[Techtoolslist] 8T28 Data buffers can mask RAM test faults...

[John Robertson]

I was servicing a Williams System 4 pinball MPU the otehr day and while 
my 6800 pod said there was a Bit 1 problem with the Long RAM test, it 
turned out that there was no problem with the Data 1 line. However I did 
have a small solder bridge between D3 & D4 which I only found by using 
the Williams test fixture BUS test module where it showed that D3 & D4 
(buffered) where operating together.

So, something to watch out for - buffered Data lines may not show up on 
the pod tests if there are shorts or other problems. At least with the 
8T28 bi-directional buffer!

John :-#(#
-- 
How to subscribe or unsubscribe from TTL 
http://seven.pairlist.net/mailman/listinfo/techtoolslist