A3640 problem & A4000 questions

[Olecranon]

Hi Everyone,

I just purchased my first A4000 system and it looks like it's going to be a nice machine.  The system currently has an A3630 CPU card installed.  The person I purchased it from gave me an A3640 board and a couple extra A3630 boards that he said he couldn't get to work.  I was able to get the two A3630 boards running, but not the A3640 board.

Does anyone have any suggestion?  I set the jumpers on the A4000D motherboard from INT to EXT for the clock, but that made no difference.  I believe all the jumpers on the A3640 are closed and its set to maprom enable.  Oh, it's a version 3.1 of the card.

A couple other questions.

System has 3.0 in ROM.  Can I run WB3.1, WB3.5, or WB3.9 with KS3.0 or do I need to upgrade to the 3.1 ROM?

Thanks for any suggestions.

[Olecranon]

After some examination of the board, I'm starting to wonder if 3 out of the 5 capacitors are shot.  I used to be a PC Computer tech and saw lots of boards with bad capacitors.  Usually the caps would be bulging with electrolyte leaking from the top.  These dont look like that, but the metal contacts look corroded.  Two of the five look fine.

I let the A4000 sit a black screen for awhile and the 040 chip never increased in temperature.

Has anyone done a capacitor swap on one of these cards?

I found some good info here, but it would be nice to talk to someone who has done it.

http://joj.home.texas.net/amiga/amiga00.html

[Olecranon]

Jeff wrote:
Some A3640's also had some caps installed backwards at the factory. I have at least one rev 3.1 like that. Sometimes replacing the small surface mount capacitors can bring them back to life.

Good Luck,
Jeff

Ok, looks like we might be on to something here.  The instructions I have state that I need 22uF 16V leaded radial capacitors.  Anyone know if I can pick something like that up at radio shack  :-)

I might go ahead and give it a shot.  My soldering skills are above average, hehe

[Olecranon]

Matt_H wrote:
3 of the 5 capacitors on the 3640 have the polarity reversed because the silkscreening on the PCB is wrong - those are probably your bad ones.

I started a thread on this last month - there might be some good details and links in there as well.

I didn't trust my soldering skills, so I had Amiga Center correct it for me. Still waiting on the postal service to deliver the thing, though!

How much did the repair cost you Matt?

[Olecranon]

amiga92570 wrote:
https://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=193009&pa=193009PS

Thanks for that link.  I'm not really should how I would solder that.  I haven't worked with surface mount caps before.  I'm thinking I might just get a few trusty ole radial style ones and bend/cut the leads.  

[Olecranon]

I received a quote from Amiga Center that repairs would not exceed 70E (about $91 USD), but I can send it in for a free diagnostic.  I would guess that capacitor replacement would be fairly cheap?  

Then I probably need to add shipping to/from France on top of that (not sure how much that is).  I only paid $150 for computer, so I hate to spend another $150 just to get the 040 up and running.  I'm also a little concerned about trying to purchase another one of these with the problem being so widespread.

Any suggestion?  I've never dealt with Amiga Center before.  Should I attempt the repair myself, then send it in if I fail?

[Olecranon]

***UPDATE***

I managed to repair the card myself  :-D

I went to the local Radio Shack and purchased three 22uF capacitors and set out to get the board running.  The first problem I ran into was breaking one of the solder pads off the board while removing the bad capacitors.  I managed to get a small piece of wire connected to the spot where that pad connected and then get the capacitor installed.

After replacing the three bad capacitors, I tested out the board.  Still no system boot.  Then I noticed a circuit trace had been eaten away by one of the leaking caps.  I scraped the coating off the trace where it was broken and connected them with some solder.  Bingo..  Machine started up just fine, hehe.

It's not the prettiest job I've ever done but it works!