test-drb

test-drb@ccmp.vtda.org

101090 discussions

by ajp166＠bellatlantic.net

> >Subject: Small SBC kits for Christmas! > From: "Matt Lichtenberg" <kerobaros at gmail.com> > Date: Sat, 15 Dec 2007 08:21:28 -0600 > To: cctalk at classiccmp.org > >So, every year I like to get myself a little something; this year, I'm >probably going to be getting a new computer (outside the realms of >this list), but I'd also like to get some kind of single-board kit >that I can work on. > >I'd like something along the lines of a ZX-81 kit, although it looks >like those are selling for somewhere around $250, when you can find >one. SpareTimeGizmos' Elf 2000 kit also looks fantastic, but I don't >have an 1802 or an 1861 to use in the thing, and I'd rather not hunt >any down. (If anyone wants to get rid of theirs, though, let me know. >*grin*) The Elf200 is excellent and there is a yahoo group for it as well. Finding 1802s is generally easy. the 1861 is a different can of worms but Bob solved that with a tiny board that emulates it. See the Spare Time Gizmos site for details. No you can't have mine! >Has anyone seen any similar kits out there? They don't have to be >useful for anything, just fun to play with, and not horribly difficult >to put together. I can solder fairly well, and I'm mean with a >multimeter, but I don't have the money for my own oscilloscope; I just >use other peoples' when they're not looking. Thanks, folks! If you hunt around the net there are SBC of all sorts. Allison >~Matt

18 years, 4 months

4004 and IC history / was Re: Vintage computer photogallery

by RodSmallwood＠mail.ediconsulting.co.uk

It could be him, but its over thirty years ago and of course remember I him as he was not as he maybe now. I worked for the Terminals Product Line and sold VT100's and LA36's to resellers and OEM's in the UK. The target margin per unit may not have been reached. However the volume was so high and the economies of scale such that over all DEC made lots of profit from what became the industry standard. Rod -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Tore Sinding Bekkedal Sent: 16 December 2007 18:56 To: General Discussion: On-Topic and Off-Topic Posts Subject: RE: 4004 and IC history / was Re: Vintage computer photogallery On Thu, 2007-10-18 at 13:04 +0100, Rod Smallwood wrote: > The design of the VT100 was done by one engineer who I met but I > cannot recall his name. I believe you may be referring to Mike Leis. I snapped a photo of him at a DEC reunion at The Mill: http://gunkies.org/photos/mill/big/img_3513.jpg Amongst other things, he told me that DEC considered the VT100 to be a failure, since it never met the profit margin outlined in the project proposal. The main reason they created the VT100 was because the VT52 was quite hard to mass produce automatically. -Tore

18 years, 4 months

Homebrew Drum Computer (magnetic heads)

by ajp166＠bellatlantic.net

> >Subject: Homebrew Drum Computer (magnetic heads) > From: Robert Nansel <bnansel at bigpond.net.au> > Date: Mon, 17 Dec 2007 09:31:49 +1030 > To: cctalk at classiccmp.org > >I think I might have a whack at making R/W heads using small ferrite >cores/beads, the kind used in radio work. > >My plan is to string several cores up on a straight brass rod with a >snug fit to their I.D., then bed the whole lot in wax and remove the >rod. Next I'll use an abrasive <mumble 1> to grind a tiny V-notch >from the inside of the cores, taking care not to break through the >outer diameter. > >After removing the cores from the wax I'll wind <mumble 2> turns of ><mumble 3> gauge magnet wire on them, fixed in place with super >glue. Then I would re-bed them in more wax, this time with the coils >down and the internal notches up. The cores would be almost >completely embedded in the wax to provide strength for the fInal >step, grinding a flat very slowly from the outside until the sharp >end of the notch is exposed for each core. This makes the gap. > >I'll remove them from the wax and mount them on <mumble 4> blocks >with <mumble 5> screw adjustments. > >As for the drum part, I think I'll be best off with a disk instead, >perhaps a 14" washing machine platter and spindle from a 3000RPM ><mumble 6> Gonkulator. > >So, aside from the mumbles, does this sound like a workable plan? Ah no. the gaps have to be narrow less than .001". that hs been done two peice ferrite heads (half beads) with oe side of the magnetic circuit filled with .001" thick brass shim stock. Or you could pull the heads from a number of old floppies. The 14" platter is a good source for media. Allison >-Bobby > > >> Fri Dec 14 14:22 Gary Oliver go at ao.com said: >> >> I have a reference somewhere for a drum project from the 40s that used >> what would now be simple machine-shop procedures (assuming one had a >> small drill-mill and lathe) to fashion a small drum of a few k-bit >> capacity. I'll try to dig that out and send it along. I was sort of >> planning to do something along this line myself at some point during >> "retirement" (which won't be for a few years, I suspect.) I've >> acquired >> a few of the components for fabricating the drum and will give it a >> "whirl" some day. I was definitely NOT planning to make a flying head >> device and to keep it simple enough I could fabricate a few heads from >> "first principles."

