Amiga 2000 doer-uppers

robin-elvin

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I bagged a couple of A2000s in non-working condition last week. I've always wanted one so after buying one of the seller I decided to take the other one he had in order to make at least one working one.

Anyway onto the pr0n....

e9a3a3a4.jpg

yqy3edyv.jpg


Both machines only show a black screen when switching on.

First one is a rev 4.4 board. Second is a rev 6. Both have Kickstart 2.04 roms.

Dunno what the odd lead is on one of them. Perhaps someone can tell me or if either have other mods.

I moved the cpu from one to test which is why it's missing in the photo.
 
If you can, try and get the Rev.6 board running as it's more useable and less limited than the 4.4. I can;t really suggest much as I don't have a 2000 (but the recent swap should change that very soon!).

Best of luck.
 
Either dead cpu, crystal or Agnus if it's a total black screen.

They may have battery acid damage under the 68000 socket.

I can't tell from the photo's, I need hi res photos for that to see what the mods are.
 
Starting with the rev 6 board there was a lot of corrosion in the cpu socket. Cleaned it up a bit. I don't know whether it was instinct but I swapped the cpu from the other board and pressed down very hard in it while booting and it works. If I let up the pressure it immediately crashes. Tried the original cpu but that doesn't want to work.

So looks like a new cpu socket.

Sent from my GT-I9300 using Tapatalk
 
I'm interested to follow your project...I'm still playing with the 1200s and 4000s I have but after that I've got a lonely looking 2000 to tackle :)
 
If you don't fancy doing it yourself I can highly recommend bebek's motherboard refurbishments, he recently fixed my dead A4000 board.
 
I'm interested to follow your project...I'm still playing with the 1200s and 4000s I have but after that I've got a lonely looking 2000 to tackle :)

I'll make sure I post progress along with pictures. Currently it looks like the rev 6 board has a corroded CPU socket which needs replacing and it had a dead CPU. Hopefully that's all that's wrong.

I think the rev 4.4 board is going to need a lot more work. It's got more corrosion damage (although the CPU socket looks better which is probably why the CPU survived) It also appears to have had a new Denise - 8362R8 4589 - obviously not contemporary with the board. Also looks like a new CIA from '89 along with one from '87 which is probably original.
 
socket is on its way...

if i had known you needed a cpu i would of popped one in there with the socket:LOL::picard

oh well.
 
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socket is on its way...

if i had known you needed a cpu i would of popped one in there with the socket:LOL::picard

oh well.

Damn! I nearly mentioned it but I thought I may have to source more than just a CPU for the other board so no worries :)
 
Well the other cpu actually works and I don't have to lean on it to make the machine work now :)
I expect all the cpu swapping has rubbed some of the crud from the contacts. Once the socket is replaced with a shiny new one courtesy of roy_bates it'll be working fine.

The other board is still a mystery. Swapped cpu, Agnus and Gary and still getting the black screen. Could it be the crystal? I've never swapped one before nor do I have a 'scope for checking.
 
Well the other cpu actually works and I don't have to lean on it to make the machine work now :)
I expect all the cpu swapping has rubbed some of the crud from the contacts. Once the socket is replaced with a shiny new one courtesy of roy_bates it'll be working fine.

The other board is still a mystery. Swapped cpu, Agnus and Gary and still getting the black screen. Could it be the crystal? I've never swapped one before nor do I have a 'scope for checking.


its possible.

but its best to check if there is any corrosion anywhere on the sockets,under the sockets check the memory.

check everything.

it doesent have to be battery corrosion either,the socket that are used arnt all that good.
i would be checking for loose pins in the sockets bad solder points,really examine the board and components.
it wont take much for it to not work.

you get the idea.

lots of patients is all it takes sometimes combined with a keen eye.
seeing the problem is half the task.and half the way to a solution.
 
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Ok will do. I've had a brief look and it looks clean but I'll really look carefully and check everything.

Sent from my GT-I9300 using Tapatalk
 
Ok will do. I've had a brief look and it looks clean but I'll really look carefully and check everything.

Sent from my GT-I9300 using Tapatalk


take your time.

if you have to split the board into sections,give each area a really good look at close up.
use a magnifying glass,use a torch to shine through the board.
compare pin to pin in the sockets.
if it looks odd,chances are it is.

clean everything one item at a time,including sockets with ipa and a toothbrush etc.
clean the pins in the ic's.

sometimes all this helps.
 
Crystal is possible, but you could also have damaged tracks, eaten away by the acid.
That is very hard to diagnose, but I'm not going that far, usually these boards end up with Amiga-Digital.
If he thinks he can repair them, then they are all his and if not he can use them for parts.

Also because A2000's are quite often sold locally here and they go pretty cheap, as in all parts ordered to save a board probably will be less than buying a complete one.
 
Hybrid

Hybrid

Check the Video hybrid as well (especially the contacts).

And give the thing a good clean with iso-propyl alcohol (must be at least 99% pure).

Also, when you power on, can you hear the ticking of the floppy drive(s)?

If so then see if you can boot something, if you can then it may just be a video problem (most likely the hybrid or Denise chip). It always helps to swap the chips with known good ones as a way of ruling out certain issues.

Finally, look at your power supply, check that the voltages on each wire are correct. (Do this with it plugged into the board so it is under load, you can "backprobe" each pin).

Good luck.
 
PSU is fine - voltages checked and it powers the other A2000 fine.

Traces all appear fine. Actually the corrosion on this board is minimal.

It does not click the drive or boot so something fundamental is wrong.

Now here's the odd thing: it has an 8371 Agnus (not surprising for a board of this vintage) but someone has started to mod for 1Mb chip ram but not finished. Trace J500 has been cut but J102 has not. J101 was in pos 2-3.

I don't know if this is the problem but I'm guessing it would show a green screen rather than black. Anyway I'm betting on Agnus being at fault. Just waiting for a PLCC extractor tool to arrive before swapping.
 
Well, it isn't Agnus. In fact, it appears all the chips are ok so that's something.

I quickly went over all the solder points on the CPU, Agnus and Gary with a soldering iron just to eliminate a dry joint there. No difference.

Going back to the CPU socket I had a good look and there does appear to still be some gunk in the contacts nearest to the battery. I got a very fine screwdriver and gently scraped these contacts and reinserted the CPU. Tried firing her up again and got the black screen then suddenly the display scrambled. This was on composite as it's easier to keep replugging that so I swapped to an RGB cable and what I thought was a white screen was actually an odd-looking very light pink. A switch off and on again and back to black only.

So, I think the next step is to replace the CPU socket with the one Roy sent. I know that's the problem with the other one so I'm in no hurry with that. Will be a day or two as I'm busy with work.
 
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