Amiga 4000 PCB build - yellow screen without chip ram

PacificState

Member
AmiBayer
Joined
Apr 17, 2018
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82
Country
USA
Region
CA
I'm rebuilding my old A4000 motherboard (which was battery rotted) by transplanting components over to a new clone PCB. So far I've followed Chucky's guide at http://wordpress.hertell.nu/?p=1053 all the way to the point of installing components to enable Fast RAM (I was waiting for my serial adapter to arrive) - but there's no serial output and I get a yellow screen *without* any Chip RAM installed.

I have the latest diag ROMs installed along with an A3640 - however, I'm not totally sure that every component was in working order before the build, given that there was fairly localized but hard to repair battery rot. Given the instructions, I'm also still missing a lot of components including Buster - although the guide indicates this is totally fine.

I'm guessing that this is a CPU exception really early at boot, so my next inclination is to buzz out the buses. In the meantime, the soldering looks fine and the chips are the right way around - any suggestions as to what I could do next, though?
 
The fastest way to solve any problem is to post for help - it's now booting successfully to the DiagROM menu. I'm pretty sure the problem was resolved ultimately by going back and resoldering one of the GALs, but there were also a couple of tiny bridges to fix en route.
 
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