test-drb February 2000

test-drb@ccmp.vtda.org

162 participants
585 discussions

by apple＠cmc.net

Germanium diodes have the least amount of voltage drop while conducting (about .06 volts I think) and a popular one that should be readily available is the 1N34 or 1N34A. The reason that diodes seem to act funny on an ohmmeter is because of the fwd voltage drop while conducting. The silicon diodes that you probably got at radio shack have a fwd drop of more than .5 volts and will appear as a high resistance to your meter even though they are conducting. Hope this helps Noble -----Original Message----- From: Bill Sudbrink <bill(a)chipware.com> To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org> Date: Tuesday, February 22, 2000 1:44 PM Subject: Diode help... HELP! >Hi, > >Once again demonstrating my vast quantities of ignorance... >I need a diode which completely blocks current in one direction >and presents as little resistance in the other direction >as possible. I bought a fist full of little glass ones at >Radio Shack for 50 cents. On my Ohm meter, they show no >conductance in one direction and 1400KOhm the other way. >What do I need to get? RS (which is the only resource I >have available, I need them like _NOW_) has many different >kinds of diodes, ranging up to two dollars per pair. > >Thanks, >Bill Sudbrink

24 years, 4 months

Diode help... HELP!

by jeff.kaneko＠juno.com

Bill: You should test your diodes with an OHM Meter that has a high enough test voltage to overcome the barrier potential of approx 700mV for a silicon, and about 300mV for a germanium device. What sort of application are you looking use it for? For high current/voltage applications, silicon is pretty much your only choice, as they can be made with very high PRV (peak reverse voltage), and higher power rating. For small-signal use, germanium diodes work best; they have low barrier potential and lower 'ON' resistance (sounds like this is what you want). Used to be, the glass diodes RS used to sell were a mixture of both types. You can tell the difference with a DMM that has a 'diode' test range; the DMM will put enough voltage across the device to foreward bias it (turn it 'on') and display the apparent resistance of the device. Germanuim devices will have a lower apparent resistance. Another way would be to apply a (low) voltage across the device with a resistor in series, and measure the voltage across the device. Of course, all diodes have some reverse leakage current, and all diodes exhibit this 'barrier potential' phenomena; the trick is to find one with a low enough 'on' resistance that will satisfy your requirements. I used to get diodes from RS to make crystal sets; in those days, I found the best ones by wiring it into the set to test it! Jeff On Tue, 22 Feb 2000 16:06:49 -0500 "Bill Sudbrink" <bill(a)chipware.com> writes: > Hi, > > Once again demonstrating my vast quantities of ignorance... > I need a diode which completely blocks current in one direction > and presents as little resistance in the other direction > as possible. I bought a fist full of little glass ones at > Radio Shack for 50 cents. On my Ohm meter, they show no > conductance in one direction and 1400KOhm the other way. > What do I need to get? RS (which is the only resource I > have available, I need them like _NOW_) has many different > kinds of diodes, ranging up to two dollars per pair. > > Thanks, > Bill Sudbrink > ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: http://dl.www.juno.com/get/tagj.

24 years, 4 months

Diode help... HELP!

by mcguire＠neurotica.com

On February 22, Bill Sudbrink wrote: > Once again demonstrating my vast quantities of ignorance... > I need a diode which completely blocks current in one direction > and presents as little resistance in the other direction > as possible. I bought a fist full of little glass ones at > Radio Shack for 50 cents. On my Ohm meter, they show no > conductance in one direction and 1400KOhm the other way. > What do I need to get? RS (which is the only resource I > have available, I need them like _NOW_) has many different > kinds of diodes, ranging up to two dollars per pair. Hmm...keep in mind that all semiconductor diodes exhibit a forward voltage drop...0.3v for germanium and 0.7v for silicon diodes. If your multimeter isn't using more than that forward voltage drop to measure that "conducting-mode" resistance, you won't get anywhere with that measurement method. -Dave McGuire

24 years, 4 months

Rejuvenating VT320 monitors?

