Sanyo DP42740 no power

[Agent24]

Re: Sanyo DP42740 no power

Did you compare the two PSUs to be sure they were compatible - at least had the same rails on the same pins etc?

[triplefour]

Re: Sanyo DP42740 no power

yea they r exactly the same

[Agent24]

Re: Sanyo DP42740 no power

I wonder if you disturbed some loose connection when replacing the PSU?

[triplefour]

Re: Sanyo DP42740 no power

i dunno what could be loose. i will have to wait to tomorrow to look at the tv again

[triplefour]

Re: Sanyo DP42740 no power

ok 2 days went by and im looking at the tv again. i left it with the original psu installed. now it powers up and backlight comes on just fine but i just get a blank backlit screen like the TCON is out or the motherboard is not giving the signal. why has the problem jumped from the PSU to the main board now???

[budm]

Re: Sanyo DP42740 no power

Oops, wrong info.

[triplefour]

Re: Sanyo DP42740 no power

update: i had to upload this on youtube cause i cant quite describe what im seeing here now

https://www.youtube.com/watch?v=hwo4...ature=youtu.be

description:"first the tv worked normal for a whole day before shutting down. then it worked normal for an hour or two. then an hour. then not at all. then we let it rest a few days and it worked for a couple hours again and then shut down. so i figured we had a power supply problem and ordered the replacement PSU. before installing the replacement PSU, i powered up the tv one last time just to check, and everything worked fine. probly woulda stayed on for an hour again, i dont know. so i decided to change the PSU anyway. the replacement PSU would not even power the backlights. it would just click on with the green light and then off in 1 second.
so i put the orginal back in, and it did the exact same thing! so i let it rest for a few days again. when i came back to it, it would now power on but i was just getting a blank backlit screen. i could tell everything else was working fine because i was able to change the input to av1 and hear my gamecube, just not see it. so i followed the troubleshooting steps in the service manual, unplugging certain boards and checking certain pins for shorts. didnt find any shorts. then i got to this step:
"not shorted = Power ON TV, and check TPVSUS (SN2, pin #1) for 191V before shutdown
If no output, = SMPS N/G
If 191V OK is before shutdown, SN Bd. may be defective (can not be sure)"
with some of the connectors unplugged, the tv goes into a shutdown mode after 1 seconds but apparently you're supposed to see voltage on that pin for a second. but i dont see any.
so that doesnt look good, i think to myself. but then i wonder how can i be seeing a backlight then if there is no voltage on that pin?
so i plug everything back in to see what the voltage would be then, and if the tv would still come on. now i measure that same pin and get 200v and well...this is what im seeing on the screen. in some scenes it looks alright but just a bit grainy and in other scenes it seems like its displaying 2 images at once. what's going on here?"

[triplefour]

Re: Sanyo DP42740 no power

input, anyone please?

[triplefour]

Re: Sanyo DP42740 no power

must be the holidayze :/

[triplefour]

Re: Sanyo DP42740 no power

ugh...either youtube took my video down for some reason, or it was never up there to begin with...or i copied the wrong link...
either way heres the video
https://www.youtube.com/watch?v=hwo4OtgHZIc
and can someone please please advise me what this is?
im not too familiar with plasma TV's... and i havent seen this kind of image distortion before.

[triplefour]

Re: Sanyo DP42740 no power

does no one have any idea what im looking at here?

[Agent24]

Re: Sanyo DP42740 no power

Maybe the voltage is supposed to be 191v and at 200v is too high?

[triplefour]

Re: Sanyo DP42740 no power

yeah maybe but i have no idea what im looking at here. i barely know what im looking at with regular LCD's but im totally lost on the plasmas...plus its heavy and hard to work with. its just been sitting collecting dust for months now

[Agent24]

Re: Sanyo DP42740 no power

I don't know much about plasmas either. Never worked on one, only CRT and LCD so far. Hopefully some of the other guys can help you. Only thing I can suggest is reading threads on here, and looking at repair guides\videos and plasma set operation theory. It probably won't help you fix it, but it should help you learn something so that at least you know where you are and know the basics.

[triplefour]

Re: Sanyo DP42740 no power

thats great advice. sadly when i first joined here i had a lot of time, and did quite a bit of learning. but now since i know enough to be dangerous, it seems like i dont have the time to learn more! too busy fixing the TV's that dont put up as much of a fight! ...which i cant really complain about since i AM fixing them and making money now. except that im not really progressing anymore in my education.i will get back on it soon enough though...gotta pay them bills first! ...and buy a hot air/reflow station...and fix up that oscilloscope i scored... and... and...

[dstafursky]

Re: Sanyo DP42740 no power

resistance between 1 and 2 is 0.5ohms
when i put my meter in diode mode, i get 620 when i have the black probe on the side with the line, and 1 with the probes reversed.
when in resistance mode i get 35kohms with black on line and 55kohms with probes reversed.
the numbers on the IC are
TB5AH
6754MR

the DC voltage across the legs on cap rj15 is fluctuating ...as low as 6v and as high as 20v

thank you!

My voltage is zero...any ideas?