Sanyo DP42849 - No Power At All

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Well, I've emailed him and see if he'll take any less. I'd be surprised if it's gone - most people equate Sanyo with no-name brands, even though it used to be a quality Japanese brand before being sourced to China. We'll see.

Here's what I got:

Point 1: "1"
Point 2: 0.00

[tom66]

Re: Sanyo DP42849 - No Power At All

OK, can you see part number on Q303?

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

No picture, there is a chance that big inverter transformer is bad, (if no backlight) but you can swap them over, it's just a lot of work.

Are there any on-site tests that I can do that will give me a better idea of which board is the issue?

Let me see if I can find Q303.

[tom66]

Re: Sanyo DP42849 - No Power At All

Q303 right next to those points you were ohming out.

If the faulty TV has no backlight but makes sound, then it's likely the transformer.
If it has a backlight but no image, it's not the transformer.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Wow, that thing is tiny.

I can make out a 2, and then a T, and then what looks like another 2 turned once counter-clockwise.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

So would shining a flashlight into the screen be a good way of testing for an image without backlight?

[tom66]

Re: Sanyo DP42849 - No Power At All

So would shining a flashlight into the screen be a good way of testing for an image without backlight?

Yes.

[tom66]

Re: Sanyo DP42849 - No Power At All

Likely MMBT4403.

I traced out what I think the schematic for this area is, reverse engineered.

Try and follow Blue 1 and Blue 2, as indicated. They go off the edge of the image.

When U303_ON_OFF is pulled LOW, the main controller will start working.
PFC voltage is ALWAYS active, provided Main VCC is OK.

I suspect Main VCC is NOT OK.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

I'll give it a try. In the meantime, here are some better shots of that area.

[tom66]

Re: Sanyo DP42849 - No Power At All

I've traced some of those lines, I think one goes to J16 and other to IC203 or IC303.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Blue 1: Looks like it goes to IC303. Then through IC303 to J37.

Blue 2: To J16. Then Q602. Not sure if it stops there or keeps going.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

I've traced some of those lines, I think one goes to J16 and other to IC203 or IC303.

That's what I got too!

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Is there anything else I should try or test?

Thanks!

[tom66]

Re: Sanyo DP42849 - No Power At All

Plenty more; but I'll pass over to others for now for a good night, and will try and post tomorrow. Should this not happen please bump the post.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Bump.

[tom66]

Re: Sanyo DP42849 - No Power At All

Yep, thanks for that, completely forgot
Anyway, check voltage across C603 and ZD601.
Also, voltage from J16 to the -ve of small cap.
Also, voltage across primary side of IC302 and IC303 optocouplers.
(Board installed, same procedure with green light.)

We are closing in on the fault with any luck. It might be Q602 or the optocoupler which is bad.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Thanks. I'll work on this later and report back.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

C603 - 0.06
ZD601 - 0.12
J16 - .03; goes up to .06 when power button is pushed

I don't know how to test the ICs.

[tom66]

Re: Sanyo DP42849 - No Power At All

OK, looks like IC601 is not switching at all.
This is getting a bit tedious, but part # of IC601?

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

2A09303
5541

Not positive on that 2, but I'm not sure what else it could be.