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576 Printact relays contact wear


Ed Breya
 

Continuing on this 576, I removed the four Printact relay armature assemblies, and found that the gold plated contact pads on the board were quite pitted on the two uppermost units. I did not expect to see this kind of wear. I cleaned them all up with IPA and treated with Deoxit D100 then Deoxit Gold.

It seems to mostly work now. The original problem was that there where sort of random offset jumps between the 1-2-5 vertical gain steps - sometimes (usually) there would be an offset, and sometimes not, while rolling through the ranges. I adjusted the offset pots close enough now that it's quite good after warmup, but I still see an occasional jump, where a contact isn't working. While working on it, I kept the armatures organized so each would go back to its original spot. I'm thinking now it might be better to mix them up, so the worn spots on the board and armature contacts won't align, and instead make contact at "fresh" areas.

Ed