Dave Caroline wrote: Will see what I can do! Thankfully the card-cage hinges, so I should be able to take a photo without any serious dismantling! I made a note of the text on the capacitors earlier: CIRCE MCB1000 uF1000V12 and CIRCE MCC1000 uF1000V25 ... which at least gives manufacturer and apparent part number (MCC/MCB 1000) along with the spec. The end caps are just blobs of coloured resin/plastic around the axial leads, rather than being some form of made-for-the-purpose thing. No doubt common in equipment of this era... I wonder if there's any reason to disconnect the Nixie display too whilst initially powering the cards? (i.e. are Nixies particularly prone to any sudden changes in voltage, such as might be brought about if something on one of the cards decides to let go?) cheers Jules

On 5/14/07, Jules Richardson <julesrichardsonuk at yahoo.co.uk> wrote: green cap end is past of major on a Not sure on the capacitors. My IME-86 doesn't have any capacitors like this -- all of the ones in mine are actually marked + and -. If you've replaced the capacitors, there's really no need to use the variac to power it up. Typically, the variac is used to slowly ramp the power up to allow old capacitors to be observed to make sure none start leaking or smoking. Other times variacs are used (typically with a dummy load in place of the actual calculator circuitry) to perform capacitor reformation. One thing that using a variac to power up a machine like this is that power--on initialization circuitry can become quite confused when the power doesn't come up at the normal rate. This can mean that when the variac gets up to full voltage, the calculator may "act" dead, and require pressing "CLEAR" to reset the machine. Sometimes, though, this doesn't even work as the logic is so locked up that the "CLEAR" key won't even make it right. The suggestion of powering up with a smaller fuse in place is a good idea, though you have to be careful, as if the fuse pops, you're not really sure if it popped because the rating is too low, or if there's a fault which caused it to blow. One thing that I'd recommend before powering it up is to pull all of the cards (except the core card, which is hard-wired in IIRC), and clean all of the edge connector fingers. Even light levels of corrosion on the edge connector fingers can cause enough resistance to throw off the logic levels and cause the machine to malfunction. IME's early calculators are quite wonderful machines. The machines have a particularly interesting legacy in that the Japanese company Nippon Computing Machine (a.k.a. Busicom) copied the early IME designs to create their first calculator. NCM/Busicom became famous for developing the first electronic calculator (in conjunction with Intel) to utilize a microprocessor (the Intel 8008) rather than a hard-wired or microprogrammed calculator-specific architecture. Rick Bensene The Old Calculator Web Museum http://oldcalculatormuseum.com

Anytime you use a variac, it is wise to put a current limiter in series. This can be done easily with an incandescent bulb (about 60W or 75W). This prevents any surge entering the circuit if there is a short. The surge in power cause the lamp to glow very bright which creates high resistance thus reducing the current. When a unit is functioning properly without any shorts at nominal voltage, the bulb will just have a faint dim.This is the oldest trick in the book. =Dan [ My Corner of Cyberspace http://ragooman.home.comcast.net/ ] Chuck Guzis wrote:

Apparently, you may not realize that a variac can burn up too--variacs cost a pretty penny. The current limiter is a preventive measure. Switched mode power supply designs are used in many applications, beginning with of all places, a modern computer monitor. Variacs have proven to be a valuable tool to diagnose a lot of symptoms.You may want to research this small bit of troubleshooting methodology even further. I wouldn't like to think all our repair manuals have been erroneously filled with uneducated gibberish. :) =Dan

On 14 May 2007 at 21:53, dwight elvey wrote: Tantalums going don't scare me--and neither do old electrolytics blowing their seals. What really scares me are those old steel- jacketed-epoxy-sealed caps that you can often find in old military gear. I've had one or two of those blow suddenly and leave shrapnel in the ceiling. Loud and scary. Cheers, Chuck

Rick Bensene wrote: You're lucky :-) I suspect it's the same power board, just with different parts (Looking from the back: four vertical 1000uF at 12V capacitors on the left, three vertical 1000uF at 25V capacitors on the right, then below these are two 100uF at 100V horizontal capacitors on the left and one 1000uF at 25V horizontal capacitor on the right) The two 100V ones are copper-coloured and are marked with +/-, it's just the others that are silver and have the coloured end caps. Noted - thanks. I was mainly wondering about the caps on the cards, but then I suppose these are all fed from supply rails that are no doubt regulated, so there's no way to bring them up slowly. Will do. I've had all the cards in the right-hand cage out already and everything *looks* remarkably clean, but then appearances can be deceptive :-) I'm yet to look at the left-hand cage (which contains the core) - I think I could see a few electrolytics in there which will need inspecting. I'm a sucker for anything with Nixies inside :-) Plus I've wanted an early electronic calculator for quite some time, so it was too good to ignore. It cleaned up really well (there was a *lot* of dirt on the outside, despite the inside being so clean). The keyboard panel's slightly less than perfect though, with a couple of scratches - I can't decide whether to strip and respray it in as close to original colour as possible, or whether to keep it as-is, warts and all. I'm saving that call for after I see how close to working it is! cheers Jules

Warren Wolfe wrote: I had that sort of thing at the back of my mind - but a variac often seems to come up when systems which have linear PSUs are mentioned. Like you say, it seems highly dependent on the circuit in question... That does perhaps seem a better approach, given the unknowns. I'll run the supply up first with no cards in place. I'm not sure whether it's wise to give it a dummy load or not... I suppose it is, purely from the point of view that it might encourage anything in the PSU circuit that's going to let go to do so when there aren't "expensive" boards in place. (That in turn begs the question: does anyone with one of these calculators happen to have the PSU test points / correct output voltages noted down already?) cheers J.