18 years, 4 months

KayPro II keyboard schematic?

by ajp166＠bellatlantic.net

> >Subject: Re: KayPro II keyboard schematic? > From: ard at p850ug1.demon.co.uk (Tony Duell) > Date: Sun, 16 Dec 2007 22:17:22 +0000 (GMT) > To: cctalk at classiccmp.org > >> > What was used inside the Kaypro to receive the keyboard data? >> >> Z80 SIO, at least on the -II and -4. > >Drat! It could be async or syunc, since that chip can be configured to >handle eithr format. But I'll be t it's the former. Its async, I posted it was Async, SIO/DART yesterday. It's levels are TTL to save RS232 conversion and power needed for negative supply. It's an easy keyboard to talk to via serial. I have two Kaypros and a spare keyboard. its not rocket science. Allsion > >-tony

18 years, 4 months

Homebrew Drum Computer (magnetic heads)

by bnansel＠bigpond.net.au

I think I might have a whack at making R/W heads using small ferrite cores/beads, the kind used in radio work. My plan is to string several cores up on a straight brass rod with a snug fit to their I.D., then bed the whole lot in wax and remove the rod. Next I'll use an abrasive <mumble 1> to grind a tiny V-notch >from the inside of the cores, taking care not to break through the outer diameter. After removing the cores from the wax I'll wind <mumble 2> turns of <mumble 3> gauge magnet wire on them, fixed in place with super glue. Then I would re-bed them in more wax, this time with the coils down and the internal notches up. The cores would be almost completely embedded in the wax to provide strength for the fInal step, grinding a flat very slowly from the outside until the sharp end of the notch is exposed for each core. This makes the gap. I'll remove them from the wax and mount them on <mumble 4> blocks with <mumble 5> screw adjustments. As for the drum part, I think I'll be best off with a disk instead, perhaps a 14" washing machine platter and spindle from a 3000RPM <mumble 6> Gonkulator. So, aside from the mumbles, does this sound like a workable plan? -Bobby > Fri Dec 14 14:22 Gary Oliver go at ao.com said: > > I have a reference somewhere for a drum project from the 40s that used > what would now be simple machine-shop procedures (assuming one had a > small drill-mill and lathe) to fashion a small drum of a few k-bit > capacity. I'll try to dig that out and send it along. I was sort of > planning to do something along this line myself at some point during > "retirement" (which won't be for a few years, I suspect.) I've > acquired > a few of the components for fabricating the drum and will give it a > "whirl" some day. I was definitely NOT planning to make a flying head > device and to keep it simple enough I could fabricate a few heads from > "first principles."

18 years, 4 months

xt/370 e-mail problem and stacked memory chips illustrated

by michaelryan＠mindspring.com

I have added a few new pictures to the xt/370 web site showing the stacked (and non-stacked) versions of the MCM66128L20, as well as two other examples of IBM engineering that employed stacked chips (AT motherboard and PC memory card) in the early 1980's. There are 36 pairs on the AT board to get 512K and 18 pairs on the memory card to get 64K. Obviously, these chips have different pinouts (at least select). The url is:- www.xt370.net click on the link to the left, 'Memory Technology' The question a data sheet might answer is:- does one of the new MCM66128L20 parts replace one of the old stacked pairs? --- also: -- >Subject: Re: Someone in search of XT/370 software >To: "General Discussion: On-Topic Posts Only" <cctech at classiccmp.org> >He's on the list. I have at least some of VM/PC, but when I tried to >email him to let him know, I got an autoresponse from a white-list >agent, which sent me to an unresponsive URL. It was sufficiently >irritating that I figured it wasn't worth pursuing further. >Seriously, folks, if you're going to ask for help, don't make it >impossible for people to give. >ok >bear Bear's criticism is well-founded. I believe I have corrected the problem; I did receive the e-mails and have responded off-list. At any rate, I greatly appreciate the interest and am sorry for the inconvenience. Mike

