VP201b with bad inverter

[discsox]

First I want to thank you you guys for the great forum. It helped me wake up one VP201b from the dead. It had a blown inverter fuse...

Another VP201b does have a bad inverter board. I know this for a fact because I put the fixed inverter board into that monitor and it worked just fine.

The symptoms are as follows with the bad inverter. When I turn the monitor on the screen goes on for about a second then goes black; green light stays on for a while then goes to yellow.

So here are my questions:
- is there anything obvious besides the fuses and bad caps that could be wrong with the inverter board?
- Any place where I could find a replacement inverter board???

Here is what I checked:
- visually the board looks good including the caps... I was only able to measure the resistance of the caps and they were identical in the good and bad board.
- I do have 17.9V on the board at the fuses.

Any help is greatly appreciated.

Cheers, Marcello

[PlainBill]

Re: VP201b with bad inverter

First I want to thank you you guys for the great forum. It helped me wake up one VP201b from the dead. It had a blown inverter fuse...

Another VP201b does have a bad inverter board. I know this for a fact because I put the fixed inverter board into that monitor and it worked just fine.

The symptoms are as follows with the bad inverter. When I turn the monitor on the screen goes on for about a second then goes black; green light stays on for a while then goes to yellow.

So here are my questions:
- is there anything obvious besides the fuses and bad caps that could be wrong with the inverter board?
- Any place where I could find a replacement inverter board???

Here is what I checked:
- visually the board looks good including the caps... I was only able to measure the resistance of the caps and they were identical in the good and bad board.
- I do have 17.9V on the board at the fuses.

Any help is greatly appreciated.

Cheers, Marcello

eguevarae is the expert on the VP201b. Entering Lecture mode.

The backlight system has two parts, the inverter and the backlights (CCFLs and associated wiring). You have demonstrated that the backlights are fine. Well done! That leaves the inverter. The inverter generates the high voltage the CCFLs require AND monitors the voltage and current the CCFLs draw. The two possible failure areas are in the voltage generation circuitry and the monitoring circuitry. Exiting lecture mode.

Common failure items: Drivers (usually results in a blown fuse), transformers, solder joints on transformers, diodes in current sensing circuit.

The first suggestion is to solder every pin on every transformer on the inverter; don't rely on a visual examination, resolder. If that fails to fix it, examine the wires going from the inverter to the CCFLs. Notice that one of the wires is of a smaller diameter - that is the return line. Examine the connectors - can you touch the contact for the return line with a probe? Check the specs on your DMM - will it measure 100 khz AC signals? If so, you are ready to do a test.

WARNING!!! A mistake here will very likely destroy your DMM and give you a shock. Be very careful; your self esteem is at risk.

Set the DMM to measure AC volts. Measure the AC voltage between the metal LCD frame and the CCFL return lines where the exit the connector. Do NOT allow the proble to come in contact with the drive line. If any of the return lines is at a different voltage, you have identified which section has the problem.

Post pictures of both the front and back of the inverter.

PlainBill

[discsox]

Re: VP201b with bad inverter

Thank you very much for taking the time to write a detailed response.
I re-soldered all the transformer pins and sure enough the monitor is working again!!!

With you guy's help I was able to fix 2 dead monitors that have been sitting in my office for a LONG time. Just could not get myself to recycle them and now they are perfectly good again
You guys are awesome.

I replaced the fuse on one a 3rd VP201b and it worked for about a day then the fuse blew again and the display went black.
Not quite sure what to do about this one...
I will replace the fuse as soon as I get some Pico fuses (they are on order) and give it another try.

Cheers Marcello

[EGuevarae]

Re: VP201b with bad inverter

Thank you very much for taking the time to write a detailed response.
I re-soldered all the transformer pins and sure enough the monitor is working again!!!

I was reading the new threads and was about to suggest the resoldering and the post of inverter input (voltages) but I was too slow for Bill....

For the other unit, resolder and post a pic of the inverter board so I/we can see what model it is (I've seen three different ones for sure on the VP201/211 series).Even better, if I have one exactly like yours I can even send it to you if possible

Also, I would recommend that you check the caps on the power supply, as they are likely to fail (if not already recapped).

[discsox]

Re: VP201b with bad inverter

Thanks for replying.
Attached are the pictures of the board where the fuse failed after a day.
I will re-solder and replace the fuse.
If it's a bad driver it might be difficult to pin-point. If you have a replacement board that might be very helpful.

I will post back as soon as I have some more news.

Thanks again!!!

Marcello

[EGuevarae]

Re: VP201b with bad inverter

Thanks for replying.
Attached are the pictures of the board where the fuse failed after a day.
I will re-solder and replace the fuse.
If it's a bad driver it might be difficult to pin-point. If you have a replacement board that might be very helpful.

I will post back as soon as I have some more news.

Thanks again!!!

Marcello

Will look the parts box. I'll let you know if I have a working one that you can use.

[discsox]

Re: VP201b with bad inverter

Thanks a lot for checking - you

Happy Thanksgiving!!!

[discsox]

Re: VP201b with bad inverter

Just wanted to give an update.
Replacing the original SMD fuses with "resistor type fuses" from digikey.com (FUSE PICO FAST 2A 125V AXIAL ) fixed the monitor for now.

So I have 3 working monitors again which is great!!!

Thanks again for all the help.

Cheers, Marcello

[EGuevarae]

Re: VP201b with bad inverter

Just wanted to give an update.
Replacing the original SMD fuses with "resistor type fuses" from digikey.com (FUSE PICO FAST 2A 125V AXIAL ) fixed the monitor for now.

So I have 3 working monitors again which is great!!!

Thanks again for all the help.

Cheers, Marcello

Which fuse did you use the first time?
What about the caps on the power supplies?

[discsox]

Re: VP201b with bad inverter

Which fuse did you use the first time?

I un-soldered an original SMD fuse from the inverter of the second monitor. It may have been damaged slightly in that process. But this is just a guess.
Before I got the Pico Fuses I used regular fast acting fuses in a standard fuse holder for testing. Which works fine for just that purpose because it takes some time to order the Pico Fuses. I was not able to find them locally in any store.

What about the caps on the power supplies?

I did a visual inspection of the caps and there was no bulging or leaking. Also the output voltage was stable at 17.9V.

The monitor is currently not in use but it will be shortly (I had it running for about 24h initially without issues). I'll post back in case I have some issues.

Cheers, Marcello