This is my first attempt at a Plasma TV repair on a broken set that was donated to a good home. Inspection revealed 2 of 3 3300uF 10V (IIRC) Samwa Caps (Code U9A PET) blown on the PSU and a dead (Y-Sus O/p s/c to Vs & Gnd) Y-Sus IPM on the 6871QYH953A Y-Sus panel. I checked the 4 power diodes around it and they seemed OK but after replacement of the failed items (and a fuse) I'm still left with a non-working unit.
Having read-up on this forum about IPM failures I took the opportunity to fit a fan to the heat-sink and did the same to the Z-Sus panel - I'll wire them up when I get it all working. At this point after running the set for a few minutes and probing around the Z-Sus module is warm but not unduly so but the Y-Sus IPM seems cold and unheated by doing any work, the display is blank with no hint of any glow, I was able to see a waveform of ~200V amplitude on the "Waveform" test point on the Y-driver/buffer and I can see on the 'scope signs of what must be an OSD signal which would be "stepping" across the display if it were to be visible. As far as I can tell the supplies to the Y-Sus panel are now OK. I noted down various high voltage supplies around the set:
Va = 60.0, Vs = 188.1
and on this panel:
P102 = 119.5, P101 = 200.4, -Vy = 200.1
all of these and the floating 5 and 15 V supplies seem good and quite close (bearing in mind the apparent low "loading" on the lines) to the printed label. And Vz is 99.9 on the Z-Sus panel.
Now I've seen that others have had fun with boards like this but this leads to my main question: Has anyone been able to track down an actual schematic diagram for this (6871QYH953A) panel? I've been able to download a free "Service manual" for the LG branded receiver but - as seems to be the standard for these LG Plasma Display based units - it only gives the circuit diagram of the control/system panels not the PSU and driver ones.
I do have a SOT23 SMD transistor (Q16) that has been broken away from the PWB (it became "unstuck" and lost a leg) - I think I caught it whilst working on the Panel. It is the only one of it's type on that panel and it seems to be around the buffering of the control lines where they arrive at the PWB from the SysCon board, I can't tell what effect it would have and that is why I think the diagram would help me (and to identify a replacement).
Having read-up on this forum about IPM failures I took the opportunity to fit a fan to the heat-sink and did the same to the Z-Sus panel - I'll wire them up when I get it all working. At this point after running the set for a few minutes and probing around the Z-Sus module is warm but not unduly so but the Y-Sus IPM seems cold and unheated by doing any work, the display is blank with no hint of any glow, I was able to see a waveform of ~200V amplitude on the "Waveform" test point on the Y-driver/buffer and I can see on the 'scope signs of what must be an OSD signal which would be "stepping" across the display if it were to be visible. As far as I can tell the supplies to the Y-Sus panel are now OK. I noted down various high voltage supplies around the set:
Va = 60.0, Vs = 188.1
and on this panel:
P102 = 119.5, P101 = 200.4, -Vy = 200.1
all of these and the floating 5 and 15 V supplies seem good and quite close (bearing in mind the apparent low "loading" on the lines) to the printed label. And Vz is 99.9 on the Z-Sus panel.
Now I've seen that others have had fun with boards like this but this leads to my main question: Has anyone been able to track down an actual schematic diagram for this (6871QYH953A) panel? I've been able to download a free "Service manual" for the LG branded receiver but - as seems to be the standard for these LG Plasma Display based units - it only gives the circuit diagram of the control/system panels not the PSU and driver ones.
I do have a SOT23 SMD transistor (Q16) that has been broken away from the PWB (it became "unstuck" and lost a leg) - I think I caught it whilst working on the Panel. It is the only one of it's type on that panel and it seems to be around the buffering of the control lines where they arrive at the PWB from the SysCon board, I can't tell what effect it would have and that is why I think the diagram would help me (and to identify a replacement).
Unfortunately that didn't work!
) managed to get the thingy off the board. Being curious I saw that the underside of the module was sealed with a grey rubbery filler which I manage to pick away to reveal several square inches of simple SMD component and some active FET/transistors devices (actual pieces of silicon with bonding wires to adjacent PWB) bonded directly to the internal PWB and encapsulated inside transparent poly-resin. Closer examination showed that the two that were dead shorts looked visibly damaged under the clear coating where the bonding wires touched the semiconductor!
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