[Racal] RA-6790 problem

[Robert Nickels]

Hoping someone might have some suggestions about how to revive a 6790 
that suddenly seems to have died.    The only problem I've found is, the 
NiCad backup batteries were both dead, but replacing them has not cured 
the problem.

Symptoms are:  Fault LED is lit,  edge lighting is present, main display 
comes up with all zeros ("00" in the mode display), no response to any 
keypresses and unable to get it to go into BITE mode (AM+Lock).

This receiver was completely overhauled by Gary Wingert 6-7 years ago 
and has worked fine since, with the exception of occasionally "losing 
its mind" i.e. going into Fault, which has always been corrected by 
doing a BITE reset.   According to para. 5.4.1 the above symptoms 
indicade "A6A2 microcomputer assembly is faulty and should be replaced".

Since I don't have a spare A6A2 lying around,  I thought I'd ask here 
for any suggestions, otherwise I'll probably go ahead and try to 
troubleshoot the board - at least to make sure the proper voltages are 
present and the CPU is out of reset and running.

Thanks and 73,
Bob W9RAN.