Yesterday I picked up a Dell 30" monitor, model 3007WFP. It looks in good shape except the upper half of the screen has no backlighting. I googled around and found what little I could (no schematics to be had) and then took the covers off to have a look. The inverter board has 8 high voltage transformers on it and only the lower 4 are working. I'm from the mechanical world, not the electronic, but I have some experience. The board seems to be basically two pretty identical halves and I feel very fortunate that I can compare the working half to the non-working half or I would be in over my head immediately.
Logically, of course, I am looking for a pair of something since half the board works and half doesn't. It looked to me like the highest things in the chain are the two BD9886FV DC-AV inverter control ICs so I started comparing things there. I found a number of voltages that did not match from one to the other. All the readings are DC volts using my Fluke meter to chassis ground except the FET drivers where I used my scope. The working chip had square waveforms that looked pretty square to me aside from the fuzzy high-frequency noise I see all over. The non-working upper chip has no waveforms at all on those pins. The inverter board has no caps other than SMD, the power supply to the board is about 24 VDC and appears pretty clean on the scope. No visible clues on the board. I will appreciate greatly any informed opinions as to whether the problem might be internal or external to the chip, thanks in advance. Here is what the readings were with the significant differences highlighted:
Here is a scan of one of the chips and surrounding area (1280x1280 is very limiting!):
Thanks very much for looking.
Rob
Logically, of course, I am looking for a pair of something since half the board works and half doesn't. It looked to me like the highest things in the chain are the two BD9886FV DC-AV inverter control ICs so I started comparing things there. I found a number of voltages that did not match from one to the other. All the readings are DC volts using my Fluke meter to chassis ground except the FET drivers where I used my scope. The working chip had square waveforms that looked pretty square to me aside from the fuzzy high-frequency noise I see all over. The non-working upper chip has no waveforms at all on those pins. The inverter board has no caps other than SMD, the power supply to the board is about 24 VDC and appears pretty clean on the scope. No visible clues on the board. I will appreciate greatly any informed opinions as to whether the problem might be internal or external to the chip, thanks in advance. Here is what the readings were with the significant differences highlighted:
Here is a scan of one of the chips and surrounding area (1280x1280 is very limiting!):
Thanks very much for looking.
Rob