18 years, 4 months

Homebrew Drum Computer

by ajp166＠bellatlantic.net

> >Subject: Re: Homebrew Drum Computer > From: ard at p850ug1.demon.co.uk (Tony Duell) > Date: Sat, 15 Dec 2007 23:29:12 +0000 (GMT) > To: cctalk at classiccmp.org > >> >> I thought of this, too. So far I haven't found an online source of >> them (Google search terms: "glass delay line" OR "quartz delay line" >> OR "ultrasonic delay line" TV PAL OR NTSC). > >I didn't think the NTSC system used a delay line at the receiver, but I >must admit I've never repaired a US TV set. Yes they did/do but is was not ultrasonic. The common ones were basically the same as LONG (4.5us?) transmission lines. They would be hard to find. Allison >It's not a common component for spares companies to stock, simply because >it rarely fails. And of course more modern TVs used IC delay lines, which >are not what we want here. > >When I wanted one, I went to an (alas long-gone) TV repair shop that also >sold compoennts. No, they didn't keep them in stock, but the owner found >a scrap PCB with a delay line on it. Needless to say that was acceptable. > >-tony

18 years, 4 months

KayPro II keyboard schematic?

by ajp166＠bellatlantic.net

> >Subject: KayPro II keyboard schematic? > From: "Andrew Lynch" <lynchaj at yahoo.com> > Date: Thu, 13 Dec 2007 21:55:51 -0500 > To: <cctalk at classiccmp.org> > >Hi, >I recently bought a KayPro II keyboard. It contains a nice Keytronics >mechanical keyboard and really nice case. I'd like to convert it to a >parallel ASCII keyboard or just reuse its case but was wondering if anyone >had the schematics? > >Please let me know if you have the KapPro II keyboard schematics. Thanks! It has an 8048 uP if memory serves and the output is TTL level serial ASCII. Making it put out parallel would be a major hackup including reprogramming an 8748. Allison >Andrew Lynch

18 years, 4 months

Quick survey

by cclist＠sydex.com

On 16 Dec 2007 at 9:06 dwight elvey <dkelvey at hotmail.com> > These are all 5.25inch. As far as I know, 10 sectored was > the most common. I don't know of any that used 16 sectored > and never heard of 9 sectored. The Vector Graphic systems all used 16-sector media and I've seen a few others systems as well. So, I'd be safe by generalizing that 8" 32-sector and 5.25" 10- and 16-sector covers just about all of the hard-sector media in common use? Does anyone know of any other "common" 8" hard-sector media? Thanks, Chuck

18 years, 4 months

Small SBC kits for Christmas!

by cclist＠sydex.com

From: "Matt Lichtenberg" <kerobaros at gmail.com> Date: Sat, 15 Dec 2007 08:21:28 -0600 While not vintage (but then, is any modern kit really "vintage"?), TI has a very slick and inexpensive gizmo for their MSP-430 16-bit microcontroller. $20 bucks for a USB stick including programmer and processor; $10 for additional uC "heads". Might be a kick to fool around with: http://focus.ti.com/docs/toolsw/folders/print/ez430-f2013.html Cheers, Chuck

18 years, 4 months

cctalk Digest, Vol 52, Issue 32

by cclist＠sydex.com

On Sat, 15 Dec 2007 10:36:39 +0100 (CET) > From: Christian Corti <cc at corti-net.de> > All the drums that I have seen have fixed heads. There are adjusting > screws for the distance between head and surface, but the head itself is > then fixed with another screw after adjusting (we had to do this on the > drum of our second LGP-30). Univac made extensive use of flying head drums during the 1960's. Systems as late as the 1108 used them. AFAIK, they all had "FH" prefixes to identify them as such. Bitsavers has the manual on the one I used on the 1108, the FH-880: http://www.bitsavers.org/pdf/univac/1107/UT-2560_FH- 880_Drum_Dec61.pdf IIRC, the FH-880 spun quite fast. On the other hand, the "big drum" on the 1108, the FASTRAND II, was a slow sewer-pipe of a monster. Here's a document that accurately describes it: http://www.fourmilab.ch/documents/univac/fastrand.html IIRC, the head movement was accomplished through an system of levers connected to solenoids that directly converted a binary code to a physical position. Regarding magnetostrictive delay line, bitsavers also has a collection of PB250 documents that might be worth a perusal: http://www.bitsavers.org/pdf/packardBell/PB-250/ Hope this helps, Chuck

