test-drb July 1997

test-drb@ccmp.vtda.org

111 participants
442 discussions

FAQ addition: Repairing Capacitive Keyboards

by ard＠p850ug1.demon.co.uk

In message <51194C00BD39CF11839000805F385DB20578947C(a)RED-65-MSG.dns.microsoft.com> classiccmp(a)u.washington.edu writes: > REPAIRING CAPACITIVE KEYBOARDS > v1.0 7/10/97 Kai Kaltenbach > > ---> What are capacitive keyboards? > > The vast majority of capacitive keyboards were and are manufactured by > Keytronics of Spokane, Washington. The mechanism is really quite > simple. A keypress pushes a foil circle onto the surface of a printed Note that the foil (actually a metal layer) is on the inside surface of a plastic disk on the end of the key plunger. It doesn't actually make contact with the PCB > circuit board, thus completing the circuit and registering the keypress More correctly it increases the capacitance between 2 tracks on the PCB. > to the computer. Capacitive keyboards are very reliable; however, they > will fail over time even if unused. > > Each foil contact circle is backed by a cylinder of PVC foam. The foam > is subject to environmental deterioration. Once the foam loses its > elasticity or dissolves entirely, the keys will stop working because the > foil circles will no longer make good contact with the PC board. > Various classic computer systems, such as the Processor Technology Sol, > exhibit this problem after their 20+ year lifespan. I've once seen a fault where the metal layer vanished, leaving the foam intact. No idea what happened, but it didn't work, of course. > > ---> How do I tell if I have a capacitive keyboard? > > Just remove a key cap -- if there is a separate spring under the key > cap, around the plunger, it's extremely likely that it's a capacitive > keyboard. They won't always say Keytronic on the outside of the > keyboard housing. These keyboards are _everywhere_. I've seen them 'made' by PERQ, Apricot, Acorn, Tektronix, FTS, and probably more. The only problem is that some of those are classics in themselves, and probably shouldn't be raided for spares. > > ---> What do I need to start a repair job? > > First you need a set of replacement foam pads. Each foam pad is a > cylinder about 1/4" in diameter and 3/16" long. There is a semi-rigid > clear plastic circle attached to one end of the pad, and a foil cylinder > attached to the other end. > > The only toosl you'll need are a #1 Philips screwdriver and a very small > standard screwdriver such as those pen-clip types frequently included in Every Keytronics keyboard I've dismantled has needed a smaller Phillips screwdriver (size O?) to remove the PCB from the keyframe. > computer tool kits (plus whatever tools are necessary to remove the > keyboard from its enclosure). > > ---> Where do I get replacement pads? > > If you're a perfectionist, you can order replacement pads from Keytronic > Corporation (http://www.keytronic.com/). However, it's much easier to Seriously? Do they do other spares as well. There's a couple of custom chips (see below) in almost all of these keyboards, and a source of spares would be handy. > simply find a capacitive keyboard in your local computer junk/surplus > store and strip it for replacement pads (see above for info on > identifying such keyboards). -----> So, What are the Custom Chips ? There are, in general 2 off 20 pin custom chips in a keytronics keyboard (some later ones have a single 40 pin chip, but I know nothing about that). 22-908-3B 8-channel sense amplifier 1 : Row 0 2 : Row 1 3 : Row 2 4 : Row 3 5 : Reset/sync output 6 : Row 4 7 : Row 5 8 : Row 6 9 : Row 7 10 : Ground 11 : Out 7 12 : Out 6 13 : Out 5 14 : Out 4 15 : Out 3 16 : Out 2 17 : Out 1 18 : Out 0 19 : Reset in 20 : +5V Outputs are believed to be open-collector 22-950-3B keyboard column decoder/driver. 1 : Col 8 2 : Col 9 3 : Col 10 4 : Col 11 5 : Latch Clock 6 : Select 0 (LSB Input) 7 : Select 1 8 : Select 2 9 : Select 3 10 : Ground 11 : Sync Input 12 : Col 0 13 : Col 1 14 : Col 2 15 : Col 3 16 : Col 4 17 : Col 5 18 : Col 6 19 : Col 7 20 : +5V -tony

