Sylvania LC320SLX No Power-Dead

[Mr Bill]

Re: Sylvania LC320SLX No Power-Dead

This was the diode that was shorted on my last sylvania that was completly dead. I never lifted any of the diodes. I checked them in circuit and if it read 000 then i removed to verify.

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Yes Ron correct everything was dead just was wondering.

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

I checked all diodes and resistors on the primary side, it's a big board and wasn't sure if it was practical to lift every resistor and diode on the secondary side without being instructed.. This is my board:
http://www.shopjimmy.com/sylvania-a9...unit-board.htm

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

those 3 resistors in that link are in the power supply startup for the backlight inverter,if those were giving you the problem of protect3 shutdown which is monitored @ pin3 of connector cn1001 first thing you would notice would be the power led on front of set would first go to red stanby then after you hit power it would go green and the protect3 line would go to 3.3 volts once the protect3 line goes to 0 volts from a inverter power supply issue then set would shutdown,from what i gathered you had no power at all to set not even a stanby led indication?

[Mr Bill]

Re: Sylvania LC320SLX No Power-Dead

I believe i read a post a while back that if one inverter transformer was bad it would shut the tv down. But, the tv would start to turn on (led would flash). You have no led at all. You did check all the diodes right? I'm only asking because it was mentioned very early in this thread but i don't see whether you confirmed this. The few sylvania's and emersons i've repaired all have had 1 bad diode. The one slyvaina LC420SS8 had no standby led. It was a shorted diode.

What is the board number on your power supply. I have a 32" emerson power supply in the basement.

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Question I see some voltage protect circuits in the SM is there any chance that the problem is elsewhere and shutting down the voltages we are looking for? I just googled the model # and came up with this:
http://www.fixya.com/support/t102899...vania_lc320slx

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

it does get it's Ac input from pin 11 T601 but if you lift cathode side of D638 you should see the 33 volt dc come up on the cathode,D639 would not prevent the 33 volts unless it was leaky or shorted and he did say D639 was good,be same thing if we had cold solder joint on the pad but at the leg we had the 33volts

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Sorry Bud as Im not educated enough in the function and how all of the components work together, I'm just trying to keep up with what you guys ask and follow instructions. Ideally for my own knowledge I'd love to have the same model working TV sitting next to this one to be able to compare readings to give you. However that said I appreciate any insight. I believe C638 tested good and D639 aswell on my DMM diode setting.

[budm]

Re: Sylvania LC320SLX No Power-Dead

If you look at the diagram, D638 is the rectifier (It gets its AC from transformer pin 11) that feeds filter cap C638 and the clamping Zener Diode D639. If you lift the leg D638 then for sure you will not have the 33V. I would look real close at that Zener D639, and that filter cap.
I do not understand why you expect to see 33v when the D638 is not in place.
Unless I am missing something.

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Yes thank you all for the help on this one I agree. Hate to give up but yes learned a lot. Have 3 or 4 more sitting here waiting anyways!

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Ok.. so since the 33v didn't come up when we lifted D638 any guesses? I'd be happy to keep going just don't wanna waste everyone's time for a crappy TV, Id have to order some parts first of course

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

look on the positive side you have learned a lot of troubleshooting techniques and that complete board is also very inexpensive if your wanting to just replace the board

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

kevin in theory by lifting the leg of D638 if there was something loading down that line our 33v should have come back up on just the cathode leg of diode we lifted,now from the rest of you standby voltages like the al13v thats low course now that the 2 pins were touch over on Q601 that transistor could be bad now

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

So can you help me understand what I should or could be looking for on my own? Does it seem to be a short on the secondary side, etc? Earlier I asked if lifting cahtode leg of D638 would isolate that AL33v circuit from D638 which is the source, is that true? Why are my other voltages low aswell like Q601?

Ughh I was just checking Q601 and touched 2 pins now I don't have the 163v there. This TV was almost free, it was all about trying to troubleshoot the problem. Should we just move on to the next one?

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Yes it seems connection is good to both spots using ohmeter 0.00. How about the buzzing noise is that the cap discharging?

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

ok lets address the possible foil issue @ R604 determine what end is issue look at diagram just make sure the top end of R604 reads to pin3 of T601 and bottom end of R604 connects to R605 top end

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Yes I replaced both of them and I have .383 on the meter for both set on 2M.

Another observation: The big main cap held that charge for a long time in the beginning, I even used the resistor you recommended and it took forever to discharge. Now when I put my meter on it after unplugging charge drops quickly on its own, I also hear a little buzzing from somewhere.
And the solder pad on R604 seems to be broken it doesn't form a complete circle although it seems to be partially there.

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

just seen your edit on last post about Q209 yes you could have open R247 or R227 or both or damaged Q209

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

ok back over on primary side where you replaced the R604 you did replace with same value 390k? also i don't see any where you also checked R618 should also be 390k go back check R618 but make sure you discharge the big cap first

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Ok I lifted leg for each diode to test:

D642 - .0L and 0.223
D641 - .0L and 0.224

Then resoldered checked cathode legs to ground, 0.L on both
Both diodes 3.3v

As a side note I was going thru the flow charts today trying to check other voltages came to Q209 and I actually had 23v there then I think I touched 2 pins together I saw a little spark now it's around 5v, did I burn something up?