Sanyo DP42849 - No Power At All

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Nothing on the secondary side.

I've tried several times in case I'm doing something wrong . . .

[tom66]

Re: Sanyo DP42849 - No Power At All

Very odd, will try and think through this tomorrow and update. Bump if forgotten .

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Maybe I'm doing it wrong. I'm testing the two pins of IC602 that are connected to the primary side of the board with DCV 20.

[tom66]

Re: Sanyo DP42849 - No Power At All

That is correct. I have a few tests in mind, for now check what R904,R906 measure on 20kohms scale. (I'm sure you're tired of pulling that board in and out by now, sorry......)

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Naaa, it only takes a minute to do. If it'll get my TV working, I'll do whatever.

I'll check those now.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

R904: 2.00
r906: 12.05

[ridgerunner]

Re: Sanyo DP42849 - No Power At All

practice is good !,just unplug the tv ,and let the capacitors drain,you can play with the probes then.to see how you get on.still be carefull though as they still can rise.

the max on that filter cap should be around 172v when tv is powerd on and less with just plugged in.

you want to set your meter to DCV volts, ,think yours is 500v dc max?set it to that.

measure the large cap,black to stripe,red to the other pin and post back both readings,just watch the heatsinks ,(all the aluminium sheilds)as they will bite you if you touch them.and it does hurt!

that meter wont measure capacitance or esr ,if your doing this stuff a lot then you will need an esr meter,but we can still do a little test just to see if they are at fault in a bit.

I am getting 372 volts on mine with 148 on the AC line in. What would this high voltage be caused by?

[ridgerunner]

Re: Sanyo DP42849 - No Power At All

Correction. I am getting 169V DC on the cap with the power off, 320V DC power on, and 128V AC line in.

[Alastair E]

Re: Sanyo DP42849 - No Power At All

Prob the PFC....

[ridgerunner]

Re: Sanyo DP42849 - No Power At All

Correction. I am getting 128V AC line in, 169V DC on the cap with the power off and 320V DC on the cap with the power on. Too high? What would cause high voltage on this cap?

[Alastair E]

Re: Sanyo DP42849 - No Power At All

The PFC circuit....

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Bump.

[tom66]

Re: Sanyo DP42849 - No Power At All

I have been thinking about this for the past day or so and can't explain your zero reading on the secondary. Can you show me how you're testing?

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

I plug TV in, put meter on DCV 20, and touch leads as indicated in the picture. Then try it with power pressed.

[multimeter]

Re: Sanyo DP42849 - No Power At All

jeesh,forgot all about this thread,this one seems a pain in the arse dosent it?,i think tom is getting there in the right direction,i seem to remember on another set ive worked on with these damned optocouplers had me baffled,pc123's,i managed to test them with 2 analog meters in series to test the transistor side,outputting around 24v on the meter showed up a bad side on the opto,one or 2 of the opto's were for feedback,and was preventing the psu from powering up,but the led side of the opto was working,(reading one way only on diode test)confirmed good,the transistor in the opto cant be tested ,unless you use 2 meters in series,the voltage in a dmm was insufficiant to find a bad transistor in the opto,trying to explain the opto configuration was like this if you imagine the led side of the opto as an arrow they went like this there was 4 of them, ^ ^ and the other 2 were pointing down.V V.

might be worth checking them ,they dont have a high failiure rate,but i have come across one or two bad.

[multimeter]

Re: Sanyo DP42849 - No Power At All

Maybe I'm doing it wrong. I'm testing the two pins of IC602 that are connected to the primary side of the board with DCV 20.

just below the link marked j48 in that picture,there is a zener diode,is it me or is there a crack in that zener diode?,it looks to random to be a manufacture mark??

[lookimback]

Re: Sanyo DP42849 - No Power At All

I have the same TV. I spent 3 weeks before I figured out I had a shorted primary on the inverter transformer. I have 3 power supplies and 2 need transformers. I was going to rewrap them but I cracked the ferrites trying to get them apart. I think the second one I could have gotten apart, I put it in the oven for 45 minutes on 350. I should have had something better than needle nose pliers though.

Anyway, I figured out that there is a shutdown circuit. I think its part of IC301. Probably not the case with Nihon's but if the resistances on the big transformer are too low (in my case .3 ohms between pins 1-2, 4-2) it shuts down.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

just below the link marked j48 in that picture,there is a zener diode,is it me or is there a crack in that zener diode?,it looks to random to be a manufacture mark??

You mean this one (pictured below), multi? I test it with diode mode - got 750 one way and "1" the other.

Here's a picture of IC301, too.

[NihonNoir]

Re: Sanyo DP42849 - No Power At All

Should I retest IC602?

[tom66]

Re: Sanyo DP42849 - No Power At All

I wondered what had happened to this thread. My fault entirely for not following up on it. I'm nearly reaching the end of possibilities. I can't explain the results you are getting, unless the optocoupler is bad.