Samsung 32" ln32b360c5d

[tom66]

Re: Samsung 32" ln32b360c5d

Can you post a picture of the bottom of the board? You can determine which windings go where by looking at the schematic, usually.

[Peale]

Re: Samsung 32" ln32b360c5d

All of the photos of the boards are here:

https://www.badcaps.net/forum/showpo...37&postcount=2

[tom66]

Re: Samsung 32" ln32b360c5d

OK, it is very rare for a transformer to fail, but here is how I expect the windings to appear shorted.

[Peale]

Re: Samsung 32" ln32b360c5d

Either I'm doing it wrong, or it's very, very shorted. Every one of those points appears shorted. But, wouldn't that not allow the TV to operate, at all?

I'd been talking about the inverter transformers, above. Those I finally figured out, and they read: 1.073, 1.076, 1.043, .993

[tom66]

Re: Samsung 32" ln32b360c5d

Nope, it should be shorted.

An inductor (which is basically what a transformer tap is), should always appear shorted.

You need a ring tester to verify the transformer turns are not shorted. However, this is very rare with SMPS transformers.

[Peale]

Re: Samsung 32" ln32b360c5d

I understand now, I think. You were looking to see if any of them were open?

Okay, on to the next thing - now what?

[tom66]

Re: Samsung 32" ln32b360c5d

I missed most of this thread. Tell me, are 5.3V and 13V are stable on the PSU outputs?

If the Power ON/OFF line is changing, then this could be the main board shutting down the PFC, causing the problem.
http://www.tgohome.com/ServiceManual...g_BN44-00289A_[SCH].pdf

The +13V powers the inverter, so it must be stable.

[Peale]

Re: Samsung 32" ln32b360c5d

If I've metered correctly, 5.3V is stable, as is 13V. The DET_5V goes from 4.74V to nearly zero when it starts flashing on and off.

[Peale]

Re: Samsung 32" ln32b360c5d

Though 5.3 is reading closer to 5.24.

[tom66]

Re: Samsung 32" ln32b360c5d

OK, near each inverter transformer there should be some ceramic caps (coupling capacitors), C1803, CI808, CI817, CI825 which should all read open on 2000 ohms.

[Peale]

Re: Samsung 32" ln32b360c5d

Yes, this is accurate. All reading open. If I put the meter on 2M I get a reading, but not until then.

[tom66]

Re: Samsung 32" ln32b360c5d

So if DET_5V is dropping out, check if the output of the LM358, UI802, pin #1, is high. If so, it might indicate that the driver detect circuit is detecting a stuck output.

[Peale]

Re: Samsung 32" ln32b360c5d

If I've done it correctly (black lead to ground, red lead to pin 1) then I'm getting nearly nothing. There was a sudden spike up to ~3.2V, but then that was gone, too.

[tom66]

Re: Samsung 32" ln32b360c5d

Problem is, I do not know if DET_5V should be high or low. The only way to be sure would be to disable the error detection -- force it at 5V or 0V -- and see what happens. Do you want to try that?

[Peale]

Re: Samsung 32" ln32b360c5d

I'm assuming a possible risk would be blowing the board?

Run a jumper from the harness to that pin?

When it's at zero, which is where it starts, wouldn't that be...well...zero?

[tom66]

Re: Samsung 32" ln32b360c5d

I don't think there's a risk of blowing up anything on the board. The trouble is that you'll have to cut one of the wires on the harness going to the main board, which could be tricky.

[Peale]

Re: Samsung 32" ln32b360c5d

It would be easier to slice the trace, instead. Easier to repair, also.

[tom66]

Re: Samsung 32" ln32b360c5d

You could do that. Then use a 100~470 ohm resistor to pull it to 5.3V, see if the set turns on, if not, try GND, through 100~470 ohms.

[Peale]

Re: Samsung 32" ln32b360c5d

Okay, so...which trace should I cut, exactly?

At what points should I be connecting the resistor?

[tom66]

Re: Samsung 32" ln32b360c5d

Cut the trace leading to the DET5V pin.
Then connect DET5V (on the main board end) to 5V or GND using the resistor.