exxos's Atari, Amiga & retro forum

On my other post about the Atari 1050 I mentioned I was busy replacing the old sockets. Of course that meant removing the chips, so I decided I'd use my proper DIP chip extractor tool, rather than the cheapo U shaped but of metal, or my little chip pry bar tool.

As it turns out, I think the outcome would probably have been the same regardless of tool, which was the chip snapping in half, something I've not experienced before!!




This was rather annoying because I was actually getting somewhere with the repairs!!

So now I'm on the hunt for a new WD2793 formatter/controller chip, and I am wondering if the chip was already damaged hence why the drive wasn't recognised, but did allow the mechanism to initialise.

One odd thing is the fact it had covers on the top AND underneath (the silver and black covers) meaning the chip had a built in weakness in the middle.

I'll be watching out for that in the future!!

:o :o

I've just fried the SRAM on a 1541 I'm trying to diagnose, swapped all the main IC's out (which were socketed) and continue to get drive constant spinning and red LED, removed the SRAM (which wasn't socketed - hot air and desolder gun to protect the motherboard traces) tried it in my working drive and get a flash code. Swapping the good ram in and still get the same behaviour. So, I think it wasn't the RAM, but likely to be a 74 series logic chip at fault.

All fun and games aint it.

BennehBoy wrote: 31 Oct 2021 19:09 I've just fried the SRAM on a 1541 I'm trying to diagnose, swapped all the main IC's out (which were socketed) and continue to get drive constant spinning and red LED, removed the SRAM (which wasn't socketed - hot air and desolder gun to protect the motherboard traces) tried it in my working drive and get a flash code. Swapping the good ram in and still get the same behaviour. So, I think it wasn't the RAM, but likely to be a 74 series logic chip at fault.

All fun and games aint it.

Don't get me started, it's all been about the 5 1/4" drives lately, and I haven't yet checked if my own 1541 works after moving house! Thank god for SD2IEC in the meantime!

So I put my mechanical engineers brain to work and did a little post mortem.

Looking at the chip construction:


It's evident that this chip would have broken pretty much no matter what method you used to try and remove it.

Basically there is a huge hole in the middle where the die is, and the die sits on a metal plate over which is glued a plastic cover on the bottom. Above the die is yet another metal plate and plastic cover.

The plates and plastic covers offer no real physical strength, and the chip body, being 1mm thinner than other similar chips (3mm vs 4mm) is incredibly weak where the hole is at its widest, probably a 1mmx3mm cross section.

Add to that there are metal legs that pass through this section, further adding weakness to the structure as a whole. The chip failed at its weakest point.

All I can do now is find a replacement.

Looks like a Monday project to repair

Tom

Tomswork wrote: 01 Nov 2021 01:19 Looks like a Monday project to repair

Tom

:lolbig: