Samsung LE32S81B - missing standby voltage

[Sportline]

Good day, instead of Q0165R I mistakenly put 24C256 (don't ask me how) and made a short circuit. After I put Q0165R I don't have stand by voltage again. There is no voltage on the cold side. I found the schematic.

I checked a few things but didn't find anything. When I checked the DB802 diode, it showed a short circuit, but when I unsoldered one leg, it looked fine, and I still have a short circuit on its contacts. On the other side of the board, I have DZB801 also shorted, but it is SOT23, so I didn't remove it, do you think it could be connected to it? Could there be some protection in this marked transformer, how to check it? Or do you think that the ISM801(MC33067) is damaged, how can I check it (I don't have an oscilloscope), I looked at VCC to ground, it is not short circuited, but I have a small voltage on VCC, and the datasheet says 20V??? Is it the voltage after the TV is turned on?

Any help is welcome.

[Sportline]

Re: Samsung LE32S81B - missing standby voltage

I found a short circuit (marked in red on the diagram) it is DZB801 30Vz SOT23
After I connected the voltage to the board, I got stand by voltage.
I'm wondering if that diode is there only in terms of protection, will it work without it?
Ako je trebam zamjeniti kako da nađem oznaku?

[R_J]

Re: Samsung LE32S81B - missing standby voltage

The zener diode is required to regulate that voltage to not go above 30v, if it does the ic will be damaged. You should also replace that electrolytic CB802 (22µf/50v) next to it, they dry out over time.

[Sportline]

Re: Samsung LE32S81B - missing standby voltage

I'm bad with labeling these things, if you can help me, I took a better photo?

[R_J]

Re: Samsung LE32S81B - missing standby voltage

It seems to be a 18v zener, BZX84-C18 or Z02w18vy, Looking at the correct schematic, DZB801 is a 18v zener not a 30v zener
FSQ0165RN maximum VCC voltage = 20vdc

[lotas]

Re: Samsung LE32S81B - missing standby voltage

Yes, "Y6" - BZX84C18-V (18v).

[Sportline]

Re: Samsung LE32S81B - missing standby voltage

I finally got the diode, replaced it and the TV works, satisfied.
But my main problem that caused me to disassemble the TV is still there. When it turns on, it is amplified to max. more precisely at 300 and when you go to reduce the volume, a line remains on the screen as seen in the photo.
In addition, I also replaced all capacitors, one was bad.
Has anyone had a similar problem?

[lotas]

Re: Samsung LE32S81B - missing standby voltage

I don’t understand, when you turn on the TV, the volume is automatically increased to the maximum and when it is reduced, it again starts to increase to the maximum?

[Sportline]

Re: Samsung LE32S81B - missing standby voltage

Yes, the volume is more than 300 and when you go to reduce it to 301 it is like 1 and when you go to 299 it is again at max then at 201 it is like 1 at 199 it is again max and so on until you reach the normal scale 1-100 but this trace remains on the screen and is not deleted.

[lotas]

Re: Samsung LE32S81B - missing standby voltage

Try unplugging the keyboard from the motherboard and test with the remote.

[Sportline]

Re: Samsung LE32S81B - missing standby voltage

Tried, same story.

[lotas]

Re: Samsung LE32S81B - missing standby voltage

Try to put a clean eeprom 24c256.

[Sportline]

Re: Samsung LE32S81B - missing standby voltage

Try to put a clean eeprom 24c256.

That was my first plan, if you read my first entry it will be clear to you. But apparently I was stupid and went to look for the eeprom on the power board instead of the main one. It's my school and it looks like I had the wrong version, mine was with legs, and that's where the smd version goes.

[lotas]

Re: Samsung LE32S81B - missing standby voltage

You can unsolder it (25c256) from the board, save the data (dump) just in case, then erase it (so that all FF is in it) and solder it back.
But for this you need a programmer.

[Sportline]

Re: Samsung LE32S81B - missing standby voltage

Ok, thanks for the tip, I'll give it a try.