Tandy 1000 - Memory fault on boot

[nullvalue]

I am booting a newly acquired Tandy 1000 (which sat in a garage for the past few decades). This is the very first Tandy 1000 - not a 1000A. When I turned it on I got a memory error. It was pretty dusty and nasty inside so I washed the motherboard and the whole thing out - looks like new now. I took the opportunity to reseat all the IC's on the motherboard - put it back together and still getting the same message.

Error message is:

vid addr:   base:    bbe8h  off: 0082h
data fault: written: ffffh read: FFDFh

I can get different messages by swapping the "FUD8452" chips around on the motherboard - but I don't have any spares and am kind of unsure how to determine which are actually the bad one(s). What would be a good replacement for these?

EDIT: The service manual indicates these are 64K DRAM 150ns. There are 16 of them.

 

[nullvalue]

I had a 256K memory expansion board for this machine which turns out also has 64K DRAM chips on it - and was able to play the swapping game until I found that I actually had 2 bad chips.. Guess I have to order a couple to get this machine back up to 384k!

 

[alank2]

Good job figuring it out and getting it working!