Amiga 2000 resurrection - 2 faulty boards

[JHawk]

Hi,

I have been trying to get an A2000 working again for some time. My original board (rev 6.2), which I'd had for 8 years before it started developing RAM problems, had a broken Agnus socket which I discovered under a 2MB chip ram upgrade - there was a wire joining a broken connector on the upgrade directly to the board. I tried to remove the socket using hot air, but some of the metal rings on the board got pulled a bit far, and the board looks a bit scorched. I think the damage may not be too bad, but I haven't put another socket in yet as by this time I had bought another board.

This one (rev 6.0) had some battery leakage and was giving a white screen. I gave it a cleanup and replaced the 68000 socket, but the white screen remains. The screen appears to be white from the moment the power is switched on, rather than going through the usual checks.

So I got another board (rev 6.4). This took some persuasion to work (a lot of chip swapping/reseating) but did eventually start and I loaded workbench from floppy. But when I came to putting my 2060 back in, it started behaving strangely again. I quickly removed the CPU card. It either boots to a corrupt workbench prompt, or powers itself down after a while. The disk drive clicks, but can click several times before the workbench prompt appears.

I thought the PSU may be the culprit, but the voltages all seem ok. I even got an ATX adaptor, but that does the same thing. I thought of socketing the RAM (in both boards) but haven't got round to it yet. It wouldn't be the cause of the powering down anyway.

Any ideas what else I could try? Could some capacitors be failing?

Thanks in advance,

John

 

[Merlin]

It definitely sounds like some failing caps to me. Have a close look at them and look for ones with domed tops, where they appear to be more 'opened' than the others; these will be the ones that failed.

To be honest, it's probably better in the long run to replace the lot; kits of capacitors can be obtained from one of the members on here (Cosmos).

https://www.amibay.com/showthread.php?t=4400

 

[JHawk]

I can't see any that are bulging, but I've asked Cosmos for some cap sets anyway.

Thanks,

John

 

[Justin]

another thing to look for are dull/discoloured solder pads (caps don't always bulge)

 

[chiark]

(caps don't always bugle)

Every bugler I've seen has headgear of one form or another...?

Caps or bad connection somewhere along the line. Both are not terribly simple to debug

 

[JHawk]

My caps arrived today from Cosmos. Coincidentally, I recently acquired a rev 6b A500 with a similar distorted kickstart prompt screen, so I started by recapping that one. The kickstart screen is now displayed properly, and the slightly unstable video is corrected.

I then tried recapping the rev 6.0 A2000, but there's no change at all - it still goes straight to the white screen, without going through grey first. I wasn't really expecting the caps change to fix this, but thought I should do this one before the (more likely to work) 6.4. There's still some battery leakage damage on the CPU slot and I was wondering if that might be a problem. No pins are shorted though. If I revived this machine, I would want to switch this CPU slot for the one in the 6.2. I managed to remove an ISA slot a while back just to see if I could, so changing the CPU slot shouldn't be much harder, just a few more pins.

I'll try the rev 6.4 A2000 tomorrow - I have my fingers crossed for that one.

 

[r0jaws]

Good luck, and remember, pictures are always welcome.

 

[JHawk]

Some good news: After recapping the 6.4, it boots to an uncorrupted workbench prompt, and the power stays on. I've loaded Workbench from a floppy and that worked fine.

Not so good news: I still can't get the Blizzard 2060 to work with it. I think I was getting the same thing before the recapping - it shows the rainbow colours for a fraction of a second, the Amiga goes through the grey/bright white screens, and then it just stays on the white screen. Holding the mouse buttons down has no effect. Unfortunately with only one working A2000 and one CPU card, I can't tell whether it's the Amiga or the 2060. The 2060 did seem to work fine when my first A2000 was dying though.

I've swapped the busters with one from another board, but no change.

I found a nice burn on the 2060 card at the jumper for SCSI termination power - a capacitor has been burned clean off the board. I don't think this is the problem as I have photographic evidence it was like that when the board was working, although I don't recall noticing it before today. There was a nasty smell the first time I turned the A2000 on after it was delivered (2002), which I always thought was because I'd put a VGA cable in the wrong place (between the Picasso II and 486 bridgeboard I think) but perhaps it was the 2060 burning instead.

I've tried swapping memory around in the 2060, but with no change. There are jumpers for configuring SCSI, but I don't think they could be preventing the machine from booting (there's no HD connected at the moment).

Any suggestions?

Will post some pictures later.

John

 

[matt020]

Hi. Any updates to this?

 

[JHawk]

Hi. Any updates to this?

I tried an ordinary Zorro II board in the 6.4 A2000, a GVP HC8+, and it was recognised fine, so the Zorro slots seem to be working. I still can't tell whether the 2060 is at fault or if it's the CPU card since I only have the one accelerator and still only one working A2000.

I haven't got much further with the 6.0 board. I put a different kickstart in a while ago (although I can't remember the details - should try again) and that gave a black screen rather than the previous white. It was still appearing immediately though. I also removed the RAM chips to test them, although I didn't think the main fault is the RAM, and they all seem fine.

And now the promised photos:

The video fault on the 6.4 A2000, fixed by recapping.



Recapped 6.4 board. I haven't done the axial caps near beside the Zorro slots yet.



Closeup



Working 6.4 board.



Recapped 6.0 board.



Closeup showing battery damage to CPU slot.



The Rev 6 A500 which showed similar video fault to the 6.4 A2000 after recapping. Only partially done in the photo - I started with the big ones and worked down - but was working again at this point.

 

[JHawk]

Tried the 6.4 A2000 with the 2060 today and a 3.1 kickstart rather than the 2.0 it had previously.

Still no joy. It's going through the following sequence:

Black screen
Rainbow colours
Black screen
Grey screen
Flicker
Grey screen

Booting without the 2060 is the same sequence without the rainbow colours and then progressing to the workbench prompt. My post above says I was getting a white screen previously, but that might just be the different kickstart version.

On the 6.0 machine, I've found a damaged track just under the bottom of the CPU and joined it with a piece of wire. It still has no RAM, but it's giving the same instantly white screen.

I'll try putting the RAM back in tomorrow, but what should an Amiga with no RAM be doing? Shouldn't it give a coloured (yellow) screen, and not immediately? There may still be another fault.

John

 

[Merlin]

I'd check this Wiki entry that ClassicAmiga has that covers all error colors, beeps etc.

http://wiki.classicamiga.com/Amiga_boot_error_code_colours

No RAM present or a RAM error should trigger a green screen.

 

[JHawk]

Thanks Merlin.

I think I've spent long enough on the 6.0 board. Since at least one track has been damaged by the battery acid, there may be others since quite a few areas of the board were affected.

I gave the 6.2 board (damage to the Agnus socket area) a last chance today by fitting a new socket using wire where I couldn't get a connection onto the board. It was booting to the workbench screen for a while but giving the same behaviour with the 2060 as the 6.4 board. It has now stopped working, just sits there with a black screen, and I have been unable to revive it so it's going on the scrap pile with the 6.0. The repair to the Agnus socket was always going to be fragile and I was pleased just to see it work at all.

So it looks likely that I have a fully working 6.4 A2000 but a dead 2060. The 2060 is the main reason I used the A2000 and I'd really like to get it working again. Does anybody on here repair them or know of anyone who does?

Thanks,

John