Sanyo DP42849 - No Power At All

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Bump.

[tom66]

Re: Sanyo DP42849 - No Power At All

Doh. It's a 1N4148 type part.
I will try to trace the circuit.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

If you need more pictures, just let me know. Thanks!

[tom66]

Re: Sanyo DP42849 - No Power At All

Pics are good now. Trying to understand circuit. Can you check on continuity or 2000 ohms from NEGATIVE lead of C905 to NEGATIVE of big 450V capacitor?

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

I get ~001.

[tom66]

Re: Sanyo DP42849 - No Power At All

OK, so that is grounded.
Can you see a part # on Q901?
When you test D903, and got ~600, which side was positive, which side was negative? Can you highlight those?

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

I'll try to read Q901.

[tom66]

Re: Sanyo DP42849 - No Power At All

The circuit is starting to make some sense... I think Q901 is a PNP transistor.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

I'm amazed that you can make anything out of this.

Hopefully I'm looking at the right Q901 - it looks like 2T with a another 2 turned clockwise.

[tom66]

Re: Sanyo DP42849 - No Power At All

Think that's a PMBT4403. I'll try to trace the schematic out soon. That transistor might be bad. Looks like this surge/failure did some pretty nasty damage but with very little marks left behind.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Thought I'd check to see if there's anything else needed while I'm snowed in with nothing better to do.

I tend to keep all of my high-end electronics plugged into surge protectors . . . I'm curious if doing so could prevent something like this, or are surge protectors just a waste of money?

[tom66]

Re: Sanyo DP42849 - No Power At All

Surge protectors do very little unfortunately. They can help in some cases, so are probably worth having, but in most cases they don't do enough.

[tom66]

Re: Sanyo DP42849 - No Power At All

Traced the circuit.

[tom66]

Re: Sanyo DP42849 - No Power At All

Please test voltage across primary side of IC602, in standby and powered on.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

That's pretty amazing, Tom.

Do you mean test the 2 pins that are on the hot side of the board? If so, how do I do that?

[tom66]

Re: Sanyo DP42849 - No Power At All

Yep - just check the voltage across them.
If the voltage goes from HIGH to LOW (figures will vary) the opto is working and that transistor is not, for some reason; if the voltage does not change, need to look at the opto and/or the circuit controlling it.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

So red lead on one pin and black lead on the other. Does it matter which is which?

Meter on DCV 20v?

[tom66]

Re: Sanyo DP42849 - No Power At All

DC20V. Orientation unimportant for now

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Got 0 for standby and power.

[tom66]

Re: Sanyo DP42849 - No Power At All

Hmm, what do you measure on the other side of the device? COLD side only?