[vcf-midatlantic] Personal IRIS PSU repair

Jameel Akari jakari at bithose.com
Wed Feb 17 22:35:29 UTC 2021

Agreed, unless you’ve noticed something else failing, just assume bad caps and go from there. For the effort and marginal cost, I am just replacing all of them when I have a PSU apart.

One problem I’ve had on the IBM RS/6000s are case cooling fans that are stuck or slow - this causes the PSU to trip and it isn’t obvious this is happening. (Super fun when it’s VCF morning.) So if you have 3 or 4 lead fans, check those too.

The most tedious part so far has been just building the order - checking each old part, measuring dimensions, repeat. I have an Apple Xserve PSU apart on my bench still where I didn’t get perfect fits and now I have to figure out adjustments.

Also my new Hakko desoldering gun has been a revelation after 30 years of doing it the hard way. :)

Jameel Akari 

> On Feb 17, 2021, at 5:08 PM, Ethan O'Toole via vcf-midatlantic <vcf-midatlantic at lists.vcfed.org> wrote:
>> Yeah, probably something I should just do anyway.
>> There's a very fun spot where there are four caps soldered directly into two rails of sheet metal that I don't particularly look forward to dealing with...
>> Thanks for the info, on the Indigo 2!
> A friend gave me one of those 36" inkjet printers (DesignJet 1050C) a long time ago which had a similar PSU issue. Hair dryer to the PSU board brought it up. Then I just kept cutting the problem in half... which side of the board, which side of the half of the board, etc down to the one small cap that was at fault.
> Depending on the wiring/form factor if you can carefully bring it up easily you can replace some caps, test it, then go further. Usually the huge ones on the AC input side aren't replaced as part of a repair.
> My SGI Indigo had an issue that it was always reporting that the AC power was lost, which spams this message to console. In order to poke at the PSU I had to use one of those PC ATX power extension cables to get the power supply powered on outside of computer. Luckily even though it's not ATX pinout it's the same connector and I was able to use that to test. I figured out the fix, posted it to Nekochan and the site went down a few days later.
>            - Ethan

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