Optiquest 20qw power supply problems..

[ampapa]

Hello, my first post to the forum!

I was hoping I might find some expert advice in diagnosing the problem with my Optiquest 20QW monitor with the dreaded or should I say common bad capacitor issue.

A little background on the monitor first. Everything was fine, had been using it occasionally on and off for the past year so its not a dedicated work station. I powered it off last week after normal usage and went to turn it back on and it wouldn't power on, simple as that.

So, after a little poking around on the internet I found that this is a pretty common problem and I should just recap the power supply, I did that however I still have no signs of life. I used VHT Series High Temperature cap, I think those are OK to use.. I also used 1000uf 25v for (C241, C244) as that was all I could find for those I also think the higher voltage shouldn't matter, but I'm a novice to say the least.

I found a schematic for the "power" section of what I believe is the correct board in the thread on the forum (https://www.badcaps.net/forum/showthread.php?t=21557) and I was able to test for power at the 5+ and 12+ with 11.78 and 5.2 respectfully.. after that I'm not sure where to go.. hopefully someone can give a nudge.

Thanks.

ampapa,

[budm]

Re: Optiquest 20qw power supply problems..

https://www.badcaps.net/forum/attach...2&d=1493993151
So that black rectangular shape fuse by the connector that goes to the main board is good? How about pictures of the whole unit showing how all the boards are connected together? BTW, no indicator lights at all either?

[ampapa]

Re: Optiquest 20qw power supply problems..

https://www.badcaps.net/forum/attach...2&d=1493993151
So that black rectangular shape fuse by the connector that goes to the main board is good? How about pictures of the whole unit showing how all the boards are connected together? BTW, no indicator lights at all either?

I'm guessing yes the fuse is good as I was able to pull my voltages from the connector that goes to the panel. No, there is no indication that the unit has power when plugged in, the power button has no effect.

Here are some additional pics... some are pre cap replacement. I also think I have the schematic, but I must admit its a bit greek to me.

ampapa,

[budm]

Re: Optiquest 20qw power supply problems..

OK, you need to look for SMD fuses if it has some on that main-T-CON combo board.

[ampapa]

Re: Optiquest 20qw power supply problems..

OK, you need to look for SMD fuses if it has some on that main-T-CON combo board.

I see 2 fuses on the board and both check for continuity. The Buss ss-5 is on the 5v leg of the connector which test for 5.2v and the other (round/brown) also tests OK, I believe it fuses the mains.

Any other ideas?

[budm]

Re: Optiquest 20qw power supply problems..

I am talking about the fuses on the Green board.
https://www.badcaps.net/forum/attach...5&d=1494004778

[ampapa]

Re: Optiquest 20qw power supply problems..

I am talking about the fuses on the Green board.
https://www.badcaps.net/forum/attach...5&d=1494004778

Ah, I have not.

Just a quick glance at the schematic and I see the Scaler and VGA sections contain what appear to be 5 fuses?

Is there a quick way to identify the SMD fuse locations and or parts and is there a quick way to test them?

With the Power Supply supplying 5+ and 12+ on the connector does this somewhat isolate the problem to the "main-T-CON" board?

Thanks,

[ampapa]

Re: Optiquest 20qw power supply problems..

I only found 1 fuse on the board, F1, tested it in place and it has continuity.

[ampapa]

Re: Optiquest 20qw power supply problems..

A quick question....

When testing this monitor, will it power up, light the power LED, without it being connected to a PC?

I think I've read that I won't get an image unless its hooked up but I'm under the impression it will at least power up without it being connected.

ampapa,

[budm]

Re: Optiquest 20qw power supply problems..

The power supply is always running, the monitor will go into standby in a few minutes or seconds (depend on the design) if it does not detect video signal from the PC. Most monitors the power LED may be green when monitor is first turned on and yellow when it is in standby mode

[ampapa]

Re: Optiquest 20qw power supply problems..

Thanks for the confirmation.

So, I can better try to decipher what the problem is can you answer a few nagging questions I have?

1) I replaced the old CAPs with high temp VHT series CAPs (available) are they compliant with the ESD ratings that are needed, maybe this is my problem?

2) Since I have 12v and 5v at the connector for the "green" board does this mean the PS is doing its job? If so, then I could eliminate question 1 as a problem.

3) Do you see a problem with replacing the 1000uf 10v with a 1000uf 25v? I was under the impression this was an acceptable practice assuming space allows for the difference.

4) I've seen mention of a "Starter" cap on the PS board which I believe is a 22uf 50v, I did not change this one, could this be my problem?

5) Since its obvious the caps were bulging, leaking and were a necessary repair as well as the fuses are good on both the PS board and the "green" board. Do you have any other suggestions that I might look for?

Thanks for your insight.

ampapa,

[budm]

Re: Optiquest 20qw power supply problems..

Thanks for the confirmation.

So, I can better try to decipher what the problem is can you answer a few nagging questions I have?

1) I replaced the old CAPs with high temp VHT series CAPs (available) are they compliant with the ESD ratings that are needed, maybe this is my problem?

2) Since I have 12v and 5v at the connector for the "green" board does this mean the PS is doing its job? If so, then I could eliminate question 1 as a problem.

3) Do you see a problem with replacing the 1000uf 10v with a 1000uf 25v? I was under the impression this was an acceptable practice assuming space allows for the difference.

4) I've seen mention of a "Starter" cap on the PS board which I believe is a 22uf 50v, I did not change this one, could this be my problem?

5) Since its obvious the caps were bulging, leaking and were a necessary repair as well as the fuses are good on both the PS board and the "green" board. Do you have any other suggestions that I might look for?

Thanks for your insight.

ampapa,

1) May be you are talking about ESR? Where are the spec sheet of the caps you are using?
2) The power supply section si working otherwise you will not have the 5V/12V.
3) You are really not gaining any thing by increasing the Voltage to 25V for the 5V power supply section.
4) Startup running cap must be OK otherwise you will not have the 5V/12V but you should change it anyway since it is one of the commonly fail cap.
5) Not much suggestion for testing the main green board. May be looking for burnt part, blown fuse (which you already tested), Voltage regulator ICs, etc.
Right now the indicator lights should at least be on if the main board is alive at all since it has 5V to run it the logic section.
BTW, did you ever see the backlights even flash on for seconds?