... and it's a two-fer of appreciation, with Bill Dromgoole's report on how the Univac repairs "get done". Some of the failures you describe - gradual loss of function across cards - suggests to me general problems like power-supply voltages. YOu found a suspect supply, I see. There's some really cheap little DC digital voltmeter boards from China for a few dollars. Putting a bunch of those on your DC lines may allow you to monitor them as you do repairs, look for sagging DC. Your "real" voltmeter can confirm the voltage; these widgets aren't that accurate but don't have to be. YOu might also 'scope out the DC, look for noise and glitches. As you know you need a lot of bandwidth to see DC spikes and dips which can trigger logic incorrectly. Also, chemical changes occur in board contacts as current flows. Corrosion over decades may create a bit of chemistry. Then when current is applied, chemistry (corrosion) may increase resistance between boards and their edge-sockets. Removal/insertion will fix that, for awhile. I've had good results with DeOxIt chemicals - even with those IC's with "black leads". A swipe of the DeOxIt brush across the board edge may work. I often follow that with some scrubbing with a white papertowel, to remove the oxide while maintaining that chemical coating. You can see dark-stuff come off. If there are pin contacts, a soft used toothbrush is a good scrubber. YOu don't want to "scrape", that removes gold and nickel! But you know these things. Point being: never underestimate the problems with "contacts". Herb Johnson -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net