18 years, 4 months

Homebrew Drum Computer Delay Lines

by dkelvey＠hotmail.com

> From: bnansel at bigpond.net.au > > I've come across a reference to a reverb unit made with a garden > hose, speaker, and microphone. Would something as bone-headed as > this work as a data delay line? > > I've read that mercury was used in delay lines because it was a > better impedance match with quartz transducers, but wouldn't water > work nearly as well? Everything would need to be kept at a constant > temperature, and no doubt there would be some dispersion of the > compression waves. It's my understanding that a lot of materials > were tried for delay lines, but that mercury was the "best." > Hi The primary reason for mercury was the slow propagation time, not impedance. The slower, the more bits per length. Mechanical transformers are not all that hard to create. Early programmable calculators use a different mode of transmission. They use rotation of a wire. The twisting goes slower along the wire than a compression wave because it is the rotational inertia compared to the spring of the wire. Compressional waves tend to travel faster. In something like mercury, being a fluid, can only transmit compressional waves ( except other surface waves like ocean waves ). A wire can use either compressional or rotational. The rotational is slower and can hold more date for distance. The important thing for any of these is absorbing any reflection. This means that impedance matching and possible dampening will make all the difference. Surface can have vertical as well as shear waves but these are harder to control. The rotational wave is similar to a shear wave. Dwight _________________________________________________________________ Get the power of Windows + Web with the new Windows Live. http://www.windowslive.com?ocid=TXT_TAGHM_Wave2_powerofwindows_122007

18 years, 4 months

any idea how to find old diamond edge 3d card?

by brad＠heeltoe.com

can anyone point me to a place to find an old "diamond edge 3d" graphics card? I specifically want one with the sega controller ports and a copy of virtua fighter. I looked on ebay - no luck. anyone have any ideas? any good places for ancient (like 1995) graphics cards? -brad

18 years, 4 months

4004 and IC history / was Re: Vintage computer photogallery

by RodSmallwood＠mail.ediconsulting.co.uk

My memory may be at fault here but that sounds like it. A quad board ... I can't recall any yellow handles. It did have the standard DEC 20mA ASR 33 conector on a bit of short grey cable hanging off the top of the board. Other early sightings at DEC VT100 prototype . Wire wrap board mounted on a piece of thick plywood. Another similar bit of plywood on top with the monitor out of a VT52 perched on it. A third bit of plywood held the keyboard. A PSU (I know not whence that came) and an Intel MDS. (8 inch Floppy based in a blue box.) So I asked the inevitable 'Why all the wood' 'It doesn't short anything out came the reply' The design of the VT100 was done by one engineer who I met but I cannot recall his name. The case was the work of an industrial designer. We all thought the case was really smart LA36 prototype another wirewrap wonder with the print mech screwed to a board. LA180 prototype as LA-36 but with the wooden board clamped to the bench to stop it leaping about. Rod Smallwood -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of William Donzelli Sent: 18 October 2007 04:12 To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: 4004 and IC history / was Re: Vintage computer photogallery > I'm sure I saw a development system at DEC for the 4004 running on a PDP-8 circa 1975. I think in its collection, RCS has a DEC Y187 card (the only yellow handled Flip Chip I have ever seen) that has a 4004 on it. -- Will

18 years, 4 months

"Requiem for the Mainframe" on CBC-Radio, 4 PM Saturday

by hilpert＠cs.ubc.ca

Brief notification, but I just heard a blurb announcing as per the subject line, for those who happen to be near the radio in the next hour and can tune in the CBC (after the news at 4). (It's on the show "SPARK", if one wishes to try to hear a repeat.) It is about the mainframe computer, but that's all I got ... can't testify further as to the content.

