Viore PD50VH80 50" Plasma`

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

Regarding the transistors in post #6, is this a problem?

[tom66]

Re: Viore PD50VH80 50" Plasma`

Should I have 120VAC on both sides of this component?

Yes, I think so.

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

OK trying to trace this to the best of my ability..

Tom is the spot with the ? where the 2nd relay would give the bridge the HOT side 120VAC?

I have the 120VAC at the 2 spots noted, where it hits those 2 diodes. Is this where it's going to the standby section?

So is the AC sectioin fine then?

[tom66]

Re: Viore PD50VH80 50" Plasma`

I don't have a schematic of the exact same board but I have one from a different model, same generation. You should be able to understand how the input circuit works -- more or less the same.

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

Thanks for that..

What is the TH relay for? Neither one is clicking on, but I do have 120VAC across pins 1 and 2 of RL802S, but not RL801S.

Which relay circuit do I need to focus on?

[tom66]

Re: Viore PD50VH80 50" Plasma`

The TH relay bypasses the NTC once the power supply has started, this improves efficiency. The TV can work if this relay does not energise but it can lead to picture issues and overheated NTCs.

The ON/OFF relay turns the main power on to the PFC circuit which boosts the supply to 400V. The standby should still work without this relay functioning.

Note the 22uF/450V should have 160V in standby (US) and around 390V in operation, as it gets an extra feed in from the PFC circuit. If you don't have anything (160V) at that capacitor, then there's a fault on the input circuit somewhere or a blown fuse that's not obvious somehow.

Power on sequence (after power button pressed):
- ON/OFF relay toggled
- ~100ms delay
- TH relay triggered
- PS ON signal activated

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

I traced back from the + of the 22uF/450V cap and it only goes thru the fuse next to it, then thru 2 diodes (DB810 and DB811) back to the pins where I have 120VAC at the NTC. Diodes seem to be fine and there is 120VAC at the anode of DB810

But I only have about 1VDC across that cap.

[tom66]

Re: Viore PD50VH80 50" Plasma`

The diodes are not open? No cold joints? Try measuring the voltage drop across the diodes that feed that cap.

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

Does it matter which probe to where, or just either way across the dioide? DC or AC? Also, can I measure the V out of each diode and what would I use for ground?

[tom66]

Re: Viore PD50VH80 50" Plasma`

What meter do you have -- is it True RMS capable? If so, AC or DC range across them will work.

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

It's a cheapie meter. Set on AC I get a reading of around 7V across the first diode, about 0.5V across the second one.

[tom66]

Re: Viore PD50VH80 50" Plasma`

Can you highlight that diode on the board somewhere?

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

Here's from the bottom I will get from the top now, which diode are you looking at?

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

From top../

[tom66]

Re: Viore PD50VH80 50" Plasma`

Well, it's just a 1N4007. You could try replacing it (radioshack sell them) along with the others near it -- just leave the diode DB801 near the transformer alone.

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

You're talking about the one next to the cap? What should I expect to see as the 120VAC goes into the first diode into the 2nd one, it should be coming out at 160VDC?

[tom66]

Re: Viore PD50VH80 50" Plasma`

You should have 160V across the cap, but the layout of the diodes is really unclear I'm not sure what they each do. I wish I could get the exact schematic.

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

I have a UF4007GP-TP will that work for the 1N4007?

[tom66]

Re: Viore PD50VH80 50" Plasma`

That will be fine it is the ultra fast variant of the 1N4007 and would in fact be suitable for DB801 too, though I don't think you need to replace that.
If you give up, the board is about $50.
http://www.shopjimmy.com/samsung-lj4...upply-unit.htm

[kevinm34232]

Re: Viore PD50VH80 50" Plasma`

Ya I got a offer in on one on ebay now for $30. I hate to give up on it tho, Im gonna try replacing that diode, perhaps lifting the diode next to it that also goes to the fuse and then goes somewhere else.

Nah didn't work.. There is a 6 pin ICB801S (ICE3BR2565JF) close to this cap

http://www.alldatasheet.com/datashee...3BR2565JF.html

Could you look at this I think it produces the standby?

Checking the from the cap ground, it showing a short to pin 2 (current sense). Is that normal?

Edit: There is 0VDC to the VCC pin, that pin leads to a pin on the TB801S transformer.

I will try to search for a schematic