measure shorts on 24V and 12V to ground: No shorts!
- Check feedback circuit on secondary side: No problems found.
- Changed Optocoupler even if the original was ok: No changes.
- Checked C112: Ok.
- Checked C113 on the ISEN line of IC100: Ok.
- Checked all resistors (throughole and snd): All ok.
Finally i swapped the power supply with a known good one and the tv works great, but that is from other tv that i cannot spare.
Can you guys give me some clues? Do i have to swap the ceramic smd caps that are surronding IC100, namely C117 who is responsible for the oscillator frequency? I suspect that because the transformer of the 24V and 12V is making a whinning noise...
For the records, if i put a load of 500 ohms on the 24V, the voltade drops 2V!!!
Thanks in advance.
Sorry for my poor English.
Greetings,
Retrorepair
P.S: already checked the diodes around IC100 and MOSFET's.
I´ve been mostly a reader of this forum, and it rocks! But now i need help from you guys.
The TV arrived with only standby led lightning. I have found IC100 (L6599DTR) to be defective on the 24V and 12V power supply. Changed IC100. After changing IC100 i've got the following situation:
- Power supply has 5V Standby.
- TV sends signal to turn 24V and 12V on.
- Q501 turns on VCC.
- VCC is 14.8V.
- 12V reads 5.3V and 24V oscillates between.
- PFC is working (389V on C608).
What i've done so far:
- Measure capacitors on the output: OK!
- Measure shorts on 24V and 12V to ground: No shorts!
- Check feedback circuit on secondary side: No problems found.
- Changed Optocoupler even if the original was ok: No changes.
- Checked C112: Ok.
- Checked C113 on the ISEN line of IC100: Ok.
- Checked all resistors (throughole and snd): All ok.
Finally i swapped the power supply with a known good one and the tv works great, but that is from other tv that i cannot spare.
Can you guys give me some clues? Do i have to swap the ceramic smd caps that are surronding IC100, namely C117 who is responsible for the oscillator frequency? I suspect that because the transformer of the 24V and 12V is making a whinning noise...
For the records, if i put a load of 500 ohms on the 24V, the voltade drops 2V!!!
Thanks in advance.
Sorry for my poor English.
Greetings,
Retrorepair
P.S: already checked the diodes around IC100 and MOSFET's.
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