21SF8XEL 21" CRT TV ripped pads, PCB (kd -331 (v1.0) sh12144)

[R_J]

The flyback is likely ok, the sound is caused by a poor waveform. either the drive signal has a problem, or more likely a bad capacitor on one of the secondary voltages supplied by the flyback, there could also be a bad cap in the power supply secondary, 10 min fix with a scope 10 days by testing and swapping parts.
Replace all the electrolytics around the power supply and the flyback.

[GraphicMan]

Did you replace the capacitors I mentioned? another common capacitor to fail in these crt tv's is C307, this is the horz. drive transformer, filter cap, Again the locations I give you will be different on your chassis BUT they should be there if you follow the schematic.

Looks like the website ate the manual, here it is again, if the site loses it again, here is a link CHINA CRT TV TS2453 LA76932 LA78041 FSCQ1265 Service Manual download, schematics, eeprom, repair info for electronics experts (elektrotanya.com)

If you don't have proper service equipment, like a scope, all you can do is throw parts at it until it works.

yes i did replace all 3 caps around the STR, they are all 50v 10uF, they read fine with reasonable esr though, after replacing i noticed the tv show the screen a bit faster than before and i really thought i fixed the problem specially that i tried to warm that area before on the old caps and the screen shows right after that rather than a colt start,, so i kept testing (on/off) after few attempts it did not want to show a screen anymore and just goto sleep again however i want to give an important hint,

i did notice many times before (with and without the new caps) that there is indeed a faint scratchy interrupted sound and i think it is coming from the FBT (my best guess) while it is trying to show screen and one time with the new caps while tv working fine and showing a screen with no issue the sound appears again (instead of a uniform humming) it was like a wavy scratchy sound then i thought to shut it down, then it did not want to show a screen again on the next attempt, could it be a tiny inside FBT leakage/arcing? cant see any visible hole or arcing though

[CapLeaker]

Check the MLCC’s on the tcon.

[R_J]

Did you replace the capacitors I mentioned? another common capacitor to fail in these crt tv's is C307, this is the horz. drive transformer, filter cap, Again the locations I give you will be different on your chassis BUT they should be there if you follow the schematic.

Looks like the website ate the manual, here it is again, if the site loses it again, here is a link CHINA CRT TV TS2453 LA76932 LA78041 FSCQ1265 Service Manual download, schematics, eeprom, repair info for electronics experts (elektrotanya.com)

If you don't have proper service equipment, like a scope, all you can do is throw parts at it until it works.

[GraphicMan]

I noticed that sometimes when the tv shuts down the screen horizontally scales down a little first then shuts down completely, i checked a cap close to the vertical IC outside the board and it read good, what else could it be?

[GraphicMan]

The tv is working for longer times but it still goto standby , i tried to lower the brightness and contrast by a lot but it still shut down after few minutes or randomly , plz guide me where to check
thanks

[GraphicMan]

it looks like the main cap was the problem, i did replace it with a 450v 330uF instead the original 450v 150uF, according to my LCR the replacement was giving me 303uF but a bit less ESR, however it does have a belly on above and have been sitting for years with no use it looks like it did the trick, at the begining the tv did goto sleep but soon went back on by itself, the more i test the less the turning off, i know from experience that old caps need time to wake up again, only time will prove that
the other subject is that it seems like i cant find the right spots to measure voltages, all i was able to do is measuring the 5v and it was 7.4v dc
the other pads on the transformer (chopper i believe) are all giving me 0.2v, apparently i measuring in the wrong pad / pads, i was using the ground of the main cap, i shared a photo of the same model i have, can u point to me where i should probe? thanks a lot)

[GraphicMan]

What have you checked? have you checked any voltages? start by replacing the bad electrolytic capacitors in the primary of the power supply, you can't tell if components (caps) are bad just by looking at them. look at the schematic and replace the capacitors C509, C531, they will likely have different location numbers on your model.

yes the 300v is about 334v ( i think while on sleep) i have pulled out the biggest cap on the psu and measured it good, i can replace also just to make sure, it is difficult to measure the voltages while on because the tv now barely turns on, it just switch back to sleep almost instantly giving me no time to measure anything, i dont have the schematics , do you mean i should looks for C509 and C531 and replace then where they are? or they might have different numbers?

[R_J]

What have you checked? have you checked any voltages? start by replacing the bad electrolytic capacitors in the primary of the power supply, you can't tell if components (caps) are bad just by looking at them. look at the schematic and replace the capacitors C509, C531, they will likely have different location numbers on your model.

[GraphicMan]

Now i am at the original problem the customer was complaining from, which is the tv works sometimes and then goto standby , then might work again by itself and so on randomly,
what do you think specially that i did not find any blown nor a swollen cap

[GraphicMan]

The TV worked again directly after a correct trace reconstructions based on your suggestion, will let you know if there are any problems, so far so good, thank you very much

[GraphicMan]

This schematic uses the same FSCQ1265RT ic (page 17) so you should be able to compare, I would need a picture of that complete area to do a proper trace. See if pin 4 trace connects to the optocoupler, here is my best guess

yes indeed i agree with your assumption
i have shared a pic showing where is the opticoupler
now i need first to check that STR, see if it might be still good or bad, i know it is impossible to know for sure on cold testing but at least pass it
can you tell me how to test it for that?
thanks a lot for your help and time

[R_J]

This schematic uses the same FSCQ1265RT ic (page 17) so you should be able to compare, I would need a picture of that complete area to do a proper trace. See if pin 4 trace connects to the optocoupler, here is my best guess

[GraphicMan]

Hello
someone forced the STR (FSCQ1265RT) out and ripped the pads off
now I need to reconstruct the tracks but I dont know how it will go (no prior pics before the damage)
Attached the affected area pic, pic 2 is the best i could found online for the same area

the pins from 1 to 5 are for the STR
any help is appreciated
Thanks