18 years, 4 months

Quick survey

by dm561＠torfree.net

Date: Sat, 15 Dec 2007 17:53:16 -0800 From: dwight elvey <dkelvey at hotmail.com> Subject: RE: Quick survey <snip> >Hi > There is nothing in the drive that is specific to the number >of sectors. ------- Except that a number of "modern" drives will not go ready and pass data with any hard sector disks. ------ > The following were 10 sector disk: >Polymorphic 8813 Used both single and double density disk >H8/89 H17 controller used single density >NorthStar single density ( double?? don't think so ) > These are all 5.25inch. As far as I know, 10 sectored was >the most common. I don't know of any that used 16 sectored >and never heard of 9 sectored. >Dwight -------- Just goes to show ya: all I've got are 16 sector disks, originally used in CBM computers (not because they were needed but because they were cheap) and now handy for my Vector Graphic MZs. I think Jerome was talking about 9 sector soft sector disks. mike

18 years, 4 months

digital camera capabilities

by rdawson16＠hotmail.com

As an expert in this area, my opinion is that silicon sensors have a long ways to catch up to film. Both CCD and CMOS sensors lack in resolution and the spatial sampling artifacts Der Mouse mentioned are only part of the problem. (CFA array, metal shading of the cell) The world however, is focused (hahah pun intended) on the megapixel wars. Far more important is the geometry of the color filter array and conductors at the periphery, causing viginetting. Also, the conversion of the A/D in both systems is only 12 bits, far below the dynamic range of film and the eye. While at Micron, we developed a high dynamic range sensor for the security camera market, by varying the cell precharge and a sub ranging A/D for the sample. Imagine a security camera viewing a dark face in the lobby, and the security cam looking outside the front door glass at the daylight street too, we could image both of these simultaneously, no f stop changes... Lucas Film Pioneered the OpenEXR high dynamic range format: http://www.openexr.com/ Also take a look at where film is with the Gigapixel project: http://www.gigapxl.org/ Film has a few miles left for sure. Randy > From: mouse at rodents.montreal.qc.ca > Date: Sun, 16 Dec 2007 11:03:30 -0500 > To: cctalk at classiccmp.org > Subject: Re: digital camera capabilities / was Re: 1000+ old computer in > > > The effective resolution of 35mm film is IIRC considered by > > professionals to be in the 27MP range; DSLRs are rapidly approaching > > this. > > Perhaps - but film still has attributes which digital cameras don't, > such as lack of aliasing artifacts (because the grains are randomly > dispersed in the film instead of being in a neat rectlinear grid). > > /~\ The ASCII der Mouse > \ / Ribbon Campaign > X Against HTML mouse at rodents.montreal.qc.ca > / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B _________________________________________________________________ Don't get caught with egg on your face. Play Chicktionary! http://club.live.com/chicktionary.aspx?icid=chick_wlhmtextlink1_dec

18 years, 4 months

Small SBC kits for Christmas!

by kerobaros＠gmail.com

So, every year I like to get myself a little something; this year, I'm probably going to be getting a new computer (outside the realms of this list), but I'd also like to get some kind of single-board kit that I can work on. I'd like something along the lines of a ZX-81 kit, although it looks like those are selling for somewhere around $250, when you can find one. SpareTimeGizmos' Elf 2000 kit also looks fantastic, but I don't have an 1802 or an 1861 to use in the thing, and I'd rather not hunt any down. (If anyone wants to get rid of theirs, though, let me know. *grin*) Has anyone seen any similar kits out there? They don't have to be useful for anything, just fun to play with, and not horribly difficult to put together. I can solder fairly well, and I'm mean with a multimeter, but I don't have the money for my own oscilloscope; I just use other peoples' when they're not looking. Thanks, folks! ~Matt

18 years, 4 months

Quick survey

by cclist＠sydex.com

Would I be more-or-less correct if I assumed that the bulk of hard- sectored diskettes in use fell into two groups: 16-sector 5.25" and 32-sector 8"? I know that there are other physical formats, but I'm wondering if that would have 90% coverage? Thanks, Chuck

