"dwight elvey" wrote: ... I am reminded of the IBM 1620... :-) -brad

If you want to venture in to the land "Down Under" read about the EDUC-8. http://www.ljw.me.uk/educ8/

Philip Pemberton wrote: No ;-) Actually, I read this in the german edition in 1974, and Tony knew this series from elektor, so I assumed it was in the uk edition too ...

I do? That's news to me. I am not sure there _was_ Elektor in the UK in 1974... The early UK computer projects I know about are : the 'PE Champ' (that's tue UK magazine 'Practical Electronics') from 1977 (a 4040-based computer + 1702 programmer + UV eraser) ; the PE Digi-Cal from 1972 (a 4-function dsektop calculator built in TTL + a diode-matrix ROM. I don't recall any general-purpose computer built from TTL in a UK magazine. I don't know if anyone's mentioned it yet, but there was a Radio Shack book called something like 'Understanding Computers'. It was A3 in size, landscape format with a sprial binding on the top edge IIRC. Green cover. There was a design in there for a simple 'processor' with 16 locations of RAM. I suspect it could easily be built from TTL. -tony

Philip Pemberton schrieb: He probably talks about the German issue of Elektor. This started with 4 issues in 1970, and with 11 issues (i.e. the traditional July/August double issue) from 1971. I stopped reading it around 1992 - it too much follwoed the general trend of filling pages with standard microcontroller crap (often recycled industry application notes), that required some special circuit only available at their or associated stores. Having seen the nth PIC application that basically blinks a LED - what my generation built with 2 transistors, 2 capacitors, 4 resistors - is lame. For German and Dutch issues, eBay is your friend. Content is almost equivalent. -- Holger

On Jul 9, 2007, at 5:51 PM, Tony Duell wrote: Relaxation oscillators are fun. I like the UJT version as well, though UJTs are getting harder to find than they once were. I have two or three 2N2646 UJTs left. -Dave -- Dave McGuire Port Charlotte, FL

Chuck Guzis wrote: Are you sure there are there? I hear the sound of little shovels. Your diodes must be escaping err tunneling... :) I don't think I have seen tunnel diodes for sale anywhere? --- Strange how more and more transistors are needed to to do the simple things like blinking a light. ---

Hi For those that want to play with the concept of a Tunnel Diode, one can make a almost TD using two junction fets. You need a p and a n channel fet. Place them such that the sources are crossed to the gates. They will then act like a TD except that they will completely turn off as the voltage increases. For the smaller TO-92 type fets, they'll peak at around 1 to 1.5 milliamps. They will oscillate up to a couple hundred Hz. I built a FM jammer with a small trim cap, two fets, a coil, variable resistor , bypass cap and a 9 volt battery. For logic functions, they can be made into a stable two state element by stacking 2 of these. One will have the higher voltage across it while the other will have the lower voltage. If you really want them to act like a TD, place a resistor in parallel to give the final slope. It doesn't make them any better at doing fun things but is closer the a real TD. Dwight _________________________________________________________________ http://im.live.com/messenger/im/home/?source=hmtextlinkjuly07

On 9 Jul 2007 at 23:23, woodelf wrote: I doubt it--the transition seemed to be from bipolar to MOS in integrated circuits. JFETs in digital logic seem to have been bypossed. I've still got my GE tunnel diode (and SCR and Rectifier) manual. Lots of interesting circuits, but nothing that could have been constructed using other semiconductors at the time. There are some logic circuits in the book, however. Negistors, it turns out, are pretty easy to build. There's a web site that describes how to make simple ones using a sheet of galvanized steel. "Accidental" negistors by way of point-junction devices have probably been reported since the 1920s or earlier. Another 2-terminal semiconductor that I like is the diac. Can be used for relaxation oscillators, but up until a few years ago, I had one hooked in series with the line going to my answering machine. The moment the line is picked up at a phone anywhere within the house, the answering machine is electrically disconnected and doesn't interfere with the call. Also useful for building simple relaxation oscillators--and, of course, triggering triacs. Cheers, Chuck Cheers, Chuck

