Heath H-1 analog computer

Dave McGuire wrote: Hi Dave, Great acquisition, and I saw where you are planning on changing or reforming the electrolytic caps. I would strongly recommend that you replace (or test with the appropriate tool - I'd use my Heathkit Capacitor tester) any and all of the other non-electrolytic caps. None of these were designed to last 50 some years, and are likely to be leaking due to age, this will lead to overheated resistors and possibly tube failures. Once the caps are tested then check the plate and cathode resistors to make sure they haven't drifted. You can normally check these in-circuit with modern multimeters. I would NOT try powering up this machine until the caps are tested/replaced, plus any 115VAC power cords are checked for brittle insulation. Many flexible wire cables from that period are now dried out and the insulation is brittle. Internal power wires also should be checked. Oh, and make sure the fuses are the correct ratings - sometimes people substitute something 'temporarily' - I've seen aluminum foil, wire, fuse holder shorted out completely, or vastly higher fuses installed... If the rectifiers are Selenium (look like fins on a stick) then sniff for signs or problems (rotten eggs is bad). If good, then carry on. If bad you can replace them with Silicon bridges, but you MUST check that the AC inputs to the bridge are fused, not the outputs as was common with Selenium. The reason Selenium were fused on the output was if the Selenium bridge virtually always fail open, whereas Silicon rectifiers short out - not good for the power transformer if unfused on the AC leads to the Silicon bridge.... John :-#)# -- John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames) www.flippers.com "Old pinballers never die, they just flip out"