Indy Power Supply Replacement

When I first got the Indy, it seemed to work. When I pushed the power button,

A few weeks later, I got the right serial cable to attach a console, and…it no longer worked:

That’s pretty broken! I stoped trying to boot it (in case I was somehow damaging the electronics), and looked online for ideas. Apparently, a common problem with old Indys is the power supply failing. My Indy had the brand of power supply that was affected (Nidec) - it seemed like a plausible explanation. To dig a little further, I broke out the multimeter and checked the voltage on the Molex connector that normally goes to the hard disks - when I turned on the juice, the voltage was jumping all over the place.

I looked on eBay for replacement power supplies (a lot of old computers get parted out if something breaks), and found a Sony one - the brand that was supposed to be OK. Replacing the power supply once it arrived was super easy - there’s only one screw holding it in place:

the screw holding power supply in place

With that removed, you can slide the power supply apart from the rest of the chassis - it doesn’t sit inside the chassis, it sits next to it:

power supply next to chassis

In real life, I just popped the new power supply in and immediately tried it out, but in writing this post I checked out the voltages both power supplies put out. One thing that stood out to me was that the 12V rail (yellow wire) on the busted power supply…wasn’t reading 12V! On the broken one, it was at about 6V:

bad power supply only reads 6V

On the good one, it read a much healthier 12V:

good power supply reads 12V

The new power supply brought back the jingle and let me move on to the next thing: getting the OS booting! But what specifically was wrong with the power supply? I often see folks mention capacitors bursting as the cause of power supply failure. Though I’d love to crack open the bad power supply and see what I can see (and maybe re-cap it!), I’m not going to for now: