Amiga 500 Rev 6a green screen

[Mark sealey]

Hello all....ok got a A500 6a with a green screen.....yes i know its been coverd quite a few times....But need my own thread so i can follow it more.

Right...If there was battery damage i would know where to start...but there is nothing...really clean A501...and Rev 6a mobo...looked at both sides.

Things done so far

Removed ALL chips and cleaned with PCB cleaner...in Agnus

All legs on chips in Agnus look fine


Ok no Ram chips get warm....agnus gets a little warm afer a bit...cpu gets warm a little...nothing i would worry about.


Seen videos about replacing the PLCC socket....so that might be a option one day.

my next idea is to PIGGYBACK 4 ram chips to see when happens.


Any ideas....?

Thanks all

[cmorley]

If it is light green then isn't that CIA? Have you swapped the CIAs or tried known good CIAs?

[Mark sealey]

Originally Posted by cmorley

If it is light green then isn't that CIA? Have you swapped the CIAs or tried known good CIAs?

Sorry Flashing green.....and Green Screen

[Mark sealey]

also tried another kickstart rom v3.1

[r.cade]

I thought Green screen was bad RAM?

[Mark sealey]

Originally Posted by r.cade

I thought Green screen was bad RAM?

Thats what i hear.... Agnus socket....etc

[Daedalus]

Green screen is when the chip RAM can't be accessed properly. So it could be Agnus, RAM, the various logic chips used on the chip RAM bus, the CPU, the PCB itself... I take it you've tried it without the A501 fitted? It can also be a CIA issue in older machines (swapping them with each other would show if that was the case) if the overlay function isn't working.

A good option might be to fit a DiagROM and use a null modem cable to see what's happening during the boot process. The pattern of failures on the RAM check might help narrow down what's happening.

[Mark sealey]

Originally Posted by Daedalus

Green screen is when the chip RAM can't be accessed properly. So it could be Agnus, RAM, the various logic chips used on the chip RAM bus, the CPU, the PCB itself... I take it you've tried it without the A501 fitted? It can also be a CIA issue in older machines (swapping them with each other would show if that was the case) if the overlay function isn't working.

A good option might be to fit a DiagROM and use a null modem cable to see what's happening during the boot process. The pattern of failures on the RAM check might help narrow down what's happening.

I have a Diagrom but no cable.....is there a "how to" on this method ?

[Daedalus]

There's a bit in the DiagROM readme file, but it's pretty simple. Get a null modem cable (or build one - it only needs gnd, rxd and txd connected), connect it to any computer at the other end (use a cheap USB-serial adaptor if needed), and open a terminal program with these settings: 9600, 8N1. You should then get DiagROM output. It will display what it's checking, and if it finds any failures it will list them. Depending on the machine's condition, it might prompt you to press a key to keep serial communications open - you can use either the Amiga keyboard or the keyboard of the other machine to control it.

[Mark sealey]

Originally Posted by Daedalus

There's a bit in the DiagROM readme file, but it's pretty simple. Get a null modem cable (or build one - it only needs gnd, rxd and txd connected), connect it to any computer at the other end (use a cheap USB-serial adaptor if needed), and open a terminal program with these settings: 9600, 8N1. You should then get DiagROM output. It will display what it's checking, and if it finds any failures it will list them. Depending on the machine's condition, it might prompt you to press a key to keep serial communications open - you can use either the Amiga keyboard or the keyboard of the other machine to control it.

Thank you for the reply.

Diagrom gave me some info....well flashing screens.

Without A501 installed

[ Show youtube player ]

MSG from John Hartwell....

" well uit says ALL bits are bad in memory. so I guess one of tjhe buffers."

with A501 intalled...Finds Fast Ram

[ Show youtube player ]


So i need a Null Modem Cable and USB to RS232/adapter

Thanks all

[Vypr]

Have you checked your PSU?
I have an A500 which was doing something similar except it would work for about 10 to 5 minutesd before displaying hte same symptoms you are getting (both green screen and RAM errors form DiagROM) In my case it looks like the line filter was causing problems as I accidentally shorted 5V to ground and it went up in smoke. Removing it for testing has made the board work properly now so I am assuming the Line filter was introducing some noise on the power lines when it heated up.

Just need to get a new line filter from somewhere as it's probably not a good idea to have it on for any length of time without one.

[Mark sealey]

Ive used my modded pc psu.....I'll try the psu off my A600 Furia.