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[retiredcaps]

Re: No image

So would both VRs be bad on the bad board? Or is something else causing the voltages to be off?

I have a logic board in front of me and both VRs are bad. So yes, it can happen.

If you have a schematic, please post a link to it.

[bsweasel]

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What is the actual input voltage on all pins? You measured 5V DC on the connector and I just want to see what is going into the regulator.

Input voltage on good board is U102 5.05v and U101 4.77v
Input voltage on bad board is U102 5.06v and U101 4.80v
Using the same PSU board.

[retiredcaps]

Re: No image

Input voltage on good board is U102 5.05v and U101 4.77v
Input voltage on bad board is U102 5.06v and U101 4.80v
Using the same PSU board.

You might have 2 problems here given your measurements.

1) The output readings suggests you have 2 bad voltage regulators.

It is my understanding that regulators are pretty much "jellybean" parts. That is, you can find them everywhere. So if you have scrap boards, take a look for handy replacements.

2) The capacitors on the logic board could be bad and causing the "sub 5V" readings.

[EGuevarae]

Re: No image

...

2) The capacitors on the logic board could be bad and causing the "sub 5V" readings.

This has happened to me more than once in the past

[bsweasel]

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schematic is in this pdf link from acer.com near the bottom of the document.

With the input voltages being nearly the same between the two boards, wouldn't that suggest that the caps are ok, and the VR's are the problem?

[retiredcaps]

Re: No image

Input voltage on good board is U102 5.05v and U101 4.77v
Input voltage on bad board is U102 5.06v and U101 4.80v

With the input voltages being nearly the same between the two boards, wouldn't that suggest that the caps are ok, and the VR's are the problem?

"Nearly the same" is really not.

It is likely the 5V is regulated which means the voltage should be really close to 5.00V DC.

5.05 is within 1%. 5.06 is within 1.2%.

4.77 is within4.6%. 4.80 is within 4.0%

I would suggest replacing the regulators first. If that doesn't solve the problem, then replace the caps. If shipping costs are high, then order both.

[bsweasel]

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I found a donor board to get me the 1117-3.3v regulator, swapping that into the circuit gives me a solid 3.3 volts on the output of U101.

I had to order a new 1.8v regulator from digikey today since I couldn't find one to scalp, so we will have to wait for the verdict. I'm learning....very slowly.....but learning non-the-less! Thanks to everyone so far for all the guidance, and to the owners of badcaps....this is a great place.

[bsweasel]

Re: No image

U101 is dishing out 3.26v on the good board and 3.75v on the bad board.
U102 is dishing out 1.79v on the good board and 1.20v on the bad board.

Input voltage is the same on both boards.
Schematic says U101 is 3.3v output and U102 is 1.8v output. So would both VRs be bad on the bad board? Or is something else causing the voltages to be off?

Results: Both Voltage Regulators on logic board bad!

Donor Regulator now in U101 is putting out consistent 3.3v. And new LM117MP-1.8CT-ND from Digikey in position U102 is outputing 1.78v.
Monitor now powers on and displays an image. Fixed!

Thanks everyone!

[retiredcaps]

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And new LM117MP-1.8CT-ND from Digikey in position U102 is outputing 1.78v.

I'm envious of the cheap and fast shipping service you guys in the USA get from digikey for $2.75 ish.

With gas over $1/L here, it doesn't make much to waste $2.75 driving around looking for voltage regulators.

[bsweasel]

Re: No image

I'm envious of the cheap and fast shipping service you guys in the USA get from digikey for $2.75 ish.

With gas over $1/L here, it doesn't make much to waste $2.75 driving around looking for voltage regulators.

We envy your low crime rate and government health care!! But lets not open that off topic can of worms!!