dwight elvey wrote: Does this mean that if we reduce the number of transistors we can go faster? Let see a PDP 8/Z(1) with current technology would be? :) I think the problem is computer design rather than the chip design -- You don't have random access memory any more & salesmen push clock speed rather than a usefull measure of computing power. (1) Zippy - 1000x faster the a PDP 8/E. Now back to thinking about how to build a homebrew CPU... Front panel or no Front panel.

Async machines have been done (PDP-6 and KA10, for example). The problem with clockless machines is that they are extremely hard to design for speed, and are prone to be glitchy and unreliable. -- Will

On Jul 10, 2007, at 1:53 PM, Jos Dreesen / Marian Capel wrote: I heard about the ARM996 about a year ago, but I wasn't aware that anyone was actually selling it commercially yet. Do you know of any implementations that are actually orderable now? -Dave -- Dave McGuire Port Charlotte, FL

On Jul 10, 2007, at 1:04 PM, woodelf wrote: Nah, even Intel has abandoned the "more megga-hurts!" marketing scheme. -Dave -- Dave McGuire Port Charlotte, FL

On 10 Jul 2007 at 10:49, Dave McGuire wrote: Sure. I'm not getting any younger. What have you got that's interesting? Cheers, Chuck

On Jul 9, 2007, at 6:54 PM, Cameron Kaiser wrote: It's an oscillator built around a capacitor and something with a breakdown voltage, a neon lamp for example. The capacitor charges slowly through a resistor at a calculable rate, and then (partially) discharges through the neon lamp quickly when its ionization threshold is reached and it conducts...then the cycle repeats. You vary the frequency of oscillation by changing the value of the charging resistor. In this manner, you can have a blinking light with one resistor, one capacitor, and (of course) a neon lamp. What's neat about it is that the blinking light is actually an active part of the oscillator, rather than just an indicator that displays the oscillator's state. -Dave -- Dave McGuire Port Charlotte, FL

On 10 Jul 2007 at 11:25, der Mouse wrote: Well, any frequency limited by the ionization time of the gas at any rate. IIRC, that's something like 20KHz. If you want to use a neon bulb (or a gas triode) as a sawtooth oscillator (one of the more useful aspects of a relaxation oscillator), you can improve the linearity of the charge ramp by using a very high 500vdc or more) supply voltage and a large series resistor. Cheers, Chuck

William Donzelli wrote: I guess they are. Looks at datasheet for the 884 dated - Jan 4,1945. But the cat's meow back then for use in low cost ( at the time ) scopes and other such equipment.

No, they are not the same tube. The basing is different. 884s are octal, 885s are UY. -- Will

You could also put a current source instead of a resistor. This can be made with either a transistor and s few resistors and diode or a jfet. Dwight _________________________________________________________________ http://liveearth.msn.com

Hi Chuck Ok, are we allowed to use a vacuum triode? Using high voltage to help linearize the saw tooth seems to be the sledge hammer method. What was it that Tektronics did with tubes to get the nice linear sweep? They did something that used a constant current to charge the capacitor. Dwight _________________________________________________________________ http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_mig…

Er, for the same reason that I mess around with old computers when there are newer and faseter machine I coulf buy? Because it's _FUN_. -tony

The higher voltage zeners have a slight negative resistance region. The cross over point between the knee breakdown and the avalanche is around 7 volts. We used to use 7.2 volt zeners as white noise genrators because these had a mixture of knee and avalanche type breakdown. If bias with a large limiting resistor and 9 volts, it would produce niece white noise to align wide bandpass amplifiers. One diode type could be used that is relatively easy to find and that is a diac. These should make a nice oscillator. One just has to have a high enough resistance to drop below the on current. Dwight _________________________________________________________________ http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_mig…