27 years, 11 months

What Classic Computer are All About - A Lovers View

by ard＠p850ug1.demon.co.uk

In message <Pine.SOL.3.95.970710232706.10063D-100000@typhoon> classiccmp(a)u.washington.edu writes: > > of the old machines. I collect, but I admit is has to make some sense to > > me as in useful or have some specific linkage to my place in this > > history. > > But this is a collectors list 8-) We all collect from that which we know. Not necessarily. I've bought things at radio rallies (hamfests) because 'it looked interesting'. Only later did I discover what I really had. If I'd always waited to find out what a particular item really was, then I'd probably have missed all the interesting stuff, and have a totally trivial collection. However, it does help to have some idea as to what things are. And to know what they look like from all angles :-) > You must have been - what - 8 years old 8-) Great story! I think we all > have one of those - where everybody kinda stares at you - wondering - > What the Hell is THAT? What are you doing with that - THING? Yep, got a load of them. Taking a trolley piled high with computer parts across Cambridge on a weekday afternoon is good for that :-). Or the time I carried a DEC Rainbow on a train - VR201 in one hand (using the built-in handle), CPU under the other arm, and keyboard in my pocket. Dismantling the CPU mid-journey (it needs no tools) added to the amusement. Then there was the time I carried an IBM PC/AT box on a train. It got the comment 'That's one hell of a laptop' :-). Or the time I was carrying a Creed 7E (baudot printing terminal) and was asked if I had a pen. My reply was 'no, but I have a teleprinter' :-) Still, what's wrong with being slightly mad? > > BC > > -tony

27 years, 11 months

What Classic Computer are All About - A Lovers View

by ard＠p850ug1.demon.co.uk

In message <Pine.SOL.3.95.970710191732.26431A-100000@typhoon> classiccmp(a)u.washington.edu writes: > > First - if you don't want to hear my opinion - stop now! I am going to > get pretty detailed about what the list is/should be about. I may hurt > some feelings - but well hell - that's life! Is it time to start a classic computers meta-list to discuss what should be on the classic computers list ? > Currently, this list is set on the aquistion of hardware. One reason > is to get it before it's GONE. Another, is the ECONOMY of collecting. > (I buy it for 10 and sell it for 15 Sam 8-) The point being, in two > years, if we did nothing - you may NEVER be able to buy it because > someone junked it! Nothing wrong with making hay while the sun shines. Absolutely. In some cases, the number of remaining machines of a particular type can be counted on the fingers of one hand - in unary :-). If we don't grab them when we can, then information on these machines will be lost for ever. > > The history of computing doesn't lend itself to the IMMEDIACY of hardware. > The history of computing IS. There is no cost in learning it, > understanding it, and aquiring it. I think I disagree here. It's a lot easier to figure out the history of a machine while the people who used it for real work (and even better the people who designed/built it) are still alive, and can still remember the machine. So there's some urgency here, but less than the 'Here's a 1-off prototype that will go in the skip if you don't get it today' type of thing. A lot of computer history, particularly over the last 20 or so years has not (IMHO) been adequately recorded. What I'd love to see would be complete documentation on all the classic computers - how the hardware worked, how the software worked, when it was introduced, why it was introduced, what went wrong, what should have been done differently, what was good about it, etc. But to do that for just _one_ machine would be a major undertaking (I've tried writing some hardware docs, and it takes a long time!). But some of that info is likely to die with the _designers_, not with the machines, alas. > I would probably die if someone wanted to give me the Intellec MDS that > Gary wrote CPM on. That is too much to hope for in this world 8-) Aside : It's probably possible to find a similar machine (although not _THE_ one) if you hunt for long enough. I've found an CS8i and an MDS800 second-hand. > I also get a little perturbed when people state "This Weekends Haul". The main reason I get little from these messages is that the situation is very different in different countries (Acorn machines are lot easier to find in the UK than in the States, while CoCo3's are almost unknown over here). And of coure prices are very different as well. > BC -tony

