Sanyo DP42849 - No Power At All

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

If I'd just done black to chassis like yous told me to, we would've been fine. Le sigh.

I get 4.99 on STB5V, and 4.99 on pin 12 of the large connector.
0 on all other pins.

[tom66]

Re: Sanyo DP42849 - No Power At All

Check pin 1 (looking from main board end; could correspond to different pin on power board), does this go up to >2V as you press the power button (i.e. TV in standby, press button and note any changes.)

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

On main board, Pin 1 is on the bottom. Not sure what it is on power board, if that's what you mean?

So the bottom pin on the power board goes from 0 to 4.99 when I press the power button. Then goes back down.

[tom66]

Re: Sanyo DP42849 - No Power At All

I'm about to go to bed but this means you have an additional fault on the power board. So that would have to be located and fixed.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Okay, I'll try to test stuff. I did try testing some resistors, but I never got any consistent results. A few are "1", others give me readings. Not sure how to work with those quite yet.

Have a good night.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Here's what I've got from some of the resistors on the board.

R1: 1
R2: 1
R3: 1
R4: 1

R843: 0.2
R905: 2.3
R322: 0.3
R255: 33.9
R256: 33.8

R901: 1
R900: 0.3
R603: 0.3
R604: 0.5
R331: 32.8
R332: 32.8

R132A: 156.5
R132B: 156.5
R132C: 156.6

I followed a video and tested BD1, Q601, Q302, and Q301. They seemed to be good - I didn't get anything different from this video

I did desolder one leg of R1 to test again - same result. Maybe R1-R4 are supposed to read the way they do.

[tom66]

Re: Sanyo DP42849 - No Power At All

So, did we find out if that big cap voltage increases to about 390V when power button pressed?

[selldoor]

Re: Sanyo DP42849 - No Power At All

where you have 1 is that one ohm or is it overscale - try moving the scale to the highest
ohms and test again.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

So, did we find out if that big cap voltage increases to about 390V when power button pressed?

Yes, a few pages back.

Tested main cap. 165 when TV is plugged in. It does not change when I press power button.

Same TV, similar issue here. There's no standby light on this set apparently.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

where you have 1 is that one ohm or is it overscale - try moving the scale to the highest
ohms and test again.

Well most of the resistors have their rating written on them and I assumed I could go by those numbers. In any case, still a 1 when using 200k on meter.

[tom66]

Re: Sanyo DP42849 - No Power At All

OK, so, next step is to get part number for this chip.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

1606b
penv

[tom66]

Re: Sanyo DP42849 - No Power At All

https://cdn.badcaps-static.com/pdfs/...a4df8cb40c.pdf

See if you can trace pin 8, Vcc, to a capacitor on the board, or to somewhere else, then test voltage across said device.

Or, you can try soldering a wire to pin 8, and check voltage directly on there, using the negative of the 450V capacitor as ground for your black probe. (You are testing primary side, which is isolated from the secondary, grounded side.)

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

So I'm seeing pin 8 as the one with IC801 next to it. It looks like it goes across J38, and from there I can't quite tell which way it goes.

Here are some pictures.

[tom66]

Re: Sanyo DP42849 - No Power At All

You could try testing voltage at J38 as positive point, and big cap negative as negative point, as before.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

So I would put my black probe on the negative pin of the large cap, and then touch the J38 wire on the front of the board with my red probe?

[tom66]

Re: Sanyo DP42849 - No Power At All

Yes.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

And this is checking to see if current is getting this far into the circuit?

I'll try it now.

[tom66]

Re: Sanyo DP42849 - No Power At All

This is checking if PFC controller and main IC have good Vcc. If they do, then they are both defective. From repair progress so far, it is looking like a power surge damaged something, though it's also possible damage was caused by the standby IC failing. I've had a set which blew the main power controller (similar in function to the standby controller); the resulting surge which was imposed on the Vcc line killed a few other parts along the line. Luckily, I had full schematics, so repair wasn't too hard, just tracing where voltages were disappearing, etc.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

I kind of understand that.

I just realized that the two screws on the power board that tested good for ground have the labels GP1 and GP2 next to them. Wish I'd seen that a week ago :/

So when I'm taking this board out and putting it back in - do I have to screw all the screws back in, or can I just do the 2 ground screws?