Roy J. Tellason wrote: Well I found this surfing last night. Fet + Pnp = Strange radio. http://www.schmarder.com/radios/solidstate/homodyne.htm

On 7/10/07, Dave McGuire <mcguire at neurotica.com> wrote: When I was a kid, my dad had a blinkenlights box on the bookshelf he built in college (somewhere between about 1958 and 1964) - it was a bakelite box, about 6"x9"x3", with a 3x3 grid of neon bulbs sticking out the front, and some flying-lead-mounted components on the inside, I presume nine caps and nine resistors, all of varying values, and an old snap-end radio battery (B battery?) You snapped a battery in, then the lights would blink in a random and pleasing fashion. I doubt he still has the box (I last remember it in the mid-1970s), but I wouldn't know where you could find a battery these days that could light a neon bulb - unless you wanted to gang a bunch of 9V batteries together, or make run a DC-DC converter off of some smaller value. Not a complicated circuit, but fascinating to a 7 year old. -ethan

Cameron Kaiser said: A quick look here at a few distributors here lists at least old stock availability, at a wide price range. Problem is IMHO that such old parts are not ROHS conforming; thus they are delisted, e.g. at Digikey. Farnell still offers them, at an obscene price, Reichelt in Germany here has a fair price. But UJTs are mainly one-trick ponys which is why they are primarily found in basic courses in electronics :-) They had their time in the 60s and 70s. Now that is exactly the work principle that Tony has described with his neon sawtooth oscillator: a resistor charges a capacitor in series. The load to this voltage divider is the UJT or the neon bulb which have a characteristics with a negative resistance at some point - once some peak voltage is reached resistance will drop very fast and will discharge the cap. Result is the sawtooth wave. There are other circuits with a comparable characteristic, like the PUT which is basically a SCR with an anode gate - you can make one with _parallel_ coupled PNP and NPN transistors. Or with a bit more effort you can utilize the same effect with a NIC or a gyrator. -- Dr.-Ing. Holger Veit IT-Management Fraunhofer IAIS Institut f?r Intelligente Analyse- und Informationssysteme Schloss Birlinghoven D-53757 Sankt Augustin e-mail: holger.veit at iais.fraunhofer.de Tel. +49 2241 14 2448 Fax. +49 2241 14 2342

Negative Impedance Converter? I would have thought most Network Interface Cards contained enough circuitry to flash an LED :-). The problem might be getting access to it,.as it's likely to be hidden inside large chips... A reciprocal impedance converter circuit. Basically, you connect an impedance to one side of a gyratorm, and the other side appears (to the rest of the circuit) to be 1/<that impedance>. It can make capacitors look like inductors and vice versa. You can make one using an op-amp. -tony

The one I was thinking of -- the neon bulb blinker -- is this circuit R o----------/\/\/------------+--------------+ | | | --- --- O --- C Neon Bulb | O (e.g. NE2) | --- | | o---------------------------+--------------+ The circuit depends on the fact that a neon requrires a higher voltage to strike than appears avross it once it's struck. R is chosen so that a glow discharge cannot be maintained in the neon with the current available from the supply through R alone. Waht happens is that C charges from the supply through R. When the voltage across C reaches the striking voltage of the neon, the latter strikes and discharges C until the votlage across the neon is less than the maintaining voltage. At this point the neon goes out, C starts to charge up again. This was probably the first circuit I ever built, before I went to school. I know it was before I'd learnt to solder, I built it using those 'chocolate block' terminal strips. I thin R was 1M, C was about 0.1uF. The DC supply was a 90V dry battery. -tony

On 11 Jul 2007 at 12:58, Roy J. Tellason wrote: Somewhere, online, I ran across a reproduction of an entire booklet on neon-bulb applications. I'll see if I can remember where... Cheers, Chuck