27 years, 11 months

Modem Collection

by ard＠p850ug1.demon.co.uk

In message <33C673A3.6EA5(a)rain.org> classiccmp(a)u.washington.edu writes: > Just curious (again!) if anyone is collecting the early modems used on > computers and what might have been the earliest commercial phone modem. I've got a few (I'm interested in telegraph and telephone history as well as computers, but my main collection is computer-related). It's not a large part of my collection, though. In the UK, modems were _rented_ from the GPO (== post office, who also ran the telephone system) at one time, like all other telephone equipment. Some of these modems are interesting technically - the earlier ones were about 14" square and 6" high, and contained plug-in modules for the PSU, modulator, demodulator, and controller. It was all discrete components (no chips), and some of the control used PO 3000-style relays (similar to the ones used in telephone exchanges). The demodulator was strange. It filtered the incoming signal (a multi-stage LC filter housed in a tobacco-tin sized box!), and then mixed it with a local oscillator to shift the frequency up. The output of that was filtered again, and fed to a 2-diode discriminator. The output of that was buffered and became the data output. It was basically a superhet FM receiver modified to work at the right frequency. Another strange GPO modem was the 13A. It's a 1" (approx) high plinth that was fitted under a Type 746 'phone that had extra 'voice' and 'data' buttons fitted. I know nothing about the circuitry in that one, but it's a rather neat unit. There were also things called 'isolation boxes' that were used to prevent faults in the user's equipment damaging the modem (or worse still the 'phone line). Typically they contained a number of zener diodes from each line of the RS232 connector to ground (2 diodes in inverse series per line), and some 50mA fuses in series with each line that would blow if there was overvoltage on that line. Such things are probably useless now, but I like to have all the bits of a classic setup, including little details such as this. > I have several devices that are called modem eliminators and I believe The term 'modem eliminator' normally meant 'null modem cable', and was a passive device. -tony

27 years, 11 months

History of Video Games (RE: "Bally Astrocade")

by kaikal＠MICROSOFT.com

Yep, that was Cinematronic's excellent vector version of Space War, released in 1978. It was two-player only, and had several innovations, including the ability to shoot off part of your opponent's ship, and the selection of multiple game options at the start of your game (e.g. positive/negative gravity, invisible sun, etc.) The upright cabinet was huge, almost double-wide, but I would dearly love to come up with the cocktail version (http://brain.usask.ca/arcade/spacewar.htm) It'd be a nice complement to my Computer Space. Kai > ---------- > From: Ward Griffiths and/or Lisa Rogers > Reply To: classiccmp(a)u.washington.edu > Sent: Friday, July 11, 1997 11:05 AM > To: Discussion re-collecting of classic computers > Subject: Re: History of Video Games (RE: "Bally Astrocade") > > On Fri, 11 Jul 1997, Kai Kaltenbach wrote: > > > Studio II, which were introduced simultaneously in 1976. The first > > vector graphic arcade game was Lunar Lander in 1979, followed by > > Asteroids later that year. The first (and only) vector graphic home > > I seem to recall spending many many hours (and quarters) with my > roommate > playing a vector graphic arcade version of Space War when we were > fresh > out of the USAF back in 1978 and spending loose hours at the Saint > James > Infirmary in Sunnyvale. > -- > Ward Griffiths > "America is at that awkward stage. It's too late to work within > the system, but too early to shoot the bastards." --Claire Wolfe >

