- vcf-midatlantic - lists.vcfed.org

Simpson 262 Series E
by Paul Birkel 16 Nov '15

16 Nov '15

As long as we're talking about Simpson 260 multimeters ... I have a Simpson 262 Series E that suffered battery-failure (x2) in its former life. I'd like to put it back into service (for the reasons that Dave states, below), and aside from fixing the corrosion at the battery contacts (pointers anyone?) I've been "put off" by the problem of finding affordable modern substitutes for the pair of 15v batteries used in the higher resistance ranges. Any suggestions for a suitable substitute for the 30v (total) battery requirement? -----Original Message----- From: vcf-midatlantic [mailto:vcf-midatlantic-bounces@lists.vintagecomputerfederation.org] On Behalf Of David Riley via vcf-midatlantic Sent: Monday, November 16, 2015 10:46 AM To: vcf-midatlantic Cc: David Riley Subject: Re: [vcf-midatlantic] Apple IIe Voltmeter On Nov 13, 2015, at 11:59 AM, Herb Johnson via vcf-midatlantic <vcf-midatlantic(a)lists.vintagecomputerfederation.org> wrote: > > I prefer analog meters when making "runs" of comparative measurements. It's easy to see if one reading is "more" or "less" than another, the needle is literally in different positions. I prefer them for that and, for diagnosing intermediate or "wandering" problems (or quickly checking continuity), it's MUCH easier to see a needle moving than wait for the update of an LCD. > I've found variations in current measurements among several Simpson 260 meters (and among their scales) I've acquired. My guess is that some of the shunts were "cooked" by excessive current, or corroded by time and tide. I have not yet gone to the trouble of diagnosing them, I simply use the meters that have the best readings through the procedures noted. They are cheap today. I've definitely cooked current shunts in both digital and analog meters. Nothing is immune, even the fused ones (those fuses do have a finite blow time, which is more than enough to damage something if you accidentally touch mains). > Why? Given the "digital is better" bias these days, only a few people call out the Simpson 260 as a valued instrument - Dave McGuire for instance, in that email list we used to use. Digital is marginally better in situations where you need to record a number, but that's really just laziness. They can actually be more precise where that matters, but it seldom does. And I like the autoranging of digital meters, but that goes back to laziness. I have a very nice Fluke 87-V that I use for just about everything, but there are a lot of times I wish I had a dependable and portable analog meter as a counterpart. - Dave

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Current Loop Converter Update -- Modularizing
by Systems Glitch 16 Nov '15

16 Nov '15

Continuing the saga of designing a "tries to meet all requirements" current loop converter, I've decided to redo it as a modular design with separate modules for: - Loop supply - Receive converter - Transmit converter This will make the board smaller, plus you won't have to populate the modules you don't need. They'll also be available for inclusion in other projects. The edge connector spacing is intended to mate with Digi-Klips or have 0.1" pin headers soldered on. It's a single-inline connector, so it's breadboard friendly too. Here's some pictures of the 24V isolated loop supply module: http://imgur.com/a/U9RMK I'll probably end up using that module in projects not related to the current loop project, too! Thanks, Jonathan

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Re: [vcf-midatlantic] Festivus food thread: Who's bringing what?
by VAXman＠tmesis.org 16 Nov '15

16 Nov '15

Evan Koblentz via vcf-midatlantic writes: >>> I'll be bringing some homebrew; I have a winter warmer that's come >out = >> pretty well that I can bring at least 12 of (maybe a case). >Probably = >> not enough to stave off Brian bringing the good black >stuff. :-) Evan, > > I wasn't planning to lug the Guinness to Festivus. > I won't be staying the > evening which would not be a problem because >I've left the kit there in the > past and I retrieved it the next day. >However, there's a rocket launch on > that Sunday, so I won't be able to >pick up the kit on Sunday. > >No problem, there will be plenty to drink between Corey L.'s beer + >David's + whatever anyone else brings + Neil's apple cider. I may bring some beer, just not the whole keg/kegerator.

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[midatlanticretro] New York Historical Society : Silicon City: Computer History Made in New York
by Herb Johnson 16 Nov '15

16 Nov '15

> Christian Liendo wrote: > I went the previous Sat to see it only to find out it > was this past Sat. The museum Web page says it's an ongoing exhibit. What did you see on exhibit? The Web page shows only four photos. And by the way: those "New York" history photos represent Bell Labs (NJ) and Eniac (PA). So the exhibit likely represents work done in in the region. Wonder how far north they'll go? Herb -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net

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Re: [vcf-midatlantic] Festivus food thread: Who's bringing what?
by VAXman＠tmesis.org 16 Nov '15

16 Nov '15

David Riley via vcf-midatlantic writes: >On Nov 12, 2015, at 4:41 PM, Evan Koblentz via vcf-midatlantic = ><vcf-midatlantic(a)lists.vintagecomputerfederation.org> wrote: > >> Ps. OMARC is loaning us their grill. Someone should bring a full = >propane tank. > >I'll do that. I'll also be glad to bring pre-cooked pasta and a camp = >stove if someone else does the sauce; that worked well last year despite >= the spill. > >I'll be bringing some homebrew; I have a winter warmer that's come out = >pretty well that I can bring at least 12 of (maybe a case). Probably = >not enough to stave off Brian bringing the good black stuff. :-) Evan, I wasn't planning to lug the Guinness to Festivus. I won't be staying the evening which would not be a problem because I've left the kit there in the past and I retrieved it the next day. However, there's a rocket launch on that Sunday, so I won't be able to pick up the kit on Sunday.