On 11 Jul 2007 at 15:06, Mike Loewen wrote: Yup, just sent the post citing this one. Cheers, Chuck

Chuck Guzis wrote: Or the reference at the top of this page: http://www.electricstuff.co.uk/oldbooks.html Neon bulb circuitry is cctech standard discussion #13 on a 10 month cycle. Neat, if you remember we were discussing doing just this on the list last year: Subject: Re: Vacuuum tube digital circuits (50 year rule) Date: Fri, 01 Sep 2006 01:08:14 -0700 From: Brent Hilpert <hilpert at cs.ubc.ca> To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> References: 1 , 2 , 3 , 4 , 5 , 6 , 7 woodelf wrote: Neat idea .. looked up the glow bulb logic manual and there is a circuit for a ring counter. Each stage requires 1 neon bulb, 1 diode, 1 resistor and 1 capacitor. So in theory one could build a 12-hour 6-digit digital clock (60Hz-line timebase) with 3*(10+6)+12=60 neon bulbs. Perhaps 61, using another bulb to square up the 60Hz line trigger. Might need amplifiers between digits. However, my understanding of neon logic is that it's great in theory, but not so much in practice. The characteristics between bulbs vary enough to make implementation awkward and the characteristics of the bulbs vary over time, leading to reliability problems. As the description of ring counters in the the manual says: "Lamps should be aged for best results and some selection may be desirable." There was a discussion about these issues for neon-lamp-memory on the list in May 2005.

You still can. They are called Krytrons, are expensive, DAMN fast, and are export controlled. Used for opening cans of sunshine. -- Will

On Wednesday 11 July 2007 21:44, William Donzelli wrote: That's a particularly amusing name for it.. Pat -- Purdue University ITAP/RCAC --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org

From: "Tony Duell" <ard at p850ug1.demon.co.uk> electrode You can also look out for tetrode thyratrons - these have an extra electrode that can be used to control the trigger point to some extent. The are available as heated and cold cathode versions. Jim.

IIRC, the very common 2D21 (EN91 in Europe) is a hot cathode tetrode xenon thyratron. -tony

I've seen these but what I was talking about was a three lead in a NE2 type package. Dwight _________________________________________________________________ http://liveearth.msn.com

Hi No, these truly looked just like a three lead NE2. The leads were inline. The center was the anode and the two outer ones were cathodes. It worked similar to the dekatron shown, although these use two transfer cathode electrodes between each digit. When biased right, only the right or the left cathode could be lit. One could steer which was lit by pulsing each. These stored state. As a note on the dekatron, these were used in some of the early HP counters. They were used as the first, or highest frequency, state of the counters. They were quite fast! Dwight _________________________________________________________________ http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_mig…

I don;t know if they ever turned up in computer applications, but there was a device called a 'Trochotron' that was used in counters and in the counter stages of DVMs, etc. It was a hot-cathode high-vacuum device, and was surronded by magnets. IIRC, there was an electron beam produced in the device which could be stepped round to one of 10 target electrodes (which could drive a nixie tube for display) Being a vacucm device, it didn't depent on the ionisation time of a gas, and was considerably faster than a Dekatron. According to an old databook I've looked it, Most dekatrons would go up to 4kHZ, with a couple of types being faster, about 20kHZ. Trochotrons wuuld go to over 1MHz Sounds more like Argon, but it would depend on the pressure, I think. -tony

It's pretty tough finding anything other than a reference or two about these beasts, but here's a Russian one: http://www.russiantubes.com/prop.php?t=4&p=15 Bau makes several references to these creatures. I can also recall them being used as switches for audio consoles. There are a couple of 1970's patents that reference them also. Cheers, Chuck

On Thursday 12 July 2007 16:35, Jim Beacon wrote: Many of these tubes are listed here: http://www.classiccmp.org/rtellason/tube.html :-) -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