27 years, 11 months

Modem Collection

by fmc＠reanimators.org

Marvin <marvin(a)rain.org> writes: > Just curious (again!) if anyone is collecting the early modems used on > computers and what might have been the earliest commercial phone modem. I have a few, but not what I would call "early". An old Omnitec 701A (s/n 3) acoustic coupler that I used to use with a Teletype ca. 1978 (still worked when I tried it about a year ago, too). Also some S-100 modems, including a couple each of PMMI MM-103 and Hayes Micromodem 100, and what I am guessing is an earlier (1978) effort by D. C. Hayes called the 80-103A. > I have several devices that are called modem eliminators and I believe > these are basically serial cable boosters to increase the permissible > cable length. It depends. They may also provide clock signals for synchronous DTEs (as would ordinarily be done by the modems). -Frank McConnell

27 years, 11 months

Old Microprocessors

by bluesky6＠ix.netcom.com

Some days ago, I mentioned that there was a UK company that used to advertise old microprocessors like 9900, Z800x, 32032 and other stuff. I've just dug up my old issues of Elektor and found the company. It's Viewcom, at Plaistow in London. Perhaps Enrico might want to check if this company still exists and its tel/fax number: I've been looking for a 10MHz Z8001 (the one found in Ciarcia's Trump card project in Byte). The April 1991 issue of Elektor advertises Viewcom as carrying stuff like the 9900, 9995 (both TI 16-bit microP). There's even the AMD 9511 which (if I'm not mistaken) is one of the first math copros for microcomputers. Interestingly, there's another ad. for a little machine called the midi65, which uses a 6501 (the number was re-used by Rockwell for a dual-65C02-on-a-chip implementation) with LCD display. Of course, then there are the usual surplus ads from Display Electronics (VAX11/750 for 3900 pounds sterling and the Tatung PC2000 a big brother of the CP/M Einstein for 299 pounds sterling) and J&N BULL Electrical (which offers an Atari 65XE computer for 45 pounds sterling). Ben

27 years, 11 months

IBM minis still humming

by william＠ans.net

Yesterday, I finally received the chance to examine a family of computers that has been bugging me for a while. In the mid to late 1970s, IBM introduced a family of minis designed to kill the PDP-11, or so they thought. The series/1 is a bit different, in that they are not designed to run COBOL applications in a business environment. They are also very modular, something that other IBM offerings are not. I saw about 25 of the big beasts, all humming away at thier duties, and of course, now want one (love at first sight, it happens alot with collectors). Unfortunately, I am still lacking just about all technical information about the family. Has anyone on the list ever use one of these things? What operating system did it use? Just how good (or bad, probably) are these things? Oh, sorry about repeating the modem information! William Donzelli william(a)ans.net

27 years, 11 months

Paper Tape

by 107765.1161＠compuserve.com

As most of you probably know, some of the old printing terminal (teletype) units could utilize paper tape; the tape could be punched with a program, and hence used as a program storage media. I'd be interested in getting a bit of the tape; not real long (say, 4-6 feet), just for show-and-tell purposes. "Already punched" would be better than "unpunched" ("unpunched" might just look like a roll of adding machine paper-- big deal), but I'd take either. If somebody has some of this to spare, please drop me a note e-mail; I'd appreciate it. Gil Parrish 107765.1161(a)compuserve.com

27 years, 11 months

Modem Collection

by allisonp＠world.std.com

> From: Marvin <marvin(a)rain.org> > Just curious (again!) if anyone is collecting the early modems used on > computers and what might have been the earliest commercial phone modem. > I have several devices that are called modem eliminators and I believe > these are basically serial cable boosters to increase the permissible > cable length. My guess is that the earliest modems were accousticle > (sp?) modems where the coupling was where the phone was laid onto the > modem rather than a direct connect to the computer. Was there anythin > earlier or other type of device? Early modems were mostly acoustical as it was a way of avoiding the BELL TELEPHONE CO tarriff and interconnection restrictions. There were also direct connect bell103 is well known of them. They go way back, to the old rtty machines used during WWII maybe before. Yes, those would have vacuum tubes. The modem eliminators were rs232 or current loop to rs422 which could be used up to several thousand feet or more. These were not modems per se but level translators to a format that worked well on hard copper pairs at what would be then called high speeds (4800 ->38.4++). Allison

27 years, 11 months

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test-drb July 1997