i just turned six non-working a-series cameras into three functioning ones. a little diy goes a long way. i am no camera tech but with a syringe, some watch oil and some light seals you would be surprised what a few hours can achieve. i now have 2 working black ae-1 programs and an a-1 (i already use a new f-1 and a chrome ae-1p) that will provide me with some cash to buy other things i will use (like film and strobe gels).
if the cameras worked would you still want a different one? if so just do it and get the new f-1. the t90 is good for the metering but its plastic body doesn't feel as good as the f-1. when you can be bothered fix the old ones and sell them to someone who would love them. i have had these cameras for 4 years or more waiting for me to fix them and i finally did it and if i can, anyone can.