by CLASSICCMP＠trailing-edge.com

>> issue of _Processor_ and you'll find dozens of places that sell >> replacement CRT's for terminals of just about every make. >You're lucky!. Monochrome CRTs are almost impossible to obtain in the UK >-- most places that I've tried tell me that it's not worth replacing >them. This is probably correct if the unit in question is a \pounds 50.00 >portable TV. As long as we're on this subject - are B&W TV's with screens larger than 5 inches or so still common in the UK, Europe, Russia, anywhere? It's been at least 15 years since B&W TV's with 12" or larger screens were available here in the US. You *can* still find new composite-input B&W video monitors up into the 9" or 12" size range, but these are marketed towards closed-circuit TV (i.e. security) installations and tend to be more expensive than color TV's of the same size. -- Tim Shoppa Email: shoppa(a)trailing-edge.com Trailing Edge Technology WWW: http://www.trailing-edge.com/ 7328 Bradley Blvd Voice: 301-767-5917 Bethesda, MD, USA 20817 Fax: 301-767-5927

24 years, 4 months

Information still needed for Infotron IF/65 Development System II for 65XX microprocessors and CUBIT EPROM Programming board - AIM-65 or KIM ?

by aek＠spies.com

Infotron made intellegent multiplexers, this might be a test set for that. They also made erzatz DH-11's a LONG time ago.

24 years, 4 months

The tandy TRS 80 with 4 drives (fwd)

by vcf＠siconic.com

This person has a TRS 80 that needs a new home. Unfortunately I don't know too much about it. Please contact the original sender for details. Reply-to: WADDL(a)aol.com ---------- Forwarded message ---------- Date: Thu, 17 Feb 2000 12:10:11 EST From: WADDL(a)aol.com To: vcf(a)siconic.com Subject: The tandy TRS 80 with 4 drives As far I know it is in good working order. I am in Corpus Christi, Texas Are you interested in it? Walter Dillard Sellam International Man of Intrigue and Danger ------------------------------------------------------------------------------- Looking for a six in a pile of nines... VCF Europe: April 29th & 30th, Munich, Germany VCF Los Angeles: Summer 2000 (*TENTATIVE*) VCF East: Planning in Progress See http://www.vintage.org for details!

24 years, 4 months

Simon Construction

by Innfogra＠aol.com

In a message dated 2/21/2000 9:33:13 PM Pacific Standard Time, jpl15(a)netcom.com writes: > If you have any Sense of Adventure, you might consider using > electrical distribution substation switchgear for the logic. It > would take up a little more space (maybe two acres) and use more > power, but... think of the kewl noise it would make! > My scrapper has been buying all of the electrical scrap from BPA (Bonneville Power Administration) in Vancouver, Washington for the last 10 years. If someone wanted to use electrical distribution substation switchgear for the logic it could be possible. He is shipping a container of it this week. Any interest? Paxton

24 years, 4 months

HP9114B battery pack

by ard＠p850ug1.demon.co.uk

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24 years, 4 months

Sams Photofacts

by ghldbrd＠ccp.com

I have noticed that the earlier Sams are available now on CD-ROM. Don't remember if they are direct from Howard Sams or through third-party. I'm lucky, as there are complete libraries of Photofacts available at both the downtown KC library and in Independence. Even had them in Tacoma, WA so check your local library for availability. Might be able to get them through interlibrary loan. Gary Hildebrand Amigaphile and boatanchor collector

24 years, 4 months

T.D. Systems TDL-12

by jeff.kaneko＠juno.com

On Tue, 22 Feb 2000 11:22:01 -0500 "Daniel T. Burrows" <dburrows(a)netpath.net> writes: > Good - That is the only one I have info on that is handy. Both > jumpers out (A&B) it will respond at CSR174420 vec164 The alternate add is CSR > 174400 CSR 160 with Jumper A installed. > I have had one for some time but have not taken the time to play with it. > It is SCSI but it responds at an RL add. Okay, so it emulates an RL-0x drive then. If you wanted to use an entire SCSI device as a single volume, though, you'd need a special driver for O/S you're using, right? Jeff ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: http://dl.www.juno.com/get/tagj.

24 years, 4 months

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test-drb February 2000