Advice on fixing an Amiga 500+

Tool suggestions, soldering tips, general useful electronics knowhow.
Post Reply
Steve
Posts: 253
Joined: Fri Sep 15, 2017 11:49 am

Advice on fixing an Amiga 500+

Post by Steve » Wed May 15, 2019 9:49 am

Hi guys,

Symptoms: red then green screen
Solved red screen by replacing the ROM.
New symptom: just pure green screen.

I'm new to Amigas in general and I'm trying to repair an a500+. It had a small amount of battery leakage, I removed the battery and cleaned up the board. The small gate array IC in the data path was corroded so I replaced it with a new socketed version. I checked all traces and everything was good around the leakage. All traces to Gary are good, and to the IC I replaced.

I got a spare 256k ram chip and bridged it on top of each motherboard ram chip in succession to see if one was faulty, no change still green screen every time.

I cleaned and reseated every single socketed chip.

I swapped out every custom chip from a known working a500 motherboard, but could not swap Angus as she's an incompatible model since this board is a plus variety.

I'm seeung if I can source a new Angus in the mean time.

Any other ideas?

Thx
Falcon ct60e 060 - 256mb ram - phantom bus and dsp accel // Atari TT - Thunder and Storm IDE 64mb ram - Lightning VME - USB LAN - Ati Mach64 2mb // Atari STM 4160 - 4MB ram - 16Mhz exxos 1.5 booster - Ultrasatan

Maximilian
Posts: 67
Joined: Thu Feb 28, 2019 5:02 pm

Re: Advice on fixing an Amiga 500+

Post by Maximilian » Wed May 15, 2019 8:16 pm

Well, Green is a problem with Chipram normally, how many times does the power led blink?

Did you replace the kickstart with exactly the same chip?

Personally i would check:
1. The pcb again with the help of http://www.amigapcb.org/
2. Using Diagrom
3. The Agnus socket

Piggybacking ram will only work if pins are open after a failure, and if a bit is shorted to GND or VCC it will not help.

Maximilian
Posts: 67
Joined: Thu Feb 28, 2019 5:02 pm

Re: Advice on fixing an Amiga 500+

Post by Maximilian » Wed May 15, 2019 10:22 pm

Maximilian wrote:
Wed May 15, 2019 8:16 pm
how many times does the power led blink?
Disregard that, was thinking of another machine :-)

Did you swap the Cia's?, there is a OVL line that can cause green screen problems..

Steve
Posts: 253
Joined: Fri Sep 15, 2017 11:49 am

Re: Advice on fixing an Amiga 500+

Post by Steve » Thu May 16, 2019 1:05 pm

I replaced the kick start with a 1.2 one from my spare a500. I did try swapping the Cias, no change. I'll check that website you posted.
Falcon ct60e 060 - 256mb ram - phantom bus and dsp accel // Atari TT - Thunder and Storm IDE 64mb ram - Lightning VME - USB LAN - Ati Mach64 2mb // Atari STM 4160 - 4MB ram - 16Mhz exxos 1.5 booster - Ultrasatan

Maximilian
Posts: 67
Joined: Thu Feb 28, 2019 5:02 pm

Re: Advice on fixing an Amiga 500+

Post by Maximilian » Thu May 16, 2019 4:51 pm

Ok, make sure you have 1mb of ram installed as a max as KS 1.2 does not support 2MB chip if I remember correctly.
(No mem expansion inserted)

Did you try(with the correct extractor tool) to extract the Agnus and inspect it's socket?, sometimes just taking it out and putting it back is enough.

I have a creepy feeling that there is still something wrong around the battery damage, check the previously mentioned site.

Post Reply