Amiga 600 cap repair help

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coonsgm
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Amiga 600 cap repair help

Post by coonsgm »

Was fortunate to come across an A600 yesterday (bit of a rarity here in the US). Powered it up and all worked just great. Having just recapped my A1200, I figured I'd take a look at the caps on the new computer. My A1200 didn't look like it needed recapping with no signs of corrosion, so the whole process was pretty painless. Unfortunately, the A600 is in much much much worse condition (amazed it still worked). One cap even fell off after just touching gently.

Fast forward to the cap removal. One pad literally had disintegrated. I was able to salvage and clean up everything else (whew). I would appreciate any help here as I plan on my strategy to bodge to the new cap.

See image for what I think I should do (tried to do some homework myself first)

A600 cap wiring.png
A600 cap wiring.png (218.21 KiB) Viewed 1254 times
coonsgm
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Re: Amiga 600 cap repair help

Post by coonsgm »

I wrote Pin12, I meant Pin14
coonsgm
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Re: Amiga 600 cap repair help

Post by coonsgm »

Ignore my ignorance here :)

Looking like I'll recreate the pad....
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exxos
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Re: Amiga 600 cap repair help

Post by exxos »

If the pads gone just use the capacitor legs and bodge wires to the track.
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Badwolf
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Re: Amiga 600 cap repair help

Post by Badwolf »

coonsgm wrote: Sun Aug 07, 2022 7:32 pm Image
Why are you getting C409 involved? It shares no common positive side connection to C459.

Just run a line to VREF, either on U12 chip, to the trace, as exxos says or to C458.

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Maximilian
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Re: Amiga 600 cap repair help

Post by Maximilian »

You talked about the positive side of C409, but the only use would be the negative side of C409 as a GND connection.

If the GND of C459 is still there I would:
1. Solder a fine gauge wire to the positive side of the new C459 and preform it to pin 14 of U12.
2. Solder the negative side to the remaining negative pad of C459.
3. Hotsnot the cap.
4. Solder the wire to pin 14 of U12.
5. Measure and test.
6. Hotsnot the wire.

You can use http://amigapcb.org/ to visualize
coonsgm
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Re: Amiga 600 cap repair help

Post by coonsgm »

Thank you all for your help. It's alive and working. The pad recreation was the easy part. VCC was shorting to ground and after some hair pulling (I don't have enough to spare really) I found the source due to unseen damage under one of the other caps I had replaced.

The PCB explorer was a lifesaver (hair saver)
coonsgm
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Re: Amiga 600 cap repair help

Post by coonsgm »

Badwolf, I was getting C409 involved because I am a mechanical engineer and haven't read circuit diagrams since my undergrad just a few years ago.
Maximilian
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Re: Amiga 600 cap repair help

Post by Maximilian »

Nice to hear that you got it working :dualthumbup:
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