A3640 problem & A4000 questions

[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!

[Firedawg]

Sorry to have rekindled this thread again, but I have uncovered the same problem with my A3640 Rev. 3.1 board.  I have followed this thread as wells as the article written by James Jackson on this very subject, but I have a couple of questions I would like to cast out to the techies.  1) Can I use the radial versions of the capacitors 22uf 16volts, or must I use the SMT versions?  2) Can I use a higher voltage like Jame Jackson eluded to in his article(i.e. 22uf 25volts)?    I have removed all the caps C106(leaked), C105(leaked), C107(leaked), C102B(it appeared to have leaked), C102E (Did not leak, but removed just the same).  Before proceeding with my Cap removal I tested with a good A4000 mobo and memory, all I was getting was a purple screen with the hard drive light constantly lit.  Then tested mobo with A3600 '030/25 CPU card and booted right up.  So, that is what isolated my attention to the A3640 and the Cap problem.  Thanks for any help....

Follow-up.................................

Thanks for the information.  It was most helpful.  My questions were not directly answered, but the links provided  were very helpful.  Thanks, Mike.

[amiga92570]

http://amiga.serveftp.net/A4000_HardwareGuide/main.html

[Zac67]

Just for completeness: NEARLY ALL A3640 have three electrolytic capacitors reversed (only the very latest batch was corrected): C105, 106, 107. The silk print is wrong, use a simple multimeter to verify. Sometimes the caps just dry up and that's it, but often they leak and damage the board.

http://joj.home.texas.net/amiga/amiga03.html
BBoAH

[TjLaZer]

OK dumb question, how can I tell if they are on backwards?  I guess a simple pic of the board with them on correctly will show that too.

On mine C105, C106 and C107 has the blue side of the cap away from +.  

Example:  With CPU board oriented with CPU at top left, C106 has blue side of cap to left of board.

EDIT

On another board I see the caps are indeed in wrong in relation to silk screening!  So now I am left wondering which board is correct!!! LOL

EDIT V2

You can verify this by locating position U103, just below the oscillator. Vcc (5V) and G(nd) should be printed on the device. Check using an ohm meter for a connection between VCC and the black side of the capactors, similarly check for a connection from G to the other side of the capacitors.

http://amiga.serveftp.net/A3640_capacitor.html

[Zac67]

The silk screening is always wrong for these caps - it wasn't changed when the error was discovered. Just use a multimeter, set it to low Ohms/beep and check whether the cathode (-) is connected to GND (like on the other capacitors) - or rather the anode (+)...

[TjLaZer]

OK thanks, so if the 3 caps appear to be in wrong you most likely have a good board!  Hahaha