I encouter two main failure modes. First, the bipolar PROMs degrade at the atomic level, the metal ions in the fuses tend to migrate or 'regrow' over decades, causing bit rot.
Second, the backplanes suffer from mechanical fatigue. After forty years of thermal expansion and structural flexing, especially when inserting boards, the traces and solder joints develop stress cracks. Both are a pain to repair.
Comments
I encouter two main failure modes. First, the bipolar PROMs degrade at the atomic level, the metal ions in the fuses tend to migrate or 'regrow' over decades, causing bit rot. Second, the backplanes suffer from mechanical fatigue. After forty years of thermal expansion and structural flexing, especially when inserting boards, the traces and solder joints develop stress cracks. Both are a pain to repair.
https://retrocmp.com/articles/trying-to-fix-a-dec-pdp-1134-b...
Excellent work.
The feeling of accomplishment when the machine boots after a major repair (almost) makes it all worth while.
(i think i would have found a used backplane...fixing it was crazy clever)