Amiga A4000T component ID help please

[Jeff]

Hello,

I just received my A4000T motherboard from an auction and I need to replace a damaged component at location CE760A. It looks like it may be a capacitor and it is near the edge of the motherboard between the Zorro and Video slots. It's is visible in the motherboard photos on both of the Amiga Hardware sites.

It looks like it may have been damaged by the insertion of a card. It's markings include 22 and 16v. I will need to find a suitable substitute part as I'm sure I won't find another exactly the same.

Hopefully this is why the right mouse button doesn't work also:-).

Thank You
Jeff

[Matt_H]

The schematics on this page might help.

[Jeff]

Well I have those and I tried that. Unfortunately the A4000T scans are so poor I can't locate that part on them.

Does anyone know of better scans of the A4KT schematics than those? Or perhaps someone has the service manual?

Thank You

[Doobrey]

Jeff wrote:
Well I have those and I tried that. Unfortunately the A4000T scans are so poor I can't locate that part on them.

Gimme a gold star, I found it..
The archive has misnamed the ISA slot schematics as A4000T-IDESlots.jpg.
Anyway, on that pic, bottom left. It's a 22uF 16v electrolytic capacitor.

Bad new is, it has nothing to do with the mouse buttons  :-(

[Jeff]

Great! Thank you.

I didn't think it would cure that, but I want to replace it anyway since it's creamed. I have a dead A3640 that has about 4 of those same caps so I found the part already :-D.

I'll keep up with the schematics and try to fix the RMB also. I fixed this same problem years ago on an A2000 but I can't remember what is was.  Perhaps a SMD fuse on this one? I'm off to get some equipment from storage :-).

Thank You again

Jeff

[Matt_H]

Glad you found what you needed. Hope your repairs are successful!

[Doobrey]

Silly question, but have you checked the right button works on another amiga (or with a multimeter between pins 4 and 9 on the mouse plug)?

It's possible one of the 68 ohm resistors in front of the IO module connector has blown.  Can't say which one, cos they aren't marked on the silkscreen or the schematics :pissed: , but checking with a meter should show up continuity between pin 10 of the CIA U550 and one end of the resistor.

 Other than that, it could be the CIA gone bad.. Is the floppy and parallel port working OK?

[amiga4001]

Try reseating of the modules on which the keyboard connects to.
I once owned a A4000T and once in a while I had your problem of a non working RMB.
After reseating of this print on it's connector it all worked again.

[Zac67]

Forget those electrolytic caps on your A3640 - three of them are mis-polarized and probably long defunct. You can get new ones for a few cents at your favourite electronics shop.

[Jeff]

You are correct, the caps on the 3640 are backwards :-). I just got the machine running today!

Here is what I started with if you want a look;
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4598&item=5235235258
The seller also included the I/O port, Audio/Video, and Disk I/O boards, Sweet!

However, I had a few problems.

1) The right mouse button wasn't working. I traced it to a fried trace on the I/O port board. I don't even want to know how that happened, but thank god the CIA's are good:-D

2) They had 40.68 desktop Roms installed on the board for some reason, so I had to fix that. The machine doesn't seem to like bootable devices on the IDE buss with the 40.70 roms installed. This was not problem with 40.68, but the onboard SCSI was disabled.

3) That cap was mowed off, but that was an easy fix.

Today I got it all running in a HUGE UGLY yellowed old AT server tower I had slated for scrap. The config is A4000T MB, CS MKIII 060 with 128 megs, VT4000, Picasso IV, (2) 4.3 Gig UW SCSI drives, Sony CDRW on the IDE Buss.

Now I need to find a nice looking AT tower and so I can clean it all up and make it look nice.