exxos's Atari, Amiga & retro forum

zChris wrote: 21 Sep 2021 10:57 I cant add a CPU and patch it with small cables?

(Sometimes this needs to be said)

I can, you can't.

I wouldn't, though, since the amount of work involved is higher than the cost of a new board.

But here's the positive: You _can_ get good at (de)soldering. It requires studying some theory (there are excellent solder technique videos on youtube) and a lot of practice. You need to understand how a PCB is put together (old and new .. ) to understand what happens when soldering and why a via suddenly "disappears".

You seem to have a lot of the right equipment, so while I agree with everyone else that this board isn't likely to boot again, you can definitely use it to train with.

/Troed

My little advice list for de-soldering:

• "If it does not easily come out, it isn't properly de-soldered yet"

• A properly de-soldered chip/socket should fall out with zero force, besides leg tension.

• If the solder is being troublesome, re-apply lead free solder before attempting again

• If you have a heat-gun, a short blast of hot air is an easy way to fully release a stubborn chip/socket

Great advices @Steve

@troed i take that as a challenge ;)

@zChris I hope you manage it but it will be a difficult repair for even an experienced electronics engineer.

Thanks @PhilC , it will mostly be a "winding down at the evening" project.

Regarding the capacitor, i should be able to replace it with this one https://www.electrokit.com/produkt/kera ... p0-2-54mm/ ?

/zChris

That quotes 1nf. Should be 100nf. But the capacitor is the least of your problems right now.

Most ST decoupling caps I've encountered are marked 104 where it's readable, so as exxos said, 100nF.

Whilst I understand your desire to fix it, as I've been in similar scenarios, if you're just going to use it for a donor board, then repairing it will not enhance your solder skills at all, and you may just end up with an unstable machine.

You're better using it as a training platform for de-soldering, and if you want to work on your general soldering skills, then buy some cheap electronic kits from eBay or Amazon to build.

ST mainboards are fragile these days, they are around 30 years old, so need to be handled with care to prevent unseen mechanical failures, such as cracked vias or tracks, plus they do not get on with overheating.