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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: HeatherK on April 30, 2025, 06:04:52 PM
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Hey everyone!
I finally got around to building one of the ACILL Amiga 4000D PCBs that I bought a few years ago. I was able to source most of the parts new (excluding custom chips and ports) with a few exceptions.
When I turn on the system, I get a completely black screen with an occasional minor change in brightness. The system does not attempt to boot off the floppy drive, so I know it's not getting to the boot process. The processor is a Commodore 040.
Troubleshooting I've done:
- Verified every component is in the correct location, facing the correct direction.
- Checked all solder joints for quality and shorts.
- Ensured R465 is on PCB.
- Tried PSU, processor, ROMs, and RAM from a working system.
When booting the original working A4000D I have, the screen is black when first turned on, then quickly changes to a lighter black (gray) during the startup process. This PCB never changes to the lighter display.
Thanks for any help! ;D
Heather
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Silly questions but just to be on the safe side:
- J100/104 jumpers set to internal for the 040?
- You are using a 2MB Simm for Chip RAM?
- Tried the speed rating to 200ns for the Kickstarts?
- Kickstart ROMs good?
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Further to the suggestions above, J100 and J104 both need to be set to the 'external' clock position (pins 2-3, closest to the 200-pin CPU socket) to operate the A3640 CPU board, not internal.
Diagnosing something like this is a bit more complex because you have many unknowns around possible soldering issues, possible component placement issues, possible defective components. I've no idea if these replica PCBs have been ordered with full testing or not, so an etching fault is another possibility.
To begin with, I wrote some information on debugging low level start-up issues on an A3000 in this recent thread:
https://forum.amiga.org/index.php?topic=77137.msg862992#msg862992
That will quickly tell you what basic aspects of the system are alive or not. The fundamental design of the A4000 is mostly the same as the A3000, so most of the same debugging detail applies. If the CPU is mostly alive and reading ROM data correctly, and without any chip memory SIMM installed, the system should show a bright green screen quickly after power on.
If you can provide another photo showing the jumper locations, it would be worth a quick sanity check of those. Else you can compare them against an existing working board.
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Thank you, everyone. :)
I'll verify all the jumpers and check out the troubleshooting information. I'll reply this weekend as I don't have time during the week. :(
Thanks!
Heather