Should I have 120VAC on both sides of this component?
Yes, I think so.
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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.
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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
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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
The diodes are not open? No cold joints? Try measuring the voltage drop across the diodes that feed that cap.
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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?
What meter do you have -- is it True RMS capable? If so, AC or DC range across them will work.
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Can you highlight that diode on the board somewhere?
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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.
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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?
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.
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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
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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
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