A500 Green screen or ‘Curse you, Fat Agnus!’

[GoodCrossing]

Hi,

I recently bought an Amiga 500 which was fully functional that I wanted to use for testing out some old games and also to help repair an Amiga 2000 I also warned. I replaced all the chips from the Amiga 2000 in to the working a 500 board in order to test them out. My suspected culprit for the Amiga 2000 not working was Fat Agnus.

I stopped all the chips one by one and tested the computer at each step. However when I replaced fat Agnus, I got a green screen. I was quite happy, as I finally found the fault with the Amiga 2000, unfortunately, when I replaced the working fat Agnus into the Amiga500, I still got the same green screen.

So I have two non-functioning Amigas. I want to fix my 500 quickly, so that I can get back to fixing the original 2000 that was faulty. I have a couple of questions:

A green screen usually indicates a problem with the RAM. I have a RAM expansion board for the omega 2000 with some socketed chips. However they are slightly different from the ones that I have in the omega 500. Does this work?

A green screen usually indicates a problem with the RAM. I have a RAM expansion board for the Amiga 2000 with some socketed chips. However there are slightly different from the ones that I have in the omega 500. Does this work?

The power light Has 10 short flashes, and one long flash. I’ve seen this indicates a problem with the Agnes cheap. Could it be that I have broken the socket? Unfortunately I don’t have a removal tool, so I do used A flat head screwdriver.

finally, if it is not the socket, and the chips in the expansion board are not suitable for the a 500, would diagrom help find out which of the chips is faulty? I don’t have it but I can buy it, and, with the prices that I’ve seen for the RAM chips, replacing them all would be too expensive.

Sorry for the grammar in this thread, currently dictating via voice. So yes, omega means Amiga :P

EDIT: Forgot to mention. The chips in the expansion board are 41256AP-12

[dalek]

Probably a flakey Agnus socket on the A500. I would get a pin and gently pull out each pin in the socket so that it has a bit more tension when the chip is seated. And try some contact cleaner on the socket pins and Agnus chip pins. If that helps it indicates your socket is worn.


That or in the process of swapping Agnus chips some of your chip RAM died (e.g. killed by static) - in which case diagrom is your friend to find the faulty chip(s).

[GoodCrossing]

Fixed! Had to laboriously get Fat Agnus in the exact right position but it's worked. The socket was a bit damaged I'm assuming from me removing the chips without the proper tool. In fact, I also tried to get the A2000 Fat Agnus in the A500 again and reseated it many times as I did with the A500 chip, and eventually, I got a screen asking for a floppy.

Both chips are working then! Closed the case and called it a day.

[r.cade]

Once the socket is bad, and they were mostly bad from the factory, it will randomly get green screen at boot and crash.

You can replace the socket, but it's no an amateur-level job. You really need a vacuum desoldering tool and good technique. Once you replace it, the computer will work perfectly.

[GoodCrossing]

Yea. I've hopefully got the chip in a good enough position that it won't lose contact randomly. It's amazing how fragile these sockets are then; the issue started after the very first time Agnus was removed (I'm sure it hadn't been removed before as I broke the warranty seal myself)

You can replace the socket, but it's no an amateur-level job. You really need a vacuum desoldering tool and good technique. Once you replace it, the computer will work perfectly.

Actually, I replaced a Fat Agnus socket on an A2000 yesterday (just in case that was faulty too, after seeing the situation on the A500) and I found it laborious but not too difficult. I used a Hakko 888D and a standard solder sucker (the kind where there's a spring-loaded plunger) and I carefully desoldered each pin. I then went one by one verifying all pins were free (using tweezers or a small screwdriver I could slightly wiggle them). Some were a bit stuck but a very careful and soft push with the screwdriver set them free. Then I pried up on the socket using a thin blade (an iFixit Jimmy) and it lifted up. Two pins remained soldered to the board but heating them up while slowly pulling with tweezers did the trick. Unfortunately I lifted a pad in the desoldering stage but it wasn't too bad; quite an easy one to fix.