Older Sanyo DP50747 VE Voltage High

[MagicSmoke]

Working on an old Sanyo 50" that has Samsung innards. Backstory.. saved from dumpster years ago, partial recap on SMPS, Replaced one of two small caps on X-main, set worked great for about 3 years.

Then recently it started to take a few minutes from power on to display a pic and sound, worked like that for about 3 months, then Smps would click once and then nothing, it will not shut itself off but nothing happens.

So pulled PS replaced all the caps, even the large mains. PS works and has all stable rated voltages present when switched on. TV has sound (static) when on but no screen charging happens.

VA and VS are stable and at specified volts, BUT VE voltage on X-main is above rating by 37 volts (supposed to be 94v but is 131v) and will not adjust down. Nothing on X board looks burnt or cracked. All fuses on X board are good. Pulled the other small cap and it tests within spec.

Tried removing main board to test for color patterns but still no luck, logic board flashing fast from VE being high I guess. VS and VSCan on Y main are present and correct. No componets look burnt on Y or buffer boards.

I have another logic board exact P/N from a Phillips 50" that I tried but same symptom VE high.

Am I correct in thinking that the problem is on the X-main since it generates the VE from the VS voltage? Or has the panel gone bad? Picture had been great til above happened. Thanks.

[MagicSmoke]

Re: Older Sanyo DP50747 VE Voltage High

Did some more testing, found if I disconnect the panel ribbons to X-main and power on VE is right on rated volts 93v. But if the ribbons are connected when powered on then it jumps to 137 and still no screen lighting.

Has the panel gone bad?

[Biruslapio]

Re: Older Sanyo DP50747 VE Voltage High

Does the TV produces an image without X-Main? It is capable of, but some models refuse to turn on without everything connected.

You can try in three different ways, by disconnecting it from the panel, VS cable from Y-SUS or the logic board.

And what if you disconnect the Y-buffers to panel but leave X-Main fully connected?

[MagicSmoke]

Re: Older Sanyo DP50747 VE Voltage High

No image or screen charging with x Main disconnected.

I unhooked the LVDS cable to X and powered on, still no image but VE is now correct at 94 as is all other volts, VA,VScan, VS, 5 and 12 volts all good.

Even though the indicator led is flashing once per second, I am beginning to think that both of the logic boards I have are faulty.

[Biruslapio]

Re: Older Sanyo DP50747 VE Voltage High

So the problem only appears when the logic board fully enable the Y-SUS, because it will not work without everything connected.

X-main seems capable of producing VE without logic board.

Have you tried the 3 ways to isolate X-main from the TV? What about the panel to Y-buffers cables? By removing those cables it eliminates the chance of voltage leaking into X-main from Y-SUS in the case of maybe a defective panel.

I have almost no experience with old samsung plasma boards