18 years, 4 months

Homebrew Drum Computer

by roger.holmes＠microspot.co.uk

Your target of the technology of 1963 fits reasonably well with my 1962 mainframe, it uses drum(s) for backing storage (holding program and data overlays to be brought into core) but I don't think that makes much difference to the drum itself, other than you may want more than one read/write head per track. Each drum looks to be about a foot diameter and about a foot and a half long. They spin at 5240 rpm on a vertical axis. The drum is made of aluminium and the manufacturers (International Computers and Tabulators) had a lot of trouble getting the surface coating right, trying all sorts of high tech methods until they found the most effective method was for someone to smooth it on by hand while the drum was spun at low speed, rather like a potter throwing a clay pot. They also had problems with the length of the drum, and had to logically divide it into two sections, each one with its own timing track and datum track. Hopefully if you keep the drum length small this will not be a problem for you. The drums are powered by 3/4 horse three phase motors with V-belts providing a step UP in speed from just under 3000rpm at the motor to 5240rpm. They do not need clean room conditions, they are not sealed, and even have a fan to draw cold air up from the bottom over the surface and out the top, or is it the other way around, I can't remember, the fan are currently removed anyway and the drums run fine in a rural environment (i.e. reasonably clean air, no coal fire smoke/smog/ diesel particulates) The drum sits within an aluminium casing which holds 244 (+some spares) read/write heads arranged in a helix so they do not need to be physically close to each other. The heads do not fly, and can be moved in and out using an Allen key, which is apparently done whilst watching a pressure gauge on an airline blowing air through a venturi in the read/write head, so that when the air pressure reaches a certain level, the head must be close enough to the drum because the drum is starting to impede the air flow. The steel screws have now rusted and seized in the aluminium but work just fine because if can't work loose they can't go out of adjustment. The drum is coated rather than plated, I know this because when certain machines used by the Home Office for security purposes were decommissioned, a friend of mine was required to dismantle the drums and wash the magnetic coating off of the drums before they (the drums) were allowed to leave the premises. The machines had earlier survived being blown up by terrorists detonating a bomb on the window ledge outside one of the computer room windows. They don't make them like that any more, tough as old boots! The same friend also worked on a serial drum machine with valves which was installed at a Carbon factory where the inside of the machine used to get covered in conductive fine carbon dust. It is amazing it worked at all. Another friend worked on modern electronic weighing equipment at a phosphate factory using bird droppings as the raw material. He was called in to one machine which had stopped working the previous day, and found a small rubber grommet had failed, the chemicals had got in and eaten the resin of the PCBs and the copper tracking was hanging loose inside the cabinet, it seemed that it had somehow been working in that state for some time because it would have taken some weeks for the resin to be consumed, so maybe this contradicts my statement that they don't make them like that any more. The 1MHz main machine clock is derived from the 250KHz drum timing track, so no need to synchronise to the drum except when switching between drums, or the two halves of a drum. The machine can also be run from a separate clock, though of course all drum accesses fail. For fault finding, it can even be run one cycle for every time you press a button, wonderful to watch data shifting through the registers displayed on the front console and see where your data is getting corrupted. Not so good for fault finding the drum, magnetic tape or other peripherals though. I hope some small part of these details might be of help to you, good luck with the project.

18 years, 4 months

KayPro II keyboard schematic?

by ajp166＠bellatlantic.net

> >Subject: Re: KayPro II keyboard schematic? > From: ard at p850ug1.demon.co.uk (Tony Duell) > Date: Sat, 15 Dec 2007 23:09:21 +0000 (GMT) > To: cctalk at classiccmp.org > >> It has an 8048 uP if memory serves and the output is TTL level serial >> ASCII. Making it put out parallel would be a major hackup including >> reprogramming an 8748. > >Or alternatively converting that serial output to parallel using an >external circuit. How hard that is depends on the format of the serial >data. If it's an asynchonous signal, with start and stop bits, a 40 pin >dumb UART chip should do it. > >What was used inside the Kaypro to receive the keyboard data? Z80 DART, The keyboard is a simple TTL level serial (async) protocal. It's bidirectional for lighting leds if memory serves. Allison > >-tony