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Apple IIe Voltmeter
by Herb Johnson 16 Nov '15

16 Nov '15

> [I had no way] to precisely measure current. My other bench meters are analog, > lowish impedance, and not precise enough to measure voltage drop > across a small-value resistor. Additionally, my Simpson 260 and > Simpson 160 meters don't agree on the 100 mA scales -- > I believe the Simpson 160 is correct, but needed a way to figure out. My experience is that digital voltmeters put too much current load on a circuit, when measuring DC current at tens of mA. Put another way: they have significant series resistance and change the circuit, and so change the current. Your A/D technology also puts a load on the circuit, you can read off the schematic or parts to determine that. But I found my Simpson 260 and other analog meters, put LESS load because they generally use 50uA movements (hence 20,000 ohms per volt, do the math). As to "figuring out the accuracy".....create a 10mA circuit from an accurately-measured battery and an accurately-measured resistor. Say 5V and 500 ohms, or whatever - the DVM can measure those fine, other resistors give other current sources, and math gives you the exact current. Many batteries can generally supply 10mA stable for minutes and hours or more, and your DVM can monitor their voltage anyway. Then make those circuits with the Simpsons and recalibrate the scales, and create conversion factors (or fitness for use choice) for each meter AND for each scale. YOu can use the same apparatus to calibrate your Apple II "meter". I prefer analog meters when making "runs" of comparative measurements. It's easy to see if one reading is "more" or "less" than another, the needle is literally in different positions. I've found variations in current measurements among several Simpson 260 meters (and among their scales) I've acquired. My guess is that some of the shunts were "cooked" by excessive current, or corroded by time and tide. I have not yet gone to the trouble of diagnosing them, I simply use the meters that have the best readings through the procedures noted. They are cheap today. Why? Given the "digital is better" bias these days, only a few people call out the Simpson 260 as a valued instrument - Dave McGuire for instance, in that email list we used to use. Jonathan, if you determine a cause for your analog meter's apparent errors, let me know. Herb Johnson old-school -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com

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Re: [vcf-midatlantic] [midatlanticretro] New York Historical Society : Silicon City: Computer History Made in New York
by Evan Koblentz 16 Nov '15

16 Nov '15

> https://www.nyhistory.org/exhibitions/silicon-city-computer-history-made-ne… > > They sent me an invitation to represent our group. Crap. I forgot to attend the ceremony last week.

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Re: [vcf-midatlantic] Festivus food thread: Who's bringing what?
by VAXman＠tmesis.org 16 Nov '15

16 Nov '15

Tony Bogan via vcf-midatlantic writes: >I thought the same thing! But I don't have a jolt cola or Mountain Dew >dispe= nser and also figured some might bring some family members during >the day :-= )= Start 'em young! ;) FWIW, when I did a computer security gig for M&M Mars many years back, one of the M&Ms remarked that he was surprised that my lunch didn't consist of Jolt cola and Twinkies. Yet another stupid Hollywood induced stereotyping of computer hackers.

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Re: [vcf-midatlantic] Festivus food thread: Who's bringing what?
by VAXman＠tmesis.org 16 Nov '15

16 Nov '15

Tony Bogan via vcf-midatlantic writes: >M > >Sent from my iPhone > >On Nov 15, 2015, at 9:36 PM, Evan Koblentz via vcf-midatlantic ><vcf-midatlan= tic(a)lists.vintagecomputerfederation.org> wrote: > >>>>> VCF will provide: burgers, beef hot dogs, rolls, common toppings, >commo= n >>>> snacks (chips, pretzels, etc), soft drinks, bottled water >>>>>=20 >>>> Guesstimated attendance is three dozen nerds... >>> Evan: >tray of soft pretzels >>> Corey L., via Kelly: beer >>> Vaxman: pork >ribs >>> Neil: Fudge Nut Brownies, Apple Cider Doughnuts > >> Tony: >Brownies, cookies, cupcakes, etc. > >> Chris F. Plastic utensils, >napkins >=20 >=20 > We still need volunteers to bring: > - paper or >plastic plates > - cold drink cups, styrofoam coffee cups > - coffee, >machine, cream, sugar, stir-ers, etc. > - any other appetizers / sides / >entrees beside red meat > - any other desserts / snacks > - Be creative: >anything else??? > >I can bring styrofoam plates, coffee, machines, (2 - 55 cup machines, >one fo= r regular and one for decaf) styrofoam cups for coffee too. Have >those in sp= ades for the boats. Coffee fixins' can be someone else's >domain :-) (especia= lly since I don't drink coffee!) Tony= Decaf? For computer geeks? :)

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Re: [vcf-midatlantic] Apple IIe Voltmeter
by tom.hornberger＠verizon.net 15 Nov '15

15 Nov '15

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