Vintage computer finds at the Sussex Hamfest
I was at Sussex as a buyer, got there about 9:30AM. Of course I saw Jeff Galinat, he showed me the KIM he obtained. It was a good show as is usually the case, Sussex is one of the largest hamfests in NJ now. But there was not much vintage computing there, or it was sold earlier in the day if brought. I left around noon, when most but not all the vendors left: by then it was hot, clear and muggy - probably upper 90's heat index. I saw a 8086 in-circuit emulator, but I do very little with the 8086, more with the 8088, so I let it pass. A few books were on 70's computing or on robotics, I bought those. Parts were of all kinds, I got some discounted IC sockets and on a lark, 200 removed NE2 neon lamps. A Radio Shack bulk-tape eraser was cheap - the grey device that looks like a hand-mixer without the twirley-bits. Handfuls of parts, otherwise. I see a number of 20Mhz-40Mhz oscilloscopes at the hamfests, which go begging. Most are secondary brand, some are not; most work. Seems to me, for not much more spent than for a logic probe, one can get a much MUCH more informative test instrument. I acquired two, which worked back home but need some mechanical repairs. I may make these available at a convenient venue. I saw several people in our vintage-computing world who recognized me, or I them. It's a good opportunity to see people who live north of New Jersey. It's pretty low-mountain country up there, and there's good mid-20th-C. diner food. The geology in Sussex County is interesting and in some cases world-class (the Sterling fluorite mine, colonial iron-mines). Herb Johnson -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net
I see a number of 20Mhz-40Mhz oscilloscopes at the hamfests, which go begging. Most are secondary brand, some are not; most work. Seems to me, for not much more spent than for a logic probe, one can get a much MUCH more informative test instrument.
Agreed, I've made several available on the Vintage Computer Forums for what I thought was a reasonable price, but no one was interested. One of those tools you're going to absolutely need one day, when the logic probe won't cut it. Fortunately for vintage computer work, it doesn't need to be fast, but you'll find all sorts of people on the forums telling others they need at least a 100 MHz 'scope with four channels and digital storage. Perhaps that's why people aren't interested in 20 MHz "student" or "TV" 'scopes but will spend money on USB connected devices that claim 100+ MHz bandwidth... Thanks, Jonathan
Jonathan wrote:
Perhaps that's why people aren't interested in 20 MHz "student" or "TV" 'scopes but will spend money on USB connected device that claim 100+ MHz bandwidth...
Jonathan knows about, what I'm about to post.... Note that I cast those 20-40Mhz scopes as alternatives to logic probes; a low bar. It defies my old-person 20th century mind, that someone would try to debug TTL logic and 4MHz processors with a logic probe and interpret a blinking LED. When most any 'scope with triggered sweep will provide means to check timing and logic states at 8-bit processor speeds. Not to mention, funny logic levels that will confuse gates, and indicate fried TTL drivers or possibly shorted lines and connections. I'd say most 1970's microcomputer failures could be "caught" with this class of oscilloscopes, used with some knowledge and experience and a TTL data book. What such scopes won't do, is catch "glitches", odd logic events due to faulty timing or noise artifacts treated as logic signals. That's when a 100Mhz true analog bandwidth starts to become useful. And at that, you may need a storage 'scope to catch one-off events. While I've bought and used simple "TV repairperson scopes" - I actually see better 'scopes than that, go begging. One I picked up Sunday, has some kind of digital storage, but otherwise analog. The other is a lower-end Tek scope with some digital controls. One acquired late last year, was 40Mhz and had some digital display features. As for USB-based "oscilloscopes", those are analog-digitizing devices which use a PC for display and operation. Sample rate does not equal bandwidth, an LCD does not equal a CRT. (hooking thumbs in suspenders) While I don't know much about 'dem fancy, hew-hess-bee, citi-fied ways of readin' logic levels; it seems to me that an honest, middlin' bandwidth, analog 'scope, with a bright green CRT, can do the job, 'jest *fine*. I'll take a bank of ten-turn potentiometers and toggles, over a click-and-pray virtual test panel, any day. Uncle Herb -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net preservation of 1970's computing email: hjohnson AAT retrotechnology DOTT com alternate: herbjohnson ATT retrotechnology DOTT info
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