[roach-commuter]

Just found this gem on Ian's website. Perhaps it may be of some help

Reconditioning a failed Indigo2 power supply

[synthetix]

I haven’t gotten to these PSU models yet. However, most of the time, the twitching or attempt to start indicates a problem on the secondary (low voltage) side of the PSU and/or somewhere along the feedback circuit.  So likely the high voltage side isn’t the main issue (doesn’t mean it’s without any problem, just ones that prevent initial startup).

While I know this PSU is a pain due to its design. If it were on my bench I’d do two things immediately to check. 

Thanks! I'll definitely try out your suggestions. I don't think the high voltage side is the problem, either--but only because I didn't notice any damage or leaky caps on the HV side. All the obvious issues I found (leaky caps, corrosion) were with the low voltage side. So I'll concentrate my search there.

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Just found this gem on Ian's website. Perhaps it may be of some help

Reconditioning a failed Indigo2 power supply

Yep, I tried this initially, but it didn't make a difference. I actually contacted him about this, and he confirmed he had similar problems with some of his PSUs where replacing caps didn't help. So there are some other troublemaker components in there that may not be so obvious.

[weblacky]

Also, something else I don't have too much current experience with is the PSU start circuit. Normally this is done with a HIGH value LARGE resistor, a Cap, and a diode. That large cap takes quite a beating and can drift or go open. If that cap isn't correct the management IC won't start the PWM process currently. Normally for startup issues, this is where you also want to focus.

Easiest way to FIND the management IC (datasheet will say something like a power supply management IC or power supply PWM chip), from it's legs, you'll find the startup resistor (large) and can check that out of circuit. If you can also leave the PCBs connected outside the metal frame, you could also find a way to solder on and clip on a probe lead to the management chip's voltage input pin (there may be two of them, one for a bootstrapping/kickstarting, one for main Chopper run). You want to measure the voltage of the pin that's used to use standby (primitive) AC/DC conversion to kickstart the PSU. It won't kickstart if that simple passive system that powers that pin is off. Measuring that pin while plugged in will tell you what it's being feed (right or wrong).

[synthetix]

Another update. I managed to find a working power supply to use as a control. Installed it in the Indigo2, and sure enough the machine booted right up. So, that eliminates any possibility that the symptoms I seeing with the twitchy fans was related to anything else but the power supply. So that's a good thing!
Once I can get some outside help with repairing the original power supply I'll of course report back what the problem was.

[marmotta]

Another update. I managed to find a working power supply to use as a control. Installed it in the Indigo2, and sure enough the machine booted right up. So, that eliminates any possibility that the symptoms I seeing with the twitchy fans was related to anything else but the power supply. So that's a good thing!
Once I can get some outside help with repairing the original power supply I'll of course report back what the problem was.

I have some working Indigo2 8001 psu and one 8002 died... initially it shutdown with load, then it never powered up... I replaced the HV caps and it resurrected! But the voltages are quite low (11v instead 12v). Today I have replaced all caps of LV board and now is still dead 

This psu is the devil! Any information you can find is precious ;-)

[synthetix]

I'm starting to think it's not the caps that are the main problem. It may be a faulty thermistor or some component(s) involved in power regulation. Since I have a working replacement now, I can afford to tear down the broken one and experiment. Once I get some time...

[marmotta]

But... the three red caps marked 330uf 6.3v are “special” caps? The caps are sealed and my measure tools give me a random values.

[synthetix]

But... the three red caps marked 330uf 6.3v are “special” caps? The caps are sealed and my measure tools give me a random values.

I noticed those too. I'm not sure what the deal is with those red caps or why they're obviously different from the rest. Did you try measuring them out of the circuit?

[marmotta]

But... the three red caps marked 330uf 6.3v are “special” caps? The caps are sealed and my measure tools give me a random values.

I noticed those too. I'm not sure what the deal is with those red caps or why they're obviously different from the rest. Did you try measuring them out of the circuit?

Yes, I have done that, give me a random capacitance. I have substituted all thee caps but with no luck, now I have resoldered the red caps... still no luck :-(

[marmotta]

In my case I found the issue, is the motherboard... I need to investigate to found where is the problem.

Edit: is not the motherboard, simply don’t start without graphic board... is strange, but it is.