I need Dell GX60, GX260, and GX280 advise...

[jalari]

I work in the IT department at a call center and most of the operation computers are a GX series computer (Mainly GX280) and I have gotten quite proficient at replacing bad caps and restoring the PC to working condition. However there seem to be a select few I run into that still plague me.

The main problem I run into is after all caps that appeared to need replacing both on the mother board and the PS were replaced, I still get the orange blinking light of doom and cant figure out why. I am sure the problem is in the power supply because when I swap it out for a good one, it works fine.

I have done everything I could think of to find the problem but still nothing. My only thought is could there be caps that are bad but do not show the visual sign of it? Has anyone had experience with these systems and know of any other part that could go out but show no visual signs of it?

My experience with electronics is limited but I know the basics. I even have a tester to check the capacitance of caps but so far, nothing. Thanks!

[ipman]

Re: I need Dell GX60, GX260, and GX280 advise...

Is the ESR that matters. You can have caps which show normal capacity, but very high ESR.
Sometimes, higher ESR is associated with capacity loss, but not allways.
Maybe an ESR meter will pay off.

[PCBONEZ]

Re: I need Dell GX60, GX260, and GX280 advise...

Are you checking the power supply caps too?
.

[Toasty]

Re: I need Dell GX60, GX260, and GX280 advise...

>>after all caps that appeared to need replacing both on the mother board and the PS were replaced<<

and

>>My only thought is could there be caps that are bad but do not show the visual sign of it? <<

You've answered your own question.

Can't go by appearance. Must test each -or- replace all.

In the PSU, likely problem is the 5vsb circuit. I had 2 Dells this past month with that problem of the blinking orange light. Both were PSU related.

Toast

[jalari]

Re: I need Dell GX60, GX260, and GX280 advise...

Thanks for the replies. I have just been really stumped.

>>"Sometimes, higher ESR is associated with capacity loss."
Thanks, I'll look into that. I know the caps I purchased were supposed to be very low ESR but you never know plus other could be bad. I'll have to look up how to test ESR rating because I already had to convince mt boss to let me get a meter just to check the cap values. Maybe it will do ESR as well.

>>"likely problem is the 5vsb circuit"
I thought this too but I tested all the voltages and they were within tolerances so don't think that is it.

As for testing the caps, is there anyway to test the caps while they are still in the PS? I think I know the answer because when I try I get values that just make no sense and I assume its because of all the other connections it picks up in the layout. It will be a pain to unsolder every cap just to test them and it would be a waste of money to just replace them all. Thanks again!

[ipman]

Re: I need Dell GX60, GX260, and GX280 advise...

You cannot test the capacity in-circuit, just the ESR.
Remove the solder around one leg of the capacitor, make sure that it will not touch the PCB and then measure it. That's the best you can do.

[PCBONEZ]

Re: I need Dell GX60, GX260, and GX280 advise...

Contrary to what they say in ESR meter ads you often can't test for ESR in-circuit either.
Many mobo caps are in parallel with other caps.

That is almost guaranteed if one leg is on a PSU rail through the board.
Not many boards only have only one cap on a rail.
.

[ipman]

Re: I need Dell GX60, GX260, and GX280 advise...

Sure, PCBONEZ, you are right. But if it's only one, you can test the ESR on-circuit.
Altough, even there's only one cap, one cannot test capacity in-circuit anyway.

[PCBONEZ]

Re: I need Dell GX60, GX260, and GX280 advise...

Depends, might look like it's a single but not be.
Sometimes caps are in parallel and in completely different locations on the board.
Like - A cap near the RAM might be in parallel with one over by a PCI slot through the board.
You can make a good guess but you won't really know unless you've done continuity checks to all the other caps.
By the time you do all those continuity checks you might as well have saved the time and pulled the cap since you need it out to check the capacitance anyway.
.
In-circuit isn't a good way to say caps are -good-.
But if in-circuit shows -bad- you have at least one bad cap because to show as bad any caps in parallel with it are bad too.
.

[jalari]

Re: I need Dell GX60, GX260, and GX280 advise...

Thanks everyone for the replies. I ended up buying a Build You Own ESR tester on eBay. I assembled it and began testing caps that were inline on the power supply. After doing the tests, I found one cap who's ESR value was way off (around 26.0 and it should have been around 1.0). I pulled that cap off the board and tested it again. It came down to 15.0 so testing in line can affect the value it seems. I put a new cap in that had the right value and bingo, problem solved FINALLY!

THANK YOU ALL SO MUCH!!!! This has bugged me for a long time and the cap in question was a 35v 100uF cap that appeared perfectly normal visually and after testing it on a cap meter, also showed the correct value so clearly this ESR meter was worth every penny.

[PCBONEZ]

Re: I need Dell GX60, GX260, and GX280 advise...

Congrats!
.