Soooo many failed devices. This reminds me a bit of curiousMarc's battle to restore the HP9825 that got over-volted. I think that was over 20+ TTLs he had to hunt down across all the boards.
Jerry, when you mention the custom devices, are they "programmed" by being "burned" with the custom "code" at the IC factory or are they completely custom ICs with no "code" in them, i.e., basically custom layout of transistors, etc., to perform custom functions? Theoretically, might someone with unlimited time be able to do some kinds of tests on the failed custom devices to figure out what they actually do? This is a fascinating series!
Some of the fuse and mask programmable logic ICs (PALs, GALs, etc.) were 'simple' enough that one could exercise them thoroughly enough to determine the function and likely original fuse settings. As they added more internal latches the number of permutations will increase to a point that it is like trying to reverse engineer a random seed generator if they were made to do something like that.
Yes I was thinking the same thing. Oddly I have two to repair and they both have a similar number of faults. I assume that they may have been fitted into machines which had PSU faults.
Soooo many failed devices. This reminds me a bit of curiousMarc's battle to restore the HP9825 that got over-volted. I think that was over 20+ TTLs he had to hunt down across all the boards.
The 9830A I showed a few years ago had over 100 failed IC's but not so many on a single board.
"...Other than boards with one device on them..." LOL
Jerry, when you mention the custom devices, are they "programmed" by being "burned" with the custom "code" at the IC factory or are they completely custom ICs with no "code" in them, i.e., basically custom layout of transistors, etc., to perform custom functions? Theoretically, might someone with unlimited time be able to do some kinds of tests on the failed custom devices to figure out what they actually do?
This is a fascinating series!
Some of the fuse and mask programmable logic ICs (PALs, GALs, etc.) were 'simple' enough that one could exercise them thoroughly enough to determine the function and likely original fuse settings. As they added more internal latches the number of permutations will increase to a point that it is like trying to reverse engineer a random seed generator if they were made to do something like that.
Yeeesh. Was this stored in the microwave? What a pain!
Yes I was thinking the same thing. Oddly I have two to repair and they both have a similar number of faults. I assume that they may have been fitted into machines which had PSU faults.
Promo'SM