Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

[kevinm34232]

As stated above it just flashes the red standby light every 2 seconds repeatedly, nothing else. Inspection of the PS board shows very high heat in the section to the left of the large caps between the heat sinks. Nothing obvious shorted. The large cap'(s) voltage is fluctuating from about 190v-220v while standby light flashes.

Any ideas where to start with this one? Thank you.

[CapLeaker]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

Sounds like this:

https://www.badcaps.net/forum/showth...hlight=samsung

Can you give a exact description on what your tv is doing or not doing?

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

It looks like there's a short on the main board, the 5V line.. I jumped the PS-ON and everything is good there. Haven't made any progress trying to find the short though.
I've tried freezing components but no luck there as it doesn't stay on long enough to get hot, and same with an external PS.. Any ideas?

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

Found the short on the B5V line but unfortunately did not fix the TV, all voltages present but TV does not turn on, no inverter_On from main board. Relay clicks every 40 secs. Thinking main CPU is bad.

[dskall]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

What is voltage between legs of main cap in standby and when you press power button

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

When you first plug in you get 163V at caps for a couple secs, relay clicks and PS turns on, voltage now 390V. It will stay here for 40 secs and repeat cycle. Power button does nothing. This is common with these models with a faulty main board, I've seen many and not found a fault so I've chalked it up to the CPU.

[CapLeaker]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

Found the short on the B5V line but unfortunately did not fix the TV, all voltages present but TV does not turn on, no inverter_On from main board. Relay clicks every 40 secs. Thinking main CPU is bad.

Me too

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

For what it's worth, the shorted component was either C115 or C903. I took them both off at once so not sure which one it was.

[dskall]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

So the fluctuating voltage of 190v-220v was not on main caps?

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

That was before finding the shorted SMD cap on main board. ^^^^

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

Can't resist the curiosity... Got a working board and tested the differences in voltages in this area.. Noticeably a problem between the 3.3v and 1.7v voltage regulators (see circled). Input/output on good one should be 3.3v/1.7v, but bad board is showing 2.5v/1.4v.

Is this worth trying to chase down? Every once in a while I see a quick backlight flash like it's trying to power on but then nothing..

[dskall]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

Does the regulator get hot? Might trace back your 3.3v. May have problem on 3.3v line

[attainteddragon]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

you could lift it off of the board and see if your 3.3v comes back up.

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

No it's not getting hot.. But does the other regulator 5>3.3v feeding the 3.3v to this one? If so there is a breakdown somewhere in that line unless it's being pulled down on the 1.7V line? Is that likely?

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

you could lift it off of the board and see if your 3.3v comes back up.

That was my ? basically, so lift the 3.3V>1.7 regulator and see if input comes up to 3.3v?


Lifted input leg of the 3.3V>1.7 regulator but input voltage remains at 2.5V..

[attainteddragon]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

so now start working your way back to the supply voltage. with a good working board it should be easier to do.

post a high res pic of the area if you want more help, though i can't view it for a bit. dam teenager ate all of the data and doesn't refresh for 5 days. :'(

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

Here's pics.. I'll start looking at it tomorrow. If anyone can look for tips please and thanks

[budm]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

I suspect that the output of 3.3V regulator is bad which it feeds the input of the 1.8V regulator IC.

[kevinm34232]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

I have 5v in and 3.3v out of that regulator.

[budm]

Re: Samsung LN52A650A1FXZA dead, standby LED just flashes repeatedly

I have 5v in and 3.3v out of that regulator.

But some how it shows 2.5V at the input if the 1.8V regulator per your post:
'Lifted input leg of the 3.3V>1.7 regulator but input voltage remains at 2.5V..'
If you check the resistance between the 3.3V REG Output pin and the input pin of the 1.8V regulator, does it show < 1 Ohms?