32-bit acorn hardware • Re: Magic Smoke from my 'new' A3000 :-(

Small update here, I've got the board out of the cupboard and have been assessing the damage a bit. I definitely need a new donor machine, but:

• I've desoldered the socket that I soldered in backwards. May as well fix it along with everything else.
• I might be wrong, but I figure the oscillator crystals are the most fragile non-IC components so I've removed those to be replaced.
• I've snipped off the massive fuel tank RAM capacitors (rated for 25V) - I'll take the opportunity to replace them with smaller ones.

The snipped off capacitors seem like they actually survived, after some probing with a multimeter. Which gives me hope that none of the other capacitors have blown; the radial electrolytics were also rated for 25V and none of them look damaged or leaky, and there's no short between +5V and 0V. The other through hole capacitors had higher voltage ratings.

I'm not sure about the transistors for the video/sound output, I think those can be sensitive to voltage but only between certain legs? I will have to do some probing as I rebuild.

I've also been doing continuity tests between various pins of various sockets. Something that really confused me is that the leftmost RAM chip IC20 is actually data bits 4 to 7, not bits 0 to 3. IC21 and IC20 are effectively swapped in order. Something to keep in mind - I thought I was going mad!

Thanks again everyone for the encouragement and advice. Here's hoping I can update with success one day!

Statistics: Posted by edmundmk — Sat Jan 24, 2026 11:05 pm

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