Stroller wrote: Agreed. I even went looking for neons at Bletchley yesterday, but what I remembered as being boxes of them turned out to be ordinary panel lamps :-( Farnell look to sell some cheap ones though, so I might do some experimenting. I've got some Nixies gathering dust - I wanted to use them for something that wasn't a clock, but this neon one is sufficiently oddball that I'm very tempted... I'm still not up to speed with the theory, though - I can see how the ring counter operates once one tube is lit, but I'm not quite sure how the power-up initial status with only the first tube in each counter lit is arrived at... (i.e. how is it guaranteed that only one tube fires, rather than none or several? Is one tube chosen to have slightly different characteristics to the rest in the ring or something?)

On 15 Jul 2007 at 10:31, Jules Richardson wrote: Carrying this idea of old logic families to its next stage, I wonder if it would still be possible to get some "hard" ferrite toroids to implement a digital clock design in core logic? I'm not up to snuff on what's available in the small-quantity market. Cheers, Chuck

On 16 Jul 2007 at 10:31, Brent Hilpert wrote: I suppose if we wanted to stay with the general spirit of things, one could use a cold-cathode thyratron. I've seen where ordinary NE-2s are triggerd by placing the bulb in a conductive sleeve, shielding it lamp. Heaven forfend that I should use an SCR or transistor! I wonder if the clock could be derived from line frequency without much more than a few diodes. When you get a chance, do. It's very interesting--and very different Cheers, Chuck

On 16 Jul 2007 at 11:43, Peter C. Wallace wrote: I do remember seeing a bunch of NE-2s used on the pedalboard of an old Lowery organ as sort of a priority encoder--only the lowest note would sound if more than one note was pressed. I don't recall the circuit however. But it was a more-or-less full- sized pedalboard--about 30 notes or so. This does relate to old computer architectures--many electronic organs use flip-flops and the like. Cheers, Chuck

Thyratron ring counters, in conjunction with the Nixie tubes themselves (the Nixies were specially designed to be an active part of triggering the next Thyratron in the ring) in the first commercially produced electronic calculator, the Anita Mark VII/Mark VIII (the Mk7 sold in Europe for a short time, quickly superceded by the Mk8). These were small Thyratrons, about the size of a pinkie finger from the first joint to the fingertip. There were also used a small number of vacuum tubes, for specific logic elements which required inversion or buffering. The main clock phases were generated by a Dekatron (1 in the Mk8, 3 in the Mk7). There were lots of Thyratrons in this machine. The machine had a capacity of 12 digits, which meant 120 Thyratrons just for the ring counters. There were other boards full of thyratrons for various logic and clocking functions, for a total of over 200 in the machine. It is very cool to see one in operation without the cover on. The thyratrons do emit an orange glow when triggered. While doing calculations, The thyratrons rapidly zip on and off, one at a time, in the ring-counter circuits. Others seem to bounce around in differing patterns, depending on the type of operation being performed. On the subject of making a magnetic core logic clock...it might be possible, but the problem with core is that reading it is destructive. Circuitry would have to be built using a magnetic core flip-flop (which are possible using core logic gating functions) to retain the state of the read bit, and then a cycle initiated to "put the bit back". This would have to be done as each bit is read out of the core array. If it was read four bits at a time (4 planes), then you'd need 4 core flip-flops to retain the state for rewriting back into core. It's very unlikely that the direct output of the core could drive nixie tubes. The core outputs are typically very low voltage, low current pulses that require either pulse transformers, along with further amplification to make into usable logic signals, or all-transistor sense amplifiers. I suppose that some kind of core-based amplifier could be used, but it would be more like a transformer than a pure core, with a small primary winding, and a large number of secondary windings. The logic necessary to handle the timekeeping, the core memory read/modify/write cycle, and BCD-to-1 of 10 decoding to drive the Nixies would take a lot of core-based logic. I think it would be possible to do it, but you'd definitely need some transistorized circuitry for buffering, amplification, and clocking (though a free-running core-based clock generator might be possible). Many early electronic calculators utilized core memory as the main memory for the machines, though surrounded by a lot of diode/transistor logic for the rest of the machine. The core just stored the working registers. As far as I know, no calculator was ever built that utilized core for everything. Dr. An Wang (the inventor of magnetic core memory) did a lot of experimentation with core logic, and had patented it. But, IBM offered him big bucks to assume the patent, and he took the money. Later, Dr. Wang realized that he got ripped off by IBM, and vowed that he'd build a business (Wang Laboratories) that would put IBM out of business. He made a good run for it for a while, but never came even close. Rick Bensene The Old Calculator Web Museum http://oldcalculatormuseum.com

