Sylvania LC320SLX No Power-Dead

[kevinm34232]

I get no lights or anything when powered on, tested voltage good to filter cap, not sure where to go from here.

[multimeter]

Re: Sylvania LC320SLX No Power-Dead

what voltage are you getting at the main filter cap?,next step is to check your output voltages against there respective marking on the pcb,write down and post i.e

pin 1, 12v- actual = 12.6v

etc ,does anything light up on the tv front?,any led?,a screen flash?,

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

174v at main filter cap.

No nothing lights up no LED, no screen light at all, just DEAD.

This TV is a little different then the norm

[selldoor]

Re: Sylvania LC320SLX No Power-Dead

hi - have you read these threads.
As with one of them your pictures are not really clear enough for trouble shooting.

https://www.badcaps.net/forum/showth...light=Sylvania

https://www.badcaps.net/forum/showth...light=Sylvania

Check the screen panel is not cracked and look for shorted diodes.

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Panel is not cracked Im checking diodes now.

Well found some info on same set dead with problem being D639 (43-volt zener diode), not sure how to test it though.

[tom66]

Re: Sylvania LC320SLX No Power-Dead

Test forward and backward.

Good diode measures 400 - 700 one way, OL/"1" the other.

Bad diode measures zero or nearly zero both ways, or OL/"1" both ways.

These TVs are really cheaply made - using a poorly engineered self-oscillating power supply so lots of things can go wrong.

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

From SM:

Is the AL+33v line voltage normal?

Not sure where to check this but no voltage at D638.

C605 D601 D602 D603 D604, C638 D638 D639. Caps are good, diodes seem to test OK although thought Zener diodes tested differently.

Not tested Q601 Q602 T601 because not sure how.

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

to read the al33volt line see diagram attached if your voltage is mising one common issue on this chassis is for R618 to open make sure set unplugged desolder one end out of circuit and read on resistance scale for 390k reading see attached of resistor circled

[budm]

Re: Sylvania LC320SLX No Power-Dead

Per Ron diagram, do you also get any DC voltages on D646, D633, D640 (just move the red probe to the banded side of the diode)?

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Back it at tonight..

Bud, no voltages at those diodes.

So I pulled 1 leg of R618 and checked resistance. I get no reading (.0L). I'm guessing that means it's bad?

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Can I use any of these:
http://www.digikey.com/scripts/dksea...+1%2F4W+J+390k

Also what would be a good resistor for discharging large capacitors? Or is there another way?

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

yes OL would mean open,what scale setting did you have set on your dvm?

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

2k. Nothing on 200 either.

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

need be set on above 200k and those top 5 listing from digikey ok replacement

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Nothing on 200k, but at 2M .396

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

your resistor is ok then

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

going back to the diodes you checked for voltages also make sure none of those diodes are shorted use your diode scale on dvm to check

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

if no diodes are shorted ,then using pin 8 of T601 as ground read dc voltage @ Drain of Q601 should have 134 vols DC when set plug in if you do have the 134 v there then check for 5.3v on gate of Q601 those two voltages must be present to kick start Q601 into oscillation to get the power supply running

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

OK thanks will do

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Ok I have 4.6v at gate and 0v at drain using hot ground, so I guess I need to check diodes on primary side?