Well that was disappointing!!

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rubber_jonnie
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Well that was disappointing!!

Post by rubber_jonnie »

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!!


IMG_20211031_153252.jpg
IMG_20211031_153252.jpg (209.01 KiB) Viewed 2103 times


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!!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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exxos
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Re: Well that was disappointing!!

Post by exxos »

:o :o
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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BennehBoy
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Re: Well that was disappointing!!

Post by BennehBoy »

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.
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rubber_jonnie
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Re: Well that was disappointing!!

Post by rubber_jonnie »

BennehBoy wrote: Sun Oct 31, 2021 7:09 pm 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!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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rubber_jonnie
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Re: Well that was disappointing!!

Post by rubber_jonnie »

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

Looking at the chip construction:

IMG_20211031_231407__01.jpg
IMG_20211031_231407__01.jpg (182.38 KiB) Viewed 2029 times

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.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Tomswork
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Re: Well that was disappointing!!

Post by Tomswork »

Looks like a Monday project to repair

Tom
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Re: Well that was disappointing!!

Post by rubber_jonnie »

Tomswork wrote: Mon Nov 01, 2021 1:19 am Looks like a Monday project to repair

Tom
:lolbig:
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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