I have this rather smart 32" Plasma set. It was dead, cycling from standby/on then standby every second or so.
Checks revealed short IGBT's on the Combined X/Y SUS board. (That tiny 'X-SUS' isnt really anything more than two diodes and a couple of caps)
Its the X-SUS part of the circuit thats failing. Q603 and Q604 'Sus-Up' and Q18, Z-Ramp that go short-circuit. These are GT30F122, a 30A 300V IGBT by Toshiba.
I replaced these with the GT45F122, a 45A 300V IGBT by Toshiba. Both these parts are designed for PDP service, and not had issues subbing these in the past for the 30A version....
First time round, after replacement, the set ran for 15 minutes, then all three short again.
After that, I de-cased the panel and checked very closely for any abnormalities of the display surface, Spots or burns, and the Mylar connections/tabs to the panel. All appears fine.
After much testing and a few caps replaced/dry-joints resoldered etc and the three replaced again, along with a 2.2 ohm resistor this time that had also failed, (R22, supply from Vs to the 'VSC' inverter amongst other things) the set ran fine for firstly 1 hour, then next day for three hours, then turned off off for 10 minutes and then on again for another 3 or 4 hours.
This morning, set ran for an hour or so, then again a small 'Tick' and no picture followed by the PSU relay and back to standby.
Checks again show the same three IGBT's short-circuit. When working, the set gave a good picture although the black-level was a little high for a plasma, but not really objectionable.
The three IGBT's are connected, first two in parallel fed from Vs, the sources of these to the drain of the Z-Ramp one, and the joint between 'em to the ERC coil, and by the multi-way thick leads over to the Z-SUS diode-board attached to the Z-tabs.....
I'm thinking somehow the timing/drive to these is failing/corrupted for an instant leading to shoot-through and shorting....
Any ideas what would be causing this...?
Checks revealed short IGBT's on the Combined X/Y SUS board. (That tiny 'X-SUS' isnt really anything more than two diodes and a couple of caps)
Its the X-SUS part of the circuit thats failing. Q603 and Q604 'Sus-Up' and Q18, Z-Ramp that go short-circuit. These are GT30F122, a 30A 300V IGBT by Toshiba.
I replaced these with the GT45F122, a 45A 300V IGBT by Toshiba. Both these parts are designed for PDP service, and not had issues subbing these in the past for the 30A version....
First time round, after replacement, the set ran for 15 minutes, then all three short again.
After that, I de-cased the panel and checked very closely for any abnormalities of the display surface, Spots or burns, and the Mylar connections/tabs to the panel. All appears fine.
After much testing and a few caps replaced/dry-joints resoldered etc and the three replaced again, along with a 2.2 ohm resistor this time that had also failed, (R22, supply from Vs to the 'VSC' inverter amongst other things) the set ran fine for firstly 1 hour, then next day for three hours, then turned off off for 10 minutes and then on again for another 3 or 4 hours.
This morning, set ran for an hour or so, then again a small 'Tick' and no picture followed by the PSU relay and back to standby.
Checks again show the same three IGBT's short-circuit. When working, the set gave a good picture although the black-level was a little high for a plasma, but not really objectionable.
The three IGBT's are connected, first two in parallel fed from Vs, the sources of these to the drain of the Z-Ramp one, and the joint between 'em to the ERC coil, and by the multi-way thick leads over to the Z-SUS diode-board attached to the Z-tabs.....
I'm thinking somehow the timing/drive to these is failing/corrupted for an instant leading to shoot-through and shorting....
Any ideas what would be causing this...?
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