Advent PS-42D8 No Picture (Samsung Guts)

[Snorkasaurus]

Greetings!

I was given this television and was told that the screen went dark, but that sound continued to play. I have plugged in a media player of mine via composite but can't get any sound out of it. Unfortunately because the screen is not working I am unable to know if I have the correct input selected. When the TV is off I have a solid red LED on the front, which changes to blue when I turn it on via either the front buttons or the remote.

Thanks to some of the helpful posts here I was able to at least get started on this feller, but am hoping that someone might be able to help me along. Upon opening it I found four caps that were clearly popped (red circles in photo). The two brown ones at the top left were 200V/1200uF while the two black ones at the top right were 450V/330uF. After replacing them I was still getting no picture so I checked the voltages listed on the sticker found inside, with these results:

va: 79V expected, 79.3V measured
vsc: 78V expected, 78.7V measured
vs: 87V expected, 17.8V measured
ve: 107V expected, 106.3V measured
vset: 83V expected, 0.0V measured

I found Tom66's post about plasmas but got a little stuck since I am not actually sure if there is audio or not. My voltage readings seem to indicate to me that I have a messed up voltage regulator somewhere so I was reading retiredcaps' thread about testing voltage regulators which lead me to find a couple of KA7815's (marked pink in the photo). The board is marked as a Samsung B4K-50 (LJ44-00055A) Rev 2 - and I got these voltage readings from the KA7815's:

#1:
pin1 = 17.90
pin2 = -0.01
pin3 = 14.97
#2:
pin1 = 17.90
pin2 = -0.01
pin3 = 14.98

These seem okay to me based on my limited understanding of retiredcaps' post but I'm not confident that I am interpreting these results correctly. Perhaps someone might be able to help provide a push in the right direction? :-)

If there is any portion of the TV that someone would like a closeup photo of please just let me know.

HF,
S.

[Snorkasaurus]

Re: Advent PS-42D8 No Picture (Samsung Guts)

Anybody mind if I bump?

[freakaftr8]

Re: Advent PS-42D8 No Picture (Samsung Guts)

First those caps are bot popped. The plastic cover on the caps bubble up with heat. Im sure the caps are fine.

Unplyg the ysus. The board on the left.from the power supply. Do you get power now to vs and vset?

[freakaftr8]

Re: Advent PS-42D8 No Picture (Samsung Guts)

on those voltage regulators pin two will always be ground so if you're getting a reading of 0 that's normal in the ohms Range are you reading pin one and pin 3 with the red lead and the black lead on pin 2 (center) ? They should msasure in the kohms both directions. Are there any fuses blown on the power supply? How about the sustain boards. if you get voltage at the power supply now you can try to disconnect the two buffer boards coming off.that ysus going to the panel. disconnect the board from the ysus. Its not necessary to remove the connections from the panel. Then power up and see if you get voltage with the ysus connected to the power supply again but buffers disconnected from tbe ysus.

[Snorkasaurus]

Re: Advent PS-42D8 No Picture (Samsung Guts)

Hey freakaftr8, thanks for the reply... I had a chance to look at it tonight and unfortunately unplugging the ysus/ybuffs didn't change anything. However, I decided to try with the xsus unplugged and I got

va: 79V expected, 79.3V measured
vsc: 78V expected, 78.7V measured
vs: 87V expected, 72.6V measured
ve: 107V expected, 107.8V measured
vset: 83V expected, 78.9V measured

Which may not be perfect but is a significant improvement. From what I have seen around here ysus seems noticeably more likely to fail and of course I have to run against the grain. :-)

It sounds to me like replacing the xsus will get me headed the right direction but do you think there would be any point in checking the dozen or so caps on the xsus first? I've tried to read up on testing caps and realize that a real ESR meter is required, however a couple of things stand out at me. The first is that I can't see what makes some meters a lot more expensive than the ones that can be eBay'ed for $20 in some cases. Perhaps I am just being cheap, but is there anything they can't do that the more expensive models can? Really just an honest question, if they are technically inferior I don't have any issue shelling out the extra money.

Also, from what I have read it seems that testing caps is a bit of an art... that it isn't completely black & white, and that bad caps can test good while good ones can fail. Not that this happens all the time, just that testing caps isn't always 100% reliable. Is this your experience as well?

HF,
S.