Care and feeding of your power supply

[Matt_H]

I'd been having trouble with they keyboard on my 4000T - dropping dead randomly, sending garbage input, and other symptoms that make it unusable. I replaced 2 of the capacitors within the keyboard, and that seemed to help, but it had no actual effect. My tests post-replacement were both false positives for success.

Today I started stripping down the machine, desperately trying to figure out what other component might be broken and interfering. I was getting nowhere, until I pulled the motherboard power leads on a whim. Yikes! The 5V rails are all fried. I'll bet money that this is the problem.

I installed this PSU in 2006. I thought that I would have gotten a little more life out of it (the original one lasted from manufacture in 1996 until my replacement). Is this damage to the leads indicative of something to do with my machine, or was this just a crappy PSU? It's 300W, driving a CSPPC, 2 hard drives, 2 CD drives, and 5 Zorro cards.

[Matt_H]

I don't trust myself to be able to replace the connectors correctly, either on the motherboard or the PSU itself. I've got a replacement PSU coming in the mail - any suggestions on what I can use to polish up the motherboard connectors? Good ol' isopropyl alcohol, maybe?

EDIT: Just to clarify, the keyboard is actually fine (I think) - it's working on another machine.

[Matt_H]

Thanks, all. There's no obvious damage to the motherboard connectors, but I will take a closer look tonight and report back.

[Matt_H]

Well, there was some discoloration of the 5V pins on the motherboard. I rubbed them down with a cloth and an eraser as best I could (I know I didn't get everything) and then replaced the PSU. Everything seems to be stable now, but I'll be keeping a close eye on these things in the future.

Lesson learned: if your keyboard is doing insane things and your Caps Lock light is going crazy, check your power supply!

[Matt_H]

Stable now, fireworks tomorrow.. :p

Let's hope not!

Great to hear that it seems to be sorted! From using various "exotic" power supply setups on my Amigas, I can attest to that. I often got crazy keyboard behaviour (caps lock light flashing, stuck keys, random gibberish) on an A1200 until I checked the PSU with a scope and found it had some high frequency noise on the +5V line. Didn't affect anything else so far as I could tell, but eliminated the noise and the keyboard started working again. That one took a while to sort out!

Yup, those were the exact symptoms I had. And now that I think about, I believe the same thing happened on my old 1200T system many years ago. I ended up not fixing it, though, since that machine was replaced with this 4000T around the same time.

So now we've got the solution. Hopefully people with similar problems in the future will be able to find this thread!