18 years, 4 months

Homebrew Drum Computer

by ajp166＠bellatlantic.net

> >Subject: Re: Homebrew Drum Computer > From: Gordon JC Pearce <gordonjcp at gjcp.net> > Date: Fri, 14 Dec 2007 10:01:09 +0000 > To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> > >On Thursday 13 December 2007 07:48:00 Robert Nansel wrote: > >> Certainly I could trash a few old cassette decks, or even get some >> floppy R/W heads to experiment with audio recording tape super-glued >> to a soda can, but I really want to get at least the performance the >> old machines could produce, so that means a reasonably fast drum RPM, >> somewhere around 6000 RPM, say. > >That's actually pretty fast, and anything you stick to the drum will need to >be stuck very firmly! By comparison, a washing machine in fast spin goes at >roughly a quarter of this speed, and a typical car engine is reaching >its "red line" at around 6000rpm... > >You would need an extremely good workshop to machine up a drum that would stay >in balance at this sort of speed. It's actually the sort of thing that you >might want to farm out to a specialist machine shop. I would be inclined to >make the drum out of a bit of thick-walled aluminium tubing, carefully bored >to remove any imperfections from the inside that might affect the balance. A >couple of aluminium end caps would take a thickish steel axle and the >bearings (which would be tricky in themselves - they'd need to be sealed to >prevent grease being thrown out, or something capable of running fairly dry >at high speed). Then you'd skim the drum to ensure it was perfectly >concentric - any runout would very quickly destroy the bearings at 6000rpm. >Some motors use little sealed ball races. I'd consider looking at teeny-tiny >taper roller bearings like car wheel bearings, so that you could use a shim >to set the preload very accurately to remove any play. I can probably >provide a scan of a car gearbox manual that shows *exactly* how to do this >bit. > >You'd probably need to balance it after painting or otherwise coating it with >some sort of magnetic material. I don't know what you'd use for that. You >could probably research what they used in early drives. I am now entering >the realms of speculation, but my gut feeling is that you'd need to somehow >spray it on and rub back the layers to get a perfectly smooth finish - when >it's done it shouldn't quite be hot-rod shiny but it should be very flat and >polished. > >Over to Tony, I think... Most of the old Drum machines spun at 1200, 1800, 3125 or maybe a screamigly fast 3600. Though 1800 is the more common. Also most used "fast tracks" that had more than one head per track radially so that a partial rotataion was needed. A good machine to study is the Minuteman Missle guidence computer. It was bit serial and used a disk as a "drum" rotating memory. Allison Allison >Gordon

18 years, 4 months

Homebrew Drum Computer

by bnansel＠bigpond.net.au

I thought of this, too. So far I haven't found an online source of them (Google search terms: "glass delay line" OR "quartz delay line" OR "ultrasonic delay line" TV PAL OR NTSC). -Bobby Fri Dec 14 19:10 Tony Duell wrote: > I wonder if you could use those glass delay lines that were used in > PAL > colour TV receiver until fairly recently (and there must be plenty > still > around)? Alas they have a somewhat odd delay time (a little less than > 64us -- one line period of the European TV signal), but I am sure you

18 years, 4 months

KayPro II keyboard schematic?

by robert.maxwell＠creationtech.com

Got a UART? It will make the Kaypro keyboard output into parallel without changing a thing. The signal's 300 baud RS-232 at TTL levels. Bob Maxwell

18 years, 4 months

Homebrew Drum Computer

by dm561＠torfree.net

Date: Sat, 15 Dec 2007 13:23:13 +1030 From: Robert Nansel <bnansel at bigpond.net.au> Subject: Homebrew Drum Computer >I thought of this, too. So far I haven't found an online source of >them (Google search terms: "glass delay line" OR "quartz delay line" >OR "ultrasonic delay line" TV PAL OR NTSC). >-Bobby Fri Dec 14 19:10 Tony Duell wrote: >> I wonder if you could use those glass delay lines that were used in >> PAL colour TV receiver until fairly recently (and there must be plenty >> still around)? Alas they have a somewhat odd delay time (a little less >> than 64us -- one line period of the European TV signal), but I am sure ----------------------- I've got some old VCR boards with 2 glass delay lines on 'em: Markings: DL BTB85B 042 (Component # DL2K0, 6cm long, 4 pins) And: ADL-FN2038M 337P16301 4003 (DL6A0, 3cm, 3 pins) Just slabs of quartz with wires attached (the covers are removeable). Might be tricky to find specs though; unfortunately no idea of the VCR make/model. Also should have an old MS delay line somewhere. mike

18 years, 4 months

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