test-drb August 2008

test-drb@ccmp.vtda.org

202 participants
323 discussions

by ajp166＠bellatlantic.net

> >Subject: Re: Wanted: vacuum tube logic circuits > From: William Blair <wbblair3 at yahoo.com> > Date: Sat, 30 Aug 2008 07:58:29 -0700 (PDT) > To: cctalk at classiccmp.org > >William Donzelli wrote: > >> I have exactly one 12U7 in stock. I have a few 12K5s, as >> well. > >I've now got a number of different dual triode tubes to try from a local electronics shop that has a large collection of tubes from former TV and radio repairmen. $1 each and they have a B&K 707 tube tester to test them on. > >> One thought about using space charge tubes for logic - they >> might end up being slow as molasses. > >>From a message above, it looks like even a 6.3V plate voltage on a standard (not low voltage) dual triode tube will work and I'm after a visibly slow (a few Hz at most) multivibrator anyway with a binary counter circuit attached. Most all of the space charge tubes were optimized for 12V plates. IF you can run 12V to 25V range you limit yourself less as even generic 12AX7s, 12ATs and 12AU7s perform serviceably there. Allison

16 years, 10 months

Subject: Re: Wanted: vacuum tube logic circuits

by ajp166＠bellatlantic.net

> >Subject: Subject: Re: Wanted: vacuum tube logic circuits > From: William Blair <wbblair3 at yahoo.com> > Date: Sat, 30 Aug 2008 07:42:53 -0700 (PDT) > To: cctalk at classiccmp.org > >Chuck Guzis wrote: > >> My first exposure to very-low plate voltage applications >> was with a code-practice oscillator built from a circuit in the ARRL >> Radio Amateur's Handbook. ISTR it used a 6SN7 that used the >> 6.3v from the heater winding as plate voltage. At any rate, it would >> drive a pair of earphones. Perhaps someone with a RAH collection >> from the 1950's might locate the circuit. > >Thank you! That's the perfect tube multivibrator lead which allowed me to find these references using "code oscillator" and "6SN7" as search terms: > >p29, Dec '55: "A Heterodyne Crystal Calibrator AND CODE PRACTICE >OSCILLATOR" uses both halves of a 7N7, 6SN7, or 12AU7 (or pairs of many triodes) and two crystals to give marker signals at the DIFFERENCE of the two crystals > >p41, Jun '52: "...Frequency Standard...Oscillator" uses a 6F6 >oscillator, both halves of a 6SN7 as a multivibrator > >p30, Mar '62: Uses a 6AU6 oscillator at 100 kc and a 12AU7 >multivibrator to also give 50 kc markers > >p33, Jan '65: Uses a 6AQ5 oscillator at 100 kc and a 6AS6 10-kc >sub-harmonic generator (no diode and NO inductors!) > >p34, May '65: Uses a 6AU6 oscillator at 100 kc, a 12AU7 multi- >vibrator for 10 kc points, and another 12AU7 > >All of these and more were found here: > >http://newsgroups.derkeiler.com/Archive/Rec/rec.radio.amateur.homebrew/2007… > >Do you recall if the p29, Dec '55 project was the 6.3V plate voltage project you mentioned? > >The successful use of 6.3V as the plate voltage in a multivibrator using a standard HV tube is extremely encouraging. The lowest voltage used for the audio circuits I've built was 24V which was most likely used to put the tubes in a more linear operating region which wouldn't be necessary with a multivibrator. > >> While dual (identical) pentodes aren't too common for >> you to use the first grid as a space-charge element, >> I wonder if one of the sync-separator tubes, such as the >> 6BU8 might not do the trick. Single cathode and first grid, >> independent 3rd grids and plates. > >Thanks, that will be an interesting thing to try. > >> In the 20's and 30's before small-geometry power >> tubes became available, "microwave" experimenters would take a >> hefty triode and put a high positive voltage on the grid and a >> slightly negative voltage on the plate to induce Barkhausen >> oscillation. But that has nothing to do with your problem, so >> forget that I mentioned > >But thanks for mentioning it anyway since I'm interested in reading about any unusual operating modes for tubes. > >Bill I just got finished builting a recieving converter and used 12V as Plate voltage with good success using standard 12BA6 for RF amp, mixer and osc functions as I couldn't find my supply of 12EK7s. The 12BA6 nominally is speced at 150V for plate. The assumption is that triode tube are required for logic is also false. If the goal is to stay away from scary voltages I'd suggest 22.5, 45 or 67V as they are easy to obtain and most any tube performs resonably in that range. Running below 12V is harder and narrows ones choices. Allison

