Sylvania LC320SLX No Power-Dead

[selldoor]

Re: Sylvania LC320SLX No Power-Dead

You said I should be getting 135v is something wrong if Im getting around 165v which is what Im getting off of large cap?

No - nothing wrong -I think the earlier 135 may have been either a mis type or got the multiplier wrong and used 1.14.

120 VAC rectified is 120* 1.41 = 160.2 VDC

Your mains is likely less than 120 VAC so 165VDC is acceptable.

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

what your seeing @ that measurement @ this time of 165 volts DC is complete source voltage derived from your bridge rectifier network,once Q601 and its associated circuit start its operations you should see that 165 volt reduce down close to the 135 volt

[selldoor]

Re: Sylvania LC320SLX No Power-Dead

No - nothing wrong -..........
120 VAC rectified is 120* 1.41 = 160.2 VDC WRONG

Your mains is likely less than 120 VAC so 165VDC is acceptable.

Probably confused you even more - sorry

Should be 120*1.41 = 169.2VDC

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Ok going to replace the bad resistor and see what happens well let you know what happens..

[kevinm34232]

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

I have not tested all the diodes yet but I replaced the one bad resistor and at Q601 I have 163v at drain and 2.0v at gate. Does that give any indication?

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

I know this is first thing to check but I removed main filter cap which is a 470uF200wv, it measures 414uF, ESR 0.07. Is it bad?
I've checked all resistors and diodes on the "hot" side of the board now all seem good.

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

did you use the same dvm you measure voltage with to measure the Capacitor? again how accurate is it? The 470uf most likely is rated @ +/-10% so if your reading 414uf i would replace the cap,the voltages on Q601 should be suffient to startup set if nothing else bad.I think you said in a prior post that Q601 gate had 0.00 volts due to a open R614 you replaced and now you have 2volts

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

I have a Peak Atlas cap meter that I used to test it. That A33 voltage we were talking about I have 7.7v now, is that supposed to be 33v or 3.3v? Right on Q601 but I think I had 0v when the fuse blew so I'm not sure if I had voltage there before that.

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

OK so I will replace C605 (do you think this would be the cause of the TV not coming on, i.e. replace before continuing?)

And according to SM, that leaves Q601, Q602, and T601 to check?

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

yes your al33v should be al33 if your getting 7volts thats to low and will not work your al33 volts comes from diode D638 also your al3.3 comes from IC631 pin 2

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

no i don't think the C605 cap is keeping set from coming on,remember now since your on the secondary side of T601 for measurement make sure your using ground from secondary side like i post early i think it's pin 15

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

OK should I check Q602 and T601 first and how?

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

you can check Q602 for b-e short or e-c short also voltage from Q602 with using pin8 of T601 for ground as for t601 possible issue thats very low possibility now back over on secondary side @D638 source for al33v being thats low @7volt with set unplugged make sure you have no low resistance short from cathode which is band side of diode to pin 15 of T601

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

OK so here's what happens, with my meter on 200k I put black probe to pin 15 of T601 and red probe to band side of D638 and the readings on the meter just keep going up until hits 200 then 0L.

FYI I have 3.3v on pin2 of IC631.

As for Q602 I have 2.0v on collector pin 2, 0.2v on emitter pin 1.

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

D638 indicate no shorts now,using pin 15 ground of T601 go back to D638 cathode (band side) and reread your voltage there also since you have the 3.3volts on ic631 that now tells me things on primary side of T601 is working so when can forget now Q601,Q602 and associate circuit

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Hey Ron can look at page 37 of SM Block Diagram pin 2 of IC601 is 7.7v same as D638 also see a feedback circuit, any relevance?

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Same voltage reading using pin 15 and/or chassis and cathode/band side 7.7v.

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

IC601 voltages

Pin 1 - 6.6v
Pin 2 - 7.6v
Pin 3 - 0.6v
Pin 4 - 0.2v

Assume using ground from each side of IC?

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

ok something sucking up our voltage on cathode D638 we need to start eliminating things on that 33volt line thats killing our 33v
located R661 lift one side then read voltage again @ D638 see if come up

[budm]

Re: Sylvania LC320SLX No Power-Dead

Since the T601 transformer is used to generate more than one output voltages (multi output windings), are other output voltages OK beside the 33V supply?