Sylvania LC320SLX No Power-Dead

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

give me reading both ways on diode scale of your meter for D641,D642 then want reading from cathode of both diodes to ground, then voltage of both diodes to ground D642 is the source supply for your al13v line wanting to see if that line is also low like the al33v also you did say back few post ago that IC631 pin 2 had your al3.3 so we know thats correct

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

I lifted R235 and still have 8v at D638.

So by lifting cathode leg of D638 like Ron told me to do last night, shouldn't that isolate that AL33v circuit and I should have 33v on that lifted leg or am I wrong?

Just did it again, results are only 9-10v at D638 (using chassis as ground), but using pin 15 of T601 I get 6v. I believe when it wasn't lifted voltage was the same either way.

[budm]

Re: Sylvania LC320SLX No Power-Dead

Since D38 is the one that generates the 33V power supply, that 33v is fed into Q210 Collector through 330 Ohms resistor R235, in the worst case if the output on the Emitter ishsorted to ground, the most current draw will be onlt 100mA which is small and should not be bad enough to load down the 33V line that much at all.
So how much voltage do you get when the Collector of Q210 is lift (or lift R235)?

[kevinm34232]

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)?

Oh sorry Bud missed that one.

I had D638 and Q210 lifted from last night:

D646 = 5.7v
D633 = 4.5v
D640 = No diode there

When I reconnected D638 and Q210:
D646 = 2.0v
D633 = 1.5v

[budm]

Re: Sylvania LC320SLX No Power-Dead

What DC do you get at post 9 that asked earlier. If you do not have correct voltages at those points, that will explain why the 33V is bad also.

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Desoldered Q210 collector leg no difference at D638

What's source of A33v?

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

OK done and interesting. 6.7v with red on D638 cathode lifted leg while when reading with black probe on pin 15, and 10.7v when black probe put to chassis instead of pin 15.

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

lets lift cathode of D638 hang positive probe to cathode and read the voltage from the diode it might be slightly higher if the voltages come up NOTE!! maker sure the cathode is lifted all way up off board

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

D39 was in range of what you posted earlier one way, and 0L. the other way. If you need me to get exact reading let me know. I will try isolating Q210 next, should I just start checking all the diodes and resistors aswell or any in particular? I really appreciate all the help this is great learning...

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

you can desolder the collector of Q210 also when you checked D639 out of cicuit what was your reading on the Diode? check with diode scale on meter forward and reverse polarity?

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

The voltages are all off especially the ones supposed to be 30+v, should we somehow isolate Q210?

[RON_CET]

Re: Sylvania LC320SLX No Power-Dead

ok check these area circled in green also Q210 is connected back to the 33volt supply but if you noticed Q210 also supplies the 24 volt line so if something loading the 24 v line could also affect the 33v line

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Lifted R661, 7.9v at D638

[kevinm34232]

Re: Sylvania LC320SLX No Power-Dead

Ok will do just lifted and checked C638 D638 D639 diodes are good capacitance on C638 is a little low similar to C605.

[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?

[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

[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?

[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

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?

[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