That is now how IBM felt. They paid thru the nose for the license. The also spent a large amount of money trying to get around the license before they caved. -- Will

Jim Battle wrote: I've long been critical/skeptical of that general attribution to Wang. While Wang can be said to have made contributions to the development of core memory, there were several ideas, as you suggest, that had to come together to produce a practical computer memory. I'm still of the understanding that the Forrester/Whirlwind developments produced the first practical random-access core memory of the 3D 4-wire form, the form which would be the standard for many years (and which would be why IBM had to pay MIT the bigger bucks). (It would be interesting to know when the 3-wire form/improvement was developed).

Rick Bensene wrote: Chuck was alluding to finding <what-ever> appropriate cores so I was thinking of it as being open-season on the design, not necessarily the "off-the-shelf" cores that would be used 50 years ago. The thought was carrying over from the discussion last week-or-two about core-logic and the clock drivers pumping the energy into the system. I don't see any reason it couldn't be done, in principle. The voltage may be an issue as you say, but if you're starting from scratch you could wind cores with a special output winding or use step-up puls transformers. Granted that by the time you sit down and do the design ther might be push-back from some other part of the design that makes it not worthwhile.

I wonder how he got the needed amplification? Did he use some form of magamp? Dwight _________________________________________________________________ Don't get caught with egg on your face. Play Chicktionary!? http://club.live.com/chicktionary.aspx?icid=chick_hotmailtextlink2

cool link! Hadn't stumbled across it before. ss At 09:30 AM 7/17/2007, you wrote:

Chuck Guzis schrieb: "Sexadecimal" had been already used with the Illiac before (around 53/54, see bitsavers), with even another scheme for the pseudo tetrades: 0123456789 K S N J F L, related to the 5 bit encoding of characters on a paper tape. I wonder why those obscure encodings evolved that don't assign letters and their encoding values in linear, consecutive order. -- Holger

On 17 Jul 2007 at 22:01, dwight elvey wrote: There was (never commercially deployed, AFAIK) a scheme using striplines doing much the same sort of thing with microwaves. I recall reading about it back in the 60's. There are a couple of "newly discovered" US patents on the subject, so I suppose the prior art isn't well known. At about the same time I seem to recall, there was a discussion of encoding information in the form of nuclear spin in, for example, the hydrogen nuclei in a bottle of water. The scheme is very hazy in my memory, but one of the gotchas was that it was LIFO and not random- access. Maybe someone on the list remembers more about this than I. Cheers, Chuck

---snip--- Hi Actually logic state can be if the core changes state, that is a one and if it doesn't change state, that is a zero. The direction of the cores state isn't important. This could even be in phase relation to a clock. When the clock goes hi, a change is a one while when the clock goes low, a non-change is a one. There is no reason to restore the state on each cycle. You just have to be a little more flexible on what you mean by a one or zero. Dwight _________________________________________________________________ http://liveearth.msn.com

On Monday 16 July 2007 14:43, Peter C. Wallace wrote: Lowrey used something of the sort in some of their tube models, along with some rather odd tubes. The description that comes to mind from having seen them mentioned in an old RCA Tube Manual was "Three-plate tetrode". I never did get that much of a grip on just how those circuits were supposed to function, and it's remotely possible that I might still have some service data available for one of those models, somewhere, if anybody's that interested.. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