16 years, 10 months

Looking for DTC520 schematic, etc.

by oldcpu2＠rogerwilco.org

[Repost, now that the list is back up... (Thanks, Jay!)] My old Novell 2010 CP/M computer[1] has suffered a failure in the Data Technologies Corp. DTC520 controller. IIRC, this controller can support up to 2 MFM/ST506/ST412 drives and 4 floppies. In my case it's only hooked up to a single Seagate ST-506 (5MB! Woohoo!), and a single Shugart SA450 5-1/4" floppy. Apparently this controller was not too uncommon in the day. In my case, the DTC520 is installed in the disk subsystem that's separate from the main terminal/computer, and they no longer will talk to each other. The problem seems to be related to the section that handles the IO between this controller and the CPU box. I've replaced one chip (74LS33) that was showing some serious corrosion on the pins/legs, thinking that maybe some of that had migrated into the IC die itself, but no change in behavior. It's still indicating a screwy logic level on one of the gates, but it must be coming in on the inputs. I need a schematic to help me trace the signals. I can't locate anything online. Does anyone have anything that could help me out...schematics, technical description, etc.? Many thanks. - Jared [1] Before there was Novell, Inc., the networking software company, there was Novell Data Systems (NDS), c. 1979. They had the big idea of creating a "Data Management Computer" (DMC) around a 68000, which acted as a micro-mini-mainframe for up to 24 intelligent terminals. While this project never really got off the drawing board, around 1980 NDS added (yet) another CPU to their intelligent terminal and stuck CP/M 2.2 on it. They sold a handful of these (I ended up with one) in an effort to generate a little cash flow while the 'real' project of the DMC was still in works. In the end, it was all a little too late and NDS collapsed in the latter half of 1982. It was at this point that Ray Noorda was recruited to revive the company, and in January 1983, Novell, Inc. was (re)born with the focus of networking primarily IBM PCs. The DMC, by the way, ended up becoming a file server (as opposed to Corvus', 3Com's, et al, 'disk (slice) server' technology) and the rest is history. Later, around 1988, Novell, Inc. dropped all hardware products to focus exclusively on their NetWare software.

16 years, 10 months

Schematics of Atanasoff-Berry Computer logic circuits?

by ed＠ed-thelen.org

> Message: 8 > Date: Fri, 29 Aug 2008 13:47:07 -0800 > From: Brent Hilpert <hilpert at cs.ubc.ca> > Subject: Re: Schematics of Atanasoff-Berry Computer logic circuits? > To: General at invalid.domain, "Discussion at invalid.domain":On-Topic and > Off-Topic Posts <cctalk at classiccmp.org> > Message-ID: <48B86E5B.C9A63D91 at cs.ubc.ca> > Content-Type: text/plain; charset=us-ascii > > William Donzelli wrote: >> >> > I think, rather, that that's a good portion of the explanation of why they >> > were so slow. >> > Ballpark example, take a 12AU7: the sum of the grid-to-plate and >> > grid-to-cathode capacitance is around 3 pF. Suppose the network resistance >> > feeding the grid circuit is 250 KOhm, that's an RC time constant of 0.75uS, >> > a little better than just 1 MHz. (R can be reduced of course but power >> > consumption is then on the climb.) >> >> Well, OK, i could buy that, but from what I have seen from the >> circuits and construction of tube logic circuits is that the 3 pF is >> not much compared to all the stray capacitance kicking around due to >> construction techniques. > > I'd say point-to-point wiring becomes problematic when you start getting going > into the higher shortwave / low VHF, and granted it becomes an issue in a > physically large system, but it may not be bad as you might think. The 10MHz > stage of the HP 524 counter is done with 'rats-nest' point to point wiring with > components on tag boards separated by wires from the tube sockets, even for the > grid circuits. The key was they went to high-frequency pentodes instead of > duo-triodes, low-R circuits, diode clamps, 1% resistors: hi-speed was > 'possible' but very expensive to accomplish. > Looking up the plate to grid Direct Interelectrode Capacitance, grid to plate is 1.5 pf However , the Miller effect makes that quite interesting - depending on the effective stage gain, the effective capacity is increased by the effective stage gain - which is a big frequency limiting (and stability) factor - basically why pentodes and tetrodes were developed, (reduce the Miller effect and move the cut-off frequency up a way. The grid to plate capacitance (and the accompaning Miller effect) make trying to get stability in a tuned plate, tuned grid circuit "interesting". (Interesting enough with proper tetrodes ;-)) I ain't a curcuits guy, but remember stuff, the wrong stuff - Ed Thelen

