[Techtoolslist] And another weird test result

[John Robertson]

I don't know if you folks are interested in my headaches, but here is my 
latest one.

Working on an Atari Superman  pinball board. ROM, RAM tests are good, 
board boots, issue is the feature lamps flicker when turned off.

However I am getting something odd on address 1800-18FFh, it displays 
what appears to be the last data bit in the EPROM located at 3800-3FFFh. 
I plugged a different EPROM in and got its last data bit too. What is 
odd is the EPROM, when reading 1800h shows the Address lines all as low, 
but there is the tiniest pulse on /CE(pin 20). I've tried stretching it 
out, but it appears to be the smallest resolution of my Tek 100mhz, 2230 
storage scope - which I am still learning how to use.

At this point I figure it is a timing issue so will dig further, but I 
just thought is was most curious that it didn't matter which address 
location 1800-18FFh was chosen, I got what appears to be the last byte 
in the EPROM! I have no explanation on how that can happen. I will now 
test that by burning a couple of  2716 with only the last byte set, will 
try AA and 55 and see what happens...

John :-#)#

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