Bob Rosenbloom wrote: the 3803's control panel has been cut out. I checked with another guy to be sure it wasn't on the other side and he pointed out the blue you see is the doors on the other side of the cabinet, with yellow hanging down being cut wiring. real shame to see this on Dovebid w/o a warning. Hope the 3420's aren't just doorstops that look nice as well. Jim

There's a book called 'Cold Cathode Tube Circuit Design' which covers all sorts of applications of these devices (and stabiliser valves, nixie tubes, dekatrons etc). I certailly rememebr a neon shift register and various logic gates. -tony

Back when I built mine, 90V batteries were still fairly easy to obtain. Nowadays, I'd probably go to the local 'pound shop' and buy 10 cheap 9V batteries and link them in series. The current drawn is so low that even cheap-n-nasty 9V batteries would last quite a time. IMHO it's cheating to use a step-up switching regulator IC. If you've got one of those, you can get a 555 timer ;-) -tony

Ethan Dicks wrote: I was thinking of the same 3D structure you were thinking. In fact, I have used a bundle of 10Ohm resistors in parallel wired to a bunch of 9V batteries in parallel to ignite a chemical fuse in a timed explosive. 90VDC shouldn't hurt you too bad, as long as your skin is dry when you tough the terminals. Peace... Sridhar

Chuck Guzis wrote: Cost. Peace... Sridhar

In the hopes of bringing this topic back to being on topic with the subject, I found this in my links just yesterday. http://www.homebrewcpu.com/links.htm I think I was looking for the home built cpu awhile ago. Rob Rob Borsuk email: rborsuk at colourfull.com Colourfull Creations Web: http://www.colourfull.com

Ease of getting them. O can get 9V (PP3/006P/6F22/whatever they're called this week) batteries almost anywhere. I don't know a UK supplier for 45V batteries (even the 22.5V ones [1] are getting hard to find). I don't fancy gettign a couple of batteries shipped acorss the Pond every time I need them ]1] Called 'Photoflash' or 'Hearing Aid' batteries in the old books. The fomrer because they were used to charage a capacitor of About 100uF to fire the old single-shot flash bulbs. The latter becuase they were used to provide the HT+ (B+) voltage for valved hearing aids. -tony

I did read of an early gas-discharge flash unit that used 8 30V batteries in series to get the high voltage [Totally useless bit of trivia. In the UK there were 2 series of these batteries : B154 (15V), B155 (22.5V), B156 (30V). These were ssqare in cross-section, the side of the square being about the same as the diameter of an AA cell. The B155 was actually about the same length as an AA cell too) B121 (15V, B122 (22.5V), B123 (30V), These were rectanglar in cross-section, width about twice the thickness. The thickness and length were about the same as the equivalent-voltage version in the other series] Certainly in the Europe, many bulb-type flashguns used 22.5V (or 15V) batteries in what was commonly called the 'battery-capacitor circuit). The simplest form was this : 3k-ish Flashbulb +----/\/\/---------+-------(X)---------+ | | | ------- | | --- | ===== 100uF-ish ------- 22.5V o ----- --- \ Shutter | | o \ contact | | | | +------------------+-------------------+ When there's no flashbulb inserted, there is no load on the battery at all, not even leakage through the capacitor. When you insert a bulb, the capacitor charges to the battery voltage through the bulb and the 3k resistor, the latter limiting the currrnet so that the bulb doesn't fire. When you take the picturem, the cynchronisation contacts in the shutter close, connecting the capacitor diresctly across the flashbulb and causing it to ignite. Some flash units had a test lamp that indicated the flashbulb was good -- that the ignition filament was intact. The normal way this was done was to connect a small lamp in series with a push switch aross the capacitor. Pressing said switch would discharge the capacitor through the test lamp, causing the latter to light briefly if the capacitor was charged. That would only happen if the flashbulb was intact. Indeed, and those were used until quite recently (say 20 years ago). I've seen a 'Sunpack' flash unit which has an extermnal PSU conenctor (connected IIRC, to the terminals of the main capacitor through a diode and limiting resisotr). Listed accessories included a mains power pack and a battery holder for a 510V battery. The advantage of this was a very quick recharge time, of course. flash yuniots), there were basically 4 tuypes of paower pack used to get the high voltage (a few hundred volts) for the flash tube : 1) Mains transformer + rectifier 2) Battery + Vibrator + transformer. The Battery was often a wet-cell lead-acid accumulator 3) HV battery 4) Transistorised oscillator + transformer (once transistors were in common use) -tony

