I will attempt to resolder, and report back. The solder pins are relatively large and should be no problem.
Darn

I did resolder the sockets, and unfortunately the same symptoms. I did recheck, all the solder joins and they did look ok.
It is possible that the buffer caps, next to the memory sockets are bad. These are not electrolytic and should not be prone to leaking however, it fits the symptoms. Has anyone ever seen these go bad?
Hi Motor,
Did the A3000D boot up properly before you started adding RAM? Or did it go to a yellow screen for no apparent reason one day?
I assume the 8 20-pin DIP sockets (U850D-U857D) are empty and that the 8 ZIP sockets at U850-U857 have the 1Mx4 ZIPs? Both these groups are considered Bank 0 and you won't be able to power up properly if they're both populated. Also, it is important that one does not mix ZIP RAM densities.
You also have to populate the following banks in sequence, starting from Bank 0 or it won't work:
Bank 0 (8 ZIPs) U850-U857
Bank 1 (8 ZIPs) U858-U865
Bank 2 (8 ZIPs) U866-U873
Bank 3 (8 ZIPs) U874-U881
This might be of further use to you (A3000D User Manual, quite detailed for a "User" manual):
http://oldcomputers.net/Amiga_3000_manual.pdf
@MinTerm,
Thanks for the reply, this did happen when adding memory, This particular A3000 was on the shelf for a while and had 8 megs in it.
Your advise about the memory banks is good one, however in this particular case is not the problem. I know about the screwy zip bank configuration of the A3000, but it still was a great question to ask.
Also as for the memory, it is all 60ns page mode. No issues here mixing static and page mode, or speeds.