Sanyo DP42849 - No Power At All

[lookimback]

Re: Sanyo DP42849 - No Power At All

Red on 1 then black on 1.

IC 902 0.991 1.594
IC 201 1.025 1.969
IC 602 0.915. 1.066
IC 903 1.032. 0.861

I don't know if that helps any. I'm sure there are variances due to the differences in our meters.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Thanks for doing that. Could you elaborate on what you mean by "Red on 1 then black on 1"?

[lookimback]

Re: Sanyo DP42849 - No Power At All

First set of numbers was red probe on pin 1. Second set of numbers was reversed polarity.

Edit: I don't think I would put too much stock into the actual numbers though. The reading, I believe, is relative to the input voltage and our meters obviously have different output voltages in diode test.

[lookimback]

Re: Sanyo DP42849 - No Power At All

If you pull them from the board you can test them. An octocoupler is just an LED and a photo sensor. When the LED receives a current it lights up. The photo sensor reacts to the light and the resistance is reduced allowing current to flow. With the octocoupler out of the board you can connect a battery to pins 1 and 2 and, with your meter on ohms you should see low resistance. Then with the battery disconnected you should see high resistance. Not sure what voltage or polarity but I have the data sheet somewhere on my computer, I'll find it and post. I think a 1.5v battery. Nothing bigger.

Edit: That was pretty easy to find because I had uploaded it here when I was working on mine.

You can find a lot of other data sheets for ICs on this board in this thread if you need them.
https://www.badcaps.net/forum/showthread.php?t=33261

[lookimback]

Re: Sanyo DP42849 - No Power At All

Here's a pdf explaining how to use 2 meters to test octocouplers. Not sure if you have 2 meters but you can at least get a better understanding of how they work.

[budm]

Re: Sanyo DP42849 - No Power At All

Please note that as shown in the PDF, the Analog meter, the red probe has negative voltage output with ref to the Black probe, that is why it shows 20 Ohms as shown when Black probe is on Anode and Red probe is on Cathode, it is opposite from DMM.

[lookimback]

Re: Sanyo DP42849 - No Power At All

I hadn't even noticed the polarity was reversed. I have once again learned something new thanks to this forum.

[lookimback]

Re: Sanyo DP42849 - No Power At All

I don't think the octocoupler is your problem. As Tom said a few posts back, you should see about 1v in one direction (red on pin 1) and infinity in the other. He also stated that on your meter that would be 1200-1400. That's pretty much what you got. Tom is light years ahead of me on this stuff. I'm learning as I go just like you.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Thanks for the info!

Here are the final voltages with meter on DCV20:

First number is cold, second is hot.

IC903: 1.26 -- 16.58
IC602: 0 -------- 0
IC201: 4.97 -- -- 0
IC902: 1.05 ----- 0.88

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Bump.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Any ideas?

[tom66]

Re: Sanyo DP42849 - No Power At All

Sadly, I've run out of suggestions, sorry.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All



Is it for certain the power board?

[lookimback]

Re: Sanyo DP42849 - No Power At All

Sorry, I've been working so much lately that I haven't had time to get back to you.

Truthfully I can't exactly remember what the problem was and don't have time to read all the previous posts to catch up. Was this the one where it was no 5v stby?

I would suggest a little recap of the problem, symptoms, what you have tried already, etc.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

First had no standby, then replaced IC901, now have standby and green light when power button is pressed, but no picture, no sound, and no relay click.

So is it for sure the power board?

[lookimback]

Re: Sanyo DP42849 - No Power At All

Ok. So you are getting a turn on signal from the main. Have you checked the resistance on the big transformer?
On the primary side check between pins 1 and 2 then between 3 and 4. Secondary side between 5 and 6 then 9 and 10. I have had bad transformers in 2 out of 3 boards I've encountered so far.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Sorry, which part is the transformer?

[tw2005]

Re: Sanyo DP42849 - No Power At All

I don't want to get too involved since i don't have any LCD experience. I have flicked through the posts but at any stage since the stdby was restored has the main board been isolated and the PSU attempted to be forced on to see if it runs and all the volatages are there?

I'm guessing at what you're thinking, but there must be small possibility that the power fail cct on the main board similar to the Norcal video might be at play here.

Does this lock out after 3 successive attempts to cycle power and the LED go out like the video.

You're very determined i give you that spending this much time on the PSU.

[lookimback]

Re: Sanyo DP42849 - No Power At All

And make sure you do this with the power off and tv unplugged.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Does this lock out after 3 successive attempts to cycle power and the LED go out like the video.

Yes. No relay click, tho.

I don't know what that picture means.