Hello all - I was given an HP PL4260N plasma that had the common sound issue, but no pic. I found the 4a fuse at FS2 open. Replacing the fuse caused the power supply to go in to protect mode. Unplugging the connector from the PS to the YSUS gave me back ~190v at the VS pin of the loose connector.
At the YSUS board, I measured a dead short between VS and ground pins. I pulled the YSUS board and found one of the FET's was shorted. I pulled both of the W9NK70Z FET's and sure enough, one was shorted. The other I tested as follows using a DMM on auto/ohms:
- Connect the 'Source' of the MosFet to the meter's negative (-) lead.
- First, touch the meter positive lead to the MosFet's 'Gate'.
- Now move the positive probe to the 'Drain'. You should get a 'low' reading. The MosFet's internal capacitance on the gate has now been charged up by the meter and the device is 'turned-on'.
- With the meter positive still connected to the drain, touch a finger between source and gate (and drain if you like, it does not matter at this stage). The gate will be discharged through your finger and the meter reading should go high, indicating a non-conductive device.
The other FET tested ok.
After some reading, I took a leap and assumed the IPM was bad. I pulled the old one (could write an article on doing that carefully and without damage) successfully, and sure enough - it was physically 'blown". See left had side of the bottom where two of the components are lifted right off the board - and included black marks on the YSUS board.
I also checked the board for bad caps via an ESR tester - and also a meter for shorts.
So I ordered a new IPM module, ceramic fuses and a pair of the W9NK70Z FET's. The parts arrived and I installed the new IPM (could write an article on doing that carefully and without damage), and replaced both FET's. I checked all my work and connections, no short to VS, and fired it up.
The PS went in to protect. I checked everything again, applied power and this time the fuse popped. After a 2 hour break, I came back and one of the new FET's was shorted. I pulled the YSUS board again - checked again for any issues - including the buffer board. The buffer board shows no sign of physical damage - and doing a simple ohms test between connector fingers does not show or different reading between the two side of the buffer board.
I replaced the second bad FET with the one good one I pulled earlier and same issue - PS goes in to protect. I now read 365k between VS and ground - seems low...
So - all I can think of is that I either have a bad IPM, or something else is wrong on the board. The IPM was purchased from a trusted vendor and sold as new.
Any advice? Words of encouragement?
At the YSUS board, I measured a dead short between VS and ground pins. I pulled the YSUS board and found one of the FET's was shorted. I pulled both of the W9NK70Z FET's and sure enough, one was shorted. The other I tested as follows using a DMM on auto/ohms:
- Connect the 'Source' of the MosFet to the meter's negative (-) lead.
- First, touch the meter positive lead to the MosFet's 'Gate'.
- Now move the positive probe to the 'Drain'. You should get a 'low' reading. The MosFet's internal capacitance on the gate has now been charged up by the meter and the device is 'turned-on'.
- With the meter positive still connected to the drain, touch a finger between source and gate (and drain if you like, it does not matter at this stage). The gate will be discharged through your finger and the meter reading should go high, indicating a non-conductive device.
The other FET tested ok.
After some reading, I took a leap and assumed the IPM was bad. I pulled the old one (could write an article on doing that carefully and without damage) successfully, and sure enough - it was physically 'blown". See left had side of the bottom where two of the components are lifted right off the board - and included black marks on the YSUS board.
I also checked the board for bad caps via an ESR tester - and also a meter for shorts.
So I ordered a new IPM module, ceramic fuses and a pair of the W9NK70Z FET's. The parts arrived and I installed the new IPM (could write an article on doing that carefully and without damage), and replaced both FET's. I checked all my work and connections, no short to VS, and fired it up.
The PS went in to protect. I checked everything again, applied power and this time the fuse popped. After a 2 hour break, I came back and one of the new FET's was shorted. I pulled the YSUS board again - checked again for any issues - including the buffer board. The buffer board shows no sign of physical damage - and doing a simple ohms test between connector fingers does not show or different reading between the two side of the buffer board.
I replaced the second bad FET with the one good one I pulled earlier and same issue - PS goes in to protect. I now read 365k between VS and ground - seems low...
So - all I can think of is that I either have a bad IPM, or something else is wrong on the board. The IPM was purchased from a trusted vendor and sold as new.
Any advice? Words of encouragement?
Comment