16 years, 10 months

HUGE amount of documentation - FREE

by timdeaton＠yahoo.com

I have documentation on terminals, monitors, motherboards, add-in cards and all kinds of stuff I collected over 20 years of systems integration work (1977-1997). FAR too much to list or categorize. About 300# I do not want to see it go to waste. Anyone who will make a good home for it can have it at no cost other than you have to come get it or arrange to have it picked up. Located in Shelbyville, Indiana (Indianapolis SMSA) PLEASE come get this and give it a good home. I am long retired and need my basement office space! I have already give away TRUCKLOADS of hardware and software...all that remains is this documentation. Tim Deaton

16 years, 10 months

HUGE amount of documentation - FREE

by timdeaton＠yahoo.com

16 years, 10 months

Wanted: vacuum tube logic circuits

by wbblair3＠yahoo.com

William Donzelli wrote: > I have exactly one 12U7 in stock. I have a few > 12K5s, as well. > > > > I've now got a number of different dual triode > tubes to try from a local electronics shop that has a large > collection of tubes from former TV and radio repairmen. $1 > each and they have a B&K 707 tube tester to test them > on. > > Well, in case you wanted proper space charge tubes for your > digital logic experiments. Oh, now I understand, thanks. Well, there were a few space charge tubes in their $1 bin and they had six of the coveted (for audio) and relatively rare new old stock 6GM8s in their new tube section that they sold me for $3.75 each (they didn't know what they had) which was their cost in the 70s. They were trying to clear out their extensive new tube inventory of types that they hadn't sold for quite some time. With a car radio tube like the 6GM8 that is now of interest primarily to tube audio hobbyists, I can see why they hadn't sold one in a _long_ time.

16 years, 10 months

Unusual altair front panel...

by cctalk＠solivant.com

>> Bill Sudbrink wrote: >>> >>> I've never seen an altair with a front panel like >>> the one on ebay item #160276656912. Has anyone else? >>> Is is located close to where I work and I'm thinking >>> of asking the seller if I can stop by and have a look. >>> If it's nothing unusual, I won't bother. >> >> Nobody has an opinion on this??? Or is everybody about to >> snipe the auction? >> > I think it is interesting... > > Looks to me like an original Altair that was styled in what I call the > third generation of Altairs.. Which included the version with a simplified > front panel. > > George Rachor > Hillsboro, Oregon > If you look closely at some of the internal pictures, you'll notice that the card support rails are unusual for an 8800, too. Geoff Harrison.

16 years, 10 months

Schematics of Atanasoff-Berry Computer logic circuits?

by wbblair3＠yahoo.com

Chuck Guzis wrote: > Were these the special "space charge" tubes? > e.g. 12J8, 12U7, 12DK7, 12DL8, 12CX6, 12DE8, 12CN5, 12BL6, 12DS7, > 12AC6, 12AD6, 12AE6, 12AE7, 12AF6, 12AJ6 or 12AL8 (I've probably > left out a few)? Yes, that's some of them. There were 41 types.

16 years, 10 months

Wanted: vacuum tube logic circuits

by wbblair3＠yahoo.com

Over time, I've seen an occasional link here to an on-line copy of some 50's or early 60's electronic hobbyist magazine describing a binary project of one kind or another using vacuum tubes. If you have such a link or know of any bibliographical references to such articles that might be useful in obtaining a hard copy of the applicable articles via library-based research and inter-library loans, please post it here. I have in the past found plenty of relay-based logic circuits on-line but am having a really tough time finding any binary tube circuits with component values. If there's enough material submitted to justify it, I might start a web page on this topic or, at least, a blog that links to the relevant materials on-line. Thanks.

16 years, 10 months

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test-drb August 2008