How many people where, who restore and run old hardware, have never been caught out by a 'silly fault'? My guess (if you are honest) is exactly zero :-). I will admit to spending quite a time figuring out why all the outputs of a PSU were sitting at zero volts ony to discover the fuse in the mains plug was misisng (not blown, actaully removed). Or the time I spend a morning tracing waveforms through the video board ina VT101 to sort out a low-contrast problem, only to find the real fault was that the CRT screen needed a good clean. A piece of cardboard was a lot cheaper than trying to get a part out of DEC :-) -tony

What was the calculator? Some claim that calculators are off-topic here. I am not so sure. I can't think of any reasonable definition of (automatic digital) computer that would exclude user-programmable calculators [1]. And the non-programamble ones, while not strictly computers, are clearly related devices. [1] Also some manufacturers (HP being one) called machines 'calculators' for marketing reasons, mostly to get past purchasing departments who 'knew' that a computer was a machine from IBM that lived in an air conditioned room and needed a maintenance contract. I defy anyone to come up with a sensible defintion of personal computer that excludes the hP9830 (aka Model 30 calculator). Argh!. I've saind many times 'check the PSU first', but it's easy to forget, or to assume it's OK when the fault is actually a poor connection somewhere. I've had examples of both... In my PDP11/45, I had a curious fault that it would have all sorts of odd problems (memory erors, Unibus grants mising, tc) after running for aobut half an hour. I spent a long time going through the logic before I botheresd to check the 5V lines _at the backplane_. One was sitting at about 4.4V. ... And my PERQ3a had strange hard disk problems. It turend out there's an in-line fuseholder (like the ones used in some older cars) in the 12V feed to the winchester disk. The wires were held in by little grubscrews and one was loose. Tightneing it cured the problem. You mean you didn't put the origiunal IC back in? When I was restoring my HP9820, I found the main reason that the processor wasn't working was that there were problems with the M (memory address) register. This is a 6 bit bit-serial machine, and bits are shifted into the registers from the most significant end. Anyway, bits 15..12 of the M register were changing, the rest were stuck at 0. The register is made of 4 4-bit TTL shift registers (7495 IIRC), and after managing to obtain some, I changed the one for bits 11..8. This had no effect on the fualt. Not only did the processor still not work, but also the M register behaviour was unchanged. I looked more carefully at the bits that were changing and realised the timing was all wrong. The seiral input to the 11..8 chip was always low on the active edge of the clock. So I replaced the top bits register using the one I'd desoldered Yes I did reulse that old bnut good chip. 7495s are too rare to waste! -tony

Hi According to some sources, this type of thinking is what killed the Canon Cat. One line of thinking was that the Canon computer division learned that it was a computer and not just a fancy electronic typewriter. There is another line that it was related to Canons work with the Next project. It was stated that the Cats didn't sell but in fact they were back ordered. There was also a more notebook like one in the design stages when shut down. One often wonders how the netbook and similar devices might have evolved had the Cat had more influence. Dwight _________________________________________________________________ Hotmail has tools for the New Busy. Search, chat and e-mail from your inbox. http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:…