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After changing again U9101 with a new one received from Aliexpress the board is working again and TV seems to be fine now!! That means that the IC U9101 from the Aliexpress board (having P02) was bad. I was about to abandon this board...
Tomorrow I'll test the TV for a few hours to see how it performs.
This week I will also receive a new replacement board and I wonder if it's good or bad )
I moved the transformer and nothing changed. The same alternating voltages from U9101:
- alternating from 1.5 to 5v (mainly at 3V)
- alternating from 9V to 13V
are also present on U9103 and U9102 optocuplers - PIN 4.
Not sure what to check any more, everything I test seems to be in order.
No, can this be responsible? is that the yellow one in the middle? I think I heard a buzzing sound from that one the last time when the parts were blown ...
Found out that on the new board P02 the +3.5/+5V connections are missing entirely nothing connected there, probably that circuit is not needed (that is for other Tv: NEC).
I moved the good circuits from this board to my board:
- Q9101 mosfet
- blown rezistors
- U9101 (3s121)
The outputs:
+3.5/+5V=0V
12VA/16VA, 12V/16V=-0.7V
All 3 mosfets on the hot side have on D: 320V.
Measuring the voltages on U9101 = 3s121 I have:
1=FB/OLP=alternating from 1.5 to 5v (mainly at 3V)
2=BR=~2.7V
4=ST=~320V
5=DRV=0V ...
New PSU:
Looking over to find the connections for +3.5/+5V, I found that the problems were usually tied to U9307 (for P01). This component is not present on this board.
I then looked and saw that this new board is actually: 715G7350-P02-000-002S
The diodes were checked, maybe the mosfet was damaged, I will re-check everything and try again when I will receive the components.
-------------------
New PSU:
In the mean time I ordered and received from AliExpress another PSU and of course it came faulty (and asked for a refund).
This new board is mainly the same with a few small changes. I have measured the outputs and this time:
-> 12VA/16VA, 12V/16V -> ~12V which is OK
-> +3.5/+5V -> ~0V
Nothing seems to be burned, checked the main diodes, everything seems to be in order....
I received the resistors, 3S121 and replaced them. The PSU was alive for a while only: 3V standby, but then I connected to the TV. The screen was on, worked, but had some red pixels all over screen (every approx 10 cm) + the big problem: a buzzing sound from the PSU.
It was a loud buzzing sound. The screen was on for 30 seconds and then the big white resistor blew (low resistance) already replaced, also with the Mosfet that was originally replaced, the 2 resistors just replaced and other 2 new resistors
I ordered the new type of resistors to try again...
Added pictures with...
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