Amiga.org

Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: djkoelkast on June 11, 2011, 09:33:17 AM

Title: Another A2000 mainboard: some questions
Post by: djkoelkast on June 11, 2011, 09:33:17 AM

The A2000 I bought had a mainboard I couldn't get to run. As I found a working mainboard for absolutely no money (paid € 3.50) I thought I'd had a shot at an easier repair, or have some spare.
This mainboard should work, but crashes a lot, is what I understood. It has some battery damage, but mainly on the back side and it isn't that bad as the 1st one.
Also there is a whole chip missing! I hope you can help me out:

1: Overall
(http://i.imgur.com/shs6I.jpg)

2: Why are these pins bent to make it jumpered (apart from: they had no jumper, why is this jumpered and should it be?) It's J500. (found this one: J500 This jumper is used to enable the 512k of RAM at $C00000 and the real-time clock. It is normally closed; opening it will disable both this extra RAM and the real-time clock. ) I'll find me a normal jumper then ;)
(http://i.imgur.com/rYepj.jpg)

3: Why is this? I mean the resistor with the small round brown thing soldered to it. I have no clue what it is. Also J901 has a jumper on it that doesn't quite fit. Does it belong there? Why should one jumper J901?
(http://i.imgur.com/vMbSF.jpg)

4: What chip is missing and why? (besides that: how can it even work without it?)
(http://i.imgur.com/8hA3C.jpg)

The rest is for the battery damage:

(http://i.imgur.com/TKQ0x.jpg)

(http://i.imgur.com/QYnwo.jpg)

(http://i.imgur.com/xpYHI.jpg)

Any help / clues would be greatly appriciated.

Title: Re: Another A2000 mainboard: some questions
Post by: lunithy on June 11, 2011, 10:13:20 AM

I hope these pics help? the first one is the of the chip that's missing
  (http://i623.photobucket.com/albums/tt316/lunithy/DSC01705.jpg) (http://i623.photobucket.com/albums/tt316/lunithy/DSC01706.jpg)(http://i623.photobucket.com/albums/tt316/lunithy/DSC01709.jpg)

Title: Re: Another A2000 mainboard: some questions
Post by: djkoelkast on June 11, 2011, 10:22:56 AM

It already has a 5712 chip, so it needs 2?

Title: Re: Another A2000 mainboard: some questions
Post by: lunithy on June 11, 2011, 10:31:35 AM

Oh mine is 2000HD so not sure

Title: Re: Another A2000 mainboard: some questions
Post by: djkoelkast on June 11, 2011, 10:41:26 AM

For what I found the missing chip is a Buster chip and it should be able to put just any Buster chip in it. I do have one on my old mainboard I guess.

On my old mainboard I have a Buster 5731 Rev A 318075-02 on this very spot.
I also found out this new mainboard has KS 2.04 (I also have a 1.3 and 1.2 chip here)

What if I don't have a Buster chip? Does it cause problems?

Title: Re: Another A2000 mainboard: some questions
Post by: djkoelkast on June 11, 2011, 11:56:54 AM

Just popped the thing over and it works.
1.2, 1.3 and 2.04 are all working, hdd controller is working (with a whopping 40MB scsi harddisk), 1MB chipmem. All looks fine.

So which way to go now. Use 1.3 or 2.04? (it has a kickstart switch, but that doesn't work) or get me a new kickstart switch.