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Old 13 November 2018, 16:25   #1
trickywookie
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Amiga 2000 Rev 4.2 repair advice

I found an Amiga 2000 in my father's garage last Summer. I gave it a try and it booted up so I took it home. Two months later I found room for it and tried to turn it on again and it wouldn't show a workbench screen. The screen was alternating between different shades of gray, the power light was going between a brighter and darker red. Once it showed a guru meditation error but I didn't write the code down. There was no disk activity.



I removed all the (multiple) expansion cards but it didn't help. I did some reading about Amiga repair and learned that I'd better check out the battery. Unsurprisingly, the battery leaked and there was some corrosion on the motherboard around it, and on the closest 4 or 5 pins on the 68000. I tried to neutralize the corrosion with watered down vinegar and later isopropyl and put things back together. Now it doesn't even show the grey screen, it has a black screen and the power light is a solid red.



I'm linking some photos of the damage in hopes that someone may have some repair suggestions.


https://photos.app.goo.gl/A96JbLtWNcC1NJ1D9
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Old 13 November 2018, 16:30   #2
Jope
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That's not too bad, but you'll probably have to replace the 68000 socket.

Also you should use a multimeter to beep out all of the traces to the right of the 68000 socket to see whether they are still conducting.
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Old 13 November 2018, 16:42   #3
shaf
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That actually looks pretty clean, aside from ringing out the 68000 socket connections, and a few motherboard patches it should be good. Id offer to fix it for you but shipping would be very expensive, as i don't have and a2000 system, only A500 and A4000 in my work area.

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Old 13 November 2018, 17:11   #4
trickywookie
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Thank you for your comments Jope and Shaf. It has been a few years since I've done much soldering but this doesn't sound too scary.

Shaf: Moving to PEI from Waterloo definitely meant less qualified people in the area to do this kind of work Shipping this beast to Toronto would definitely be pricey. Excuse my lack of knowledge, but what did you mean by "ringing out the socket connections"? Is this the same as replacing the socket?

Is it likely I'll need a replacement 68000 as well?
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Old 13 November 2018, 18:01   #5
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Nah, just use the continuity mode on your multimeter to measure the traces. The 68000 is probably still fine, as long as the legs didn't fall off when you removed it, but I guess it isn't impossible for the corrosion to travel along the legs into the package.
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Old 14 November 2018, 04:38   #6
shaf
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By ringing out the connections is just using a multimeter to confirm the all CPU connections and traces around the socket are OK. To determine whether the socket requires replacement. There are a few fixes to rev 4.2 boards that would improve signal quality
such as - removing the trace from U801 Pin16 to Y800
- Lifting the U801 Pin 17
- add wire jumper from U801 Pin16 to Y800
- add wire jumper from U801 Pin 17 to C810
(This was the official Commodore Rev 4.4 fix to remove noise around the RTC Osc. )
From Service Bulletin C3-1.17

There was also a fix specific to the Phihong type A2000 Power Supply
From Service Bulletin C3-1.23
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Old 14 November 2018, 04:49   #7
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You could always just ship the PCB, not the whole computer. That's how MOST people do it. All Shaf needs is an atx to a2000 psu adapter to power it on his bench. It really doesn't look that bad at all. Check the socket connections Shaf and Jope suggest.
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Old 14 November 2018, 23:23   #8
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Thanks so much for the help folks! I'm going to do some continuity testing this weekend shaf, that service bulletin info is super helpful!
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