Platinum (LG) plasma TV with no picture (blown Y-sus fuse, short on YPPD-J014C board)
Good day folks, basic problem with a Platinum (really an LG) plasma display that I've got on my bench (can't remember the exact model, sorry). I've put LG in brackets because all the boards inside are LG branded. The TV has no picture, but the sound is fine (that's what the client told me at least, since I didn't have the patience to lug this 100 kilo beast all the way up to where I've got the antenna lead). Opened it up and right away blown fuse on the Y-sustain board (located on the left of the TV, looking at it from the back with the cover removed). X-sustain (right side of TV) has both fuses intact, so I'm guessing it's fine. There are no other signs of damage (no bad caps or anything).
I started probing around with my meter and sure enough, there was a short between VSC and GND on the Y-sus. With a lot of time and effort I was able to pull out the large heatsink along with the component underneath it, the YPPD-J014C, which according to the interwebs is a "hybrid IC IPM"...not having worked with plasmas too often, I must admit I don't exactly know what it stands for. I mean I have a general idea of what it's doing, but not entirely sure. The fact remains that, after removing this thing, the short on the Y-sus itself went away, so I'm definitely on the right track. I then flipped the heatsink over and realized that the YPPD is actually a small board strapped to a heat spreader and the circuit is not too complicated - I was actually able to find it somewhere, which is more than can be said for other TVs. It turns out Q1, Q5 and Q7 on the YPPD are shorted (I can't believe those things are actual transistors - I thought they were just jumper wires). The short itself is between the pins labeled Chassis GND (CHGND) and "SUS_DN_OUT" on the Y-sus board. Some of those diodes on the YPPD might be shorted too, but I haven't checked too deep yet. My resolution is to replace those FETs with D-Pak ones (as shown in a tutorial that I found), but then I remembered that when a transistor fails, there's the possibility of current leaking into the control circuitry and damaging it and I really wouldn't want to go through all the trouble of installing new FETs only to discover that there's a fault somewhere else and the fuse blows again. Those small resistors don't look charred or burned, and since they're in series with the gate of the transistors, I'd go as far as calling the rest of the circuit fine. Remember, I first have to fiddle with the board to get the D-Pak FETs to fit, then solder the assembly back on the Y-sus, try it out on the TV and then remove it again should it fail - not a fun job to do ! Have you guys encountered this issue ? More specifically, this YPPD board with the same symptom. Should I just look for a new assembly entirely (not too easy to find where I live and probably not very cheap either) ? Could there be a fault somewhere else that caused the damage in the first place ? Cheers.
I started probing around with my meter and sure enough, there was a short between VSC and GND on the Y-sus. With a lot of time and effort I was able to pull out the large heatsink along with the component underneath it, the YPPD-J014C, which according to the interwebs is a "hybrid IC IPM"...not having worked with plasmas too often, I must admit I don't exactly know what it stands for. I mean I have a general idea of what it's doing, but not entirely sure. The fact remains that, after removing this thing, the short on the Y-sus itself went away, so I'm definitely on the right track. I then flipped the heatsink over and realized that the YPPD is actually a small board strapped to a heat spreader and the circuit is not too complicated - I was actually able to find it somewhere, which is more than can be said for other TVs. It turns out Q1, Q5 and Q7 on the YPPD are shorted (I can't believe those things are actual transistors - I thought they were just jumper wires). The short itself is between the pins labeled Chassis GND (CHGND) and "SUS_DN_OUT" on the Y-sus board. Some of those diodes on the YPPD might be shorted too, but I haven't checked too deep yet. My resolution is to replace those FETs with D-Pak ones (as shown in a tutorial that I found), but then I remembered that when a transistor fails, there's the possibility of current leaking into the control circuitry and damaging it and I really wouldn't want to go through all the trouble of installing new FETs only to discover that there's a fault somewhere else and the fuse blows again. Those small resistors don't look charred or burned, and since they're in series with the gate of the transistors, I'd go as far as calling the rest of the circuit fine. Remember, I first have to fiddle with the board to get the D-Pak FETs to fit, then solder the assembly back on the Y-sus, try it out on the TV and then remove it again should it fail - not a fun job to do ! Have you guys encountered this issue ? More specifically, this YPPD board with the same symptom. Should I just look for a new assembly entirely (not too easy to find where I live and probably not very cheap either) ? Could there be a fault somewhere else that caused the damage in the first place ? Cheers.
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