Most did, I think. In the UK, GEC (who AFAIK are noting to do with the American GE company) sold special low-ionternal-resistance D-cells (we called them 'U2' size at the time) for this appliocation The problem with directly firing the flashbulb from the battery was that as the battery aged its internal resistance increased. In the end the bulb would fail to fire at all, but before, the lower current throug hthe ignitor fillament meant the bulb took longer to fire, messing up the synchonisation. Probably not a problem on the Speedgraphic/MPP Micropress shutters (large format focal plane shutters that took a good 1/4s to go across the film) Leica sold a flashgun which took ES cap flashbulbs or SCC (single contact small bayonet cap) with an adapter that was supplied with the unit. The original design used a special 6V dry batttery, this was quickly replaced by a holder that took 4 AA cells in series. Then there was a battery/capacitor module (22.5V battery) that fitted in place of that, making contacct with the battery terminals and the metal case of the flashgun (which was the connection between the bulb and sync contact). I've also got a SCC-cap flashgun that seems to have been designed for TLR cameras (from the bracket that came with it). It either uses a pair of C cells or a 22.5V baettery + a resisotr/capacitor module that was included with the unit. -tony

Allison wrote: The closest thing I can think of is keep your camera in top shape. So you can take plenty of pictures while disassembling and cleaning and testing. ... Now where did this extra 7400 come from and why is there black smoke ... :)

On 12/07/2007 21:21, Chuck Guzis wrote: I've bought stuff from them. They're not the cheapest, but they're not OTT, and they do have a good range. -- Pete Peter Turnbull Network Manager University of York

At 06:41 PM 7/11/2007, Chuck Guzis wrote: Hadn't heard of those: http://home.earthlink.net/~lenyr/borax.htm but they look interesting. So why do they glow? As for the original thread topic, I had wanted to chime in and point out the 90 volt vs. 5 volt comparison from the start. - John

Why notuse asynchonous vibrator (yes, I know, they malfunction all the time ;-)) Well, if you stick to the zinc-carbon 9V batteries (about the only sort you'll find at 3-for-a-pounds I think), then they're a direct descendant of the Leclanche' cell. So they're not really too-new technology -tony

Gyrocompasses. -- Will

You're buying me a new keyboard, man. They don't work so well with Mr Pibb sprayed in them. -- ------------------------------------ personal: http://www.cameronkaiser.com/ -- Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser at floodgap.com -- TRUE HEADLINE: Astronaut Takes Blame for Gas in Spacecraft -----------------

On Mon, Jul 09, 2007 at 10:51:18PM +0100, Tony Duell wrote: I can do it with just a single resistor and a (properly aged) neon bulb, on US line voltage. :) I can even control the rate of blinking using my hand and an ordinary lamp. ;) Pat -- Purdue University ITAP/RCAC --- http://www.rcac.purdue.edu/ The Computer Refuge --- http://computer-refuge.org

Holger Veit wrote: You don't have by any chance the "Elektronik Sonderheft Hardware I & II" ? They came out about end '70 beginning of '80 and had some nice stuff. Even a small CPU/Computer made just out of TTL ...