I've been looking for schematics for this machine since the early 1990's, and as yet have come up dry. They just don't seem to be out there. My understanding is that generally, service technicians in the field were trained to repair the machines on a module basis, e.g., replace this circuit board if it exhibits this symptom. Service technicians didn't need schematics, because all they really needed was troubleshooting guide, a knowledge of general operating theory, good test equipment, and a kit full of every spare assembly needed. This made it unnecessary for them to repair things down to the component level, except in the case of the power supply, which may require replacement of individual components. Everything else was modular. As a result, field techs likely didn't need schematics -- and that was a good thing, because field techs could be 'loose' in their care of schematics, allowing copies to be made, leaving them behind, etc., which will generally not maliciously intended, could result in competitors getting their hands on the design, which, in those days as it is today, can be a big problem. The closest thing out there are the US Patents that describe the machine. The patents are quite detailed, and diagram everything at a 'building block' level. They are likely not a 100% accurate reflection of the actual productionn EC-130 (for a number of reasons), but they give a great level of detail about the architecture and methods by which the machine operates, and lots of logic-gate level "schematics", and timing diagrams. The relevant patent numbers are: 3465301, 3523282 and 3546676. You can get to these patents online through the US Patent & Trademark Office Website (www.uspto.gov). Nicholas Bodley (a former Friden service technician) wrote an essay on his memories of the architecture and operation of the machine. You can find this on my website at http://oldcalculatormuseum.com/nbodley. Reading this, combined with absorbing the data in the patents, can give someone with a solid electronics background a good idea of what is going on inside the machine. Making an extender board, and with good test instrumentation (a good four-channel oscilloscope is invaluable, and if one is available, a logic analyser with settable logic thresholds), it should be possible to track down where the problem lies. The most common problems with these machines are failures in the switched capacitor voltage multiplier that generates the 3KV for the CRT, problems with the delay line adjustments or component failuers in the delay line transmit and/or receive amplifiers, and lastly problems in the CRT deflection/drive circuitry. Failures in the logic package are pretty rare, actually. If you can describle the problem(s) you are seeing with the machine, I might be able to provide some hints. Rick Bensene The Old Calculator Web Museum http://oldcalculatormuseum.com Beavercreek, Oregon

You're generous... I would expect to be _given_ (as in, to keep afterwards) the machine if I was going to spend a few weeks/months producing schematics Amd that is a realistic estimate of the time IMHO. Reverse engineering is a lot easier if you have one or more large chips (processor, etc) that can eseentially only be used in one way. If you find, say, a 8250, it's a very good bet it's going to be part of a serial port, that there'll be an 8 bit data bus going into it, etc. If you just have a mass of 74xx gates and flip-flops, it could be almost anything. And a board of discretes is even worse, it might not even be digital. -tony

OK, ask me to reverse-engineer a complex machine without giving it to me and see how far you get... Yes, I do enjoy figuring out how things work, but the real reason I produce such diagrams is to keep my own machines running. Of course I share them with othes, but I am not going to spend a lot of time figuring out how to keep _your_ machine running unless I get something in return. That something is normally an example of the machine in question. I do make exceptions occasionally. If the machine is sufficiently simple that I can figure it out completely in a couple of days, then I might do it anyway (I do not own all the HP handhelds covered by the HPCC schematics CD-ROM, I borroowed many of them from other members). But I could produce a schematic for one of those in an afternoon at most. I do own all the desktops covered by that disk, producing diagrams for one of those takes weeks. -tony