Hello all! Just when I finally got done with my last tough job, another one pops up. I didn't want to have to come begging for help, but I caved in; this TV hates me.
Symptom: No picture, sound okay.
Found FS104 open on YSUS (located below the heatsinks near center of board), which is on the 18v line, so I replaced the YSUS and I had the same symptom. VS and VA were fine if I recall. I checked the fuse again and it was open. I had neglected to check it BEFORE putting in the board, so I didn't know if I had received a bad board. I ordered another and it came with a good fuse in it, but when I installed the board, still had same symptom. The fuse didn't blow, but I had unplugged the TV pretty quickly.
So....I rechecked the VS and VA...it was correct. I took out the Z-SUS (I had already resoldered) the coils earlier and double checked my soldering (good) and tried to find bad fets; couldn't find any, but didn't check systematically because I really doubted I would have VS and VA if that was the case AND the fuses on the ZSUS were good. I redid the logic test pattern thing to see if that was the issue, but no go. Then, I thought I would check the fuse again on the YSUS (FS104) and found it had OPENED AGAIN. The I realized that the first YSUS I got likely had failed within a couple of minutes and so had this second board. Great.
I pulled the buffers and tested them (wishing I had tested them before replacing the YSUS...I know, I know, I should have) and even after testing over and over again and very slowly and meticulously, I can't find any shorts.
Then I clipped in another fuse (it's a 2amp pico) and tested to see what the voltage is doing; it stays at 18v, but when testing the voltage drawing through it, I found it to be rising within seconds to .5 volts, at which point it opens the fuse. I check most of the fets on the YSUS, but found none shorted; it's difficult with the thermal pad that is stuck on, covering the pins. I suppose I could test on the top side if someone thinks it's necessary.
Then, I did various things with ANOTHER fuse clipped in to try to pinpoint the problem:
Of course I left both buffers out and tried to see if the fuse would not blow or if it would not draw too much voltage (I know current is the operative here, but I was extrapolating from the DC voltage draw), but it still did.
I tried disconnecting the logic from the YSUS, but that causes immediate shutdown.
I tried disconnecting the power to the ZSUS, but that doesn't stop it, either.
I don't know anymore. I'm at the point of replacing the buffers (even though can't find a short with them) and the logic and changing the YSUS a third time, but hope that someone can help.
Thanks in advance!
Symptom: No picture, sound okay.
Found FS104 open on YSUS (located below the heatsinks near center of board), which is on the 18v line, so I replaced the YSUS and I had the same symptom. VS and VA were fine if I recall. I checked the fuse again and it was open. I had neglected to check it BEFORE putting in the board, so I didn't know if I had received a bad board. I ordered another and it came with a good fuse in it, but when I installed the board, still had same symptom. The fuse didn't blow, but I had unplugged the TV pretty quickly.
So....I rechecked the VS and VA...it was correct. I took out the Z-SUS (I had already resoldered) the coils earlier and double checked my soldering (good) and tried to find bad fets; couldn't find any, but didn't check systematically because I really doubted I would have VS and VA if that was the case AND the fuses on the ZSUS were good. I redid the logic test pattern thing to see if that was the issue, but no go. Then, I thought I would check the fuse again on the YSUS (FS104) and found it had OPENED AGAIN. The I realized that the first YSUS I got likely had failed within a couple of minutes and so had this second board. Great.
I pulled the buffers and tested them (wishing I had tested them before replacing the YSUS...I know, I know, I should have) and even after testing over and over again and very slowly and meticulously, I can't find any shorts.
Then I clipped in another fuse (it's a 2amp pico) and tested to see what the voltage is doing; it stays at 18v, but when testing the voltage drawing through it, I found it to be rising within seconds to .5 volts, at which point it opens the fuse. I check most of the fets on the YSUS, but found none shorted; it's difficult with the thermal pad that is stuck on, covering the pins. I suppose I could test on the top side if someone thinks it's necessary.
Then, I did various things with ANOTHER fuse clipped in to try to pinpoint the problem:
Of course I left both buffers out and tried to see if the fuse would not blow or if it would not draw too much voltage (I know current is the operative here, but I was extrapolating from the DC voltage draw), but it still did.
I tried disconnecting the logic from the YSUS, but that causes immediate shutdown.
I tried disconnecting the power to the ZSUS, but that doesn't stop it, either.
I don't know anymore. I'm at the point of replacing the buffers (even though can't find a short with them) and the logic and changing the YSUS a third time, but hope that someone can help.
Thanks in advance!
Attached Files
Comment