Amiga 500 yellow screen

[DetFedeSvin]

I have an Amiga 500, Rev 6A, with yellow screen. I have tested all the custom chips, the CPU, u10, u11, u12, u13, u34, 35, and the ram chips in another A500 where they are working without any issues. Furthermore, I have swapped the custom chips’ single sided sockets for machined sockets. All the CPU’s lines is checked.

When removing a ram chip, the screen changes to green.


When swapping the Kickstart rom to DiagROM, the check halts when checking the raster.


DiagROM serial output:


Amiga DiagROM V1.2 - 13-Aug-19 - By John (Chucky/The Gang) Hertell


Testing if serial loopbackadapter is installed: <> NOT DETECTED
- Parallel Code $ff - Start of ROM, CPU Seems somewhat alive
Checking status of mousebuttons for different startups:

Set all Interrupt enablebits (INTENA $dff09a) to Disabled: Done
Set all Interrupt requestbits (INTREQ $dff09c) to Disabled: Done
Set all DMA enablebits (DMACON $dff096) to Disabled: Done

Testing if OVL is working: OK
- Parallel Code $fe - Test UDS/LDS line
- Test of writing word $FFFF to $400 OK
- Test of writing word $00FF to $400 OK
- Test of writing word $FF00 to $400 OK
- Test of writing word $0000 to $400 OK
- Test of writing byte (even) $ff to $400 OK
- Test of writing byte (odd) $ff to $401 OK
- Parallel Code $fd - Start of chipmemdetection

Addr $00080400 OK Number of 32K blocks found: $10
Chipmem Shadowram detected, guess there is no more chipmem, stopping here

Startaddr: $00000400 Endaddr: $0007FFFF
- Fastmemcheck skipped as we found chipmem
- Parallel Code $fb - Memorydetection done

Using $0006CCEC as start of workmem (Base)

- Parallel Code $fa - Starting to use detected memory

Testing if serial loopbackadapter is installed: <> NOT DETECTED
Detecting if we have a working raster: rr11m 2;11H?? 2;11H





Any ideas on where to look next?

[nogginthenog]

Adrian's Digital Basement released this video recently.

Green screen, but similar problems. DiagROM passed the memory test but failed on the working raster check.

It turned out to be the RAM.

[ Show youtube player ]

[DetFedeSvin]

Could be the ram, however I have checked all the custom and ram chips in another Amiga. Where they are working. Can it be a passive component?

[DetFedeSvin]

Unfortunately the there are no change if a keyboard or a memory expansion are connected/removed.