test-drb August 2010

test-drb@ccmp.vtda.org

161 participants
220 discussions

by ard＠p850ug1.demon.co.uk

When you are cleaning up and restoring a piece of classic computer hardware, would you correct any minor mistakes made in the original production? I have a particular exmaple in mind. In bits on myu bench at the moment is an HP2623 graphics terminal This was HP's response to the well-knwon Tektronix terminals, it is, however a raster scanned device. But it has a little state machine (or parhapes you could call it a very simple procesosr) to speed up line drawing. But wanyway... On the video monitor PCB (HP call it the 'Sweep' PCB), there is a 74LS221 dual monostable chip in the common HP horixontal drive circuit, The first half of the chip delays the sync pulse (and the delay time is controlled by the horizontal centering control), the second half is triggered from that and provides a pulse of known width to the horizontal drive transistor. But I digress. You don't need to know any of that... WHile cleaning the dirt off this PCB (HV attracts dust electrostatcally, of couse), I noticed that the ground pin of this IC never made it through the board. It's folded under the package, but has been effectively surface-mount soldered to the pad when the board was wave-soldered. It works, but I can't beeleive it's as good as a proper through-hole connection, and it's certian;y not what was intended. I could trivially desolder the IC, straighten the pin, and solder it back properly. But should I? What would others do? -tony

13 years, 8 months

The reconstruction of the Konrad Zuse computing machine Z3

by wbblair3＠yahoo.com

Video link of the unit in operation at bottom of page: http://www.zib.de/zuse/Inhalt/Rep/Z3/Z3Rep/index.html Google translation: http://translate.google.com/translate?hl=en&sl=de&tl=en&u=http%3A%2F%2Fwww.…

13 years, 8 months

OT : The new Big Trak

by ard＠p850ug1.demon.co.uk

This is off-tipic for 2 main reasons : (1) the device in question is not even 1 year old yet and (2) it's not a computer. But I suspect many people here rememebr the MB Big Trak programmable toy tank from the early 1980s, and may even rememebr the Circuit Cellar article that involved modifying one. So anyway... You can buy a modrn version of the Big Trak in the UK now. To the user it's much the same as the origianl version (I will mention differences) later. Inside it's very different. The cheapest I've found it in a shop is \pounds 34.00 in Hawkin's Bazaar. I've sene it for a few 10's of pence cheapr on the web, but then youy have to add shipping. Anyway, I am sure you know what I did to mine first, even before puttign the batteryies in and trying it out.Yes, I took it apart. Given that many people here are like me, I;ll explain how to do that. 1) Remove the battery cover (2 screws) and batteris if you have fitted them. 2) Next take off the plastic strips joining the front and rear axles. There are held on by 2 scres each (self-tapping screws with integral washers). If you have put the optional stickers on, you have to peel them off to get to these screws.. Then slide off the front and rear wheels. the centre 9driving) wheels are held on to the gearbox output shaftes hy a cetnre screw. Take these off next. 3) The next bit is non-obvious and had me puzzles for a minute or so. At he back of the lower body thre's a gey plastic part the only purpose of which is to hide a coupleof fixing screws. It's held in place by 4 plastic 'barbs', one each side and 2 along the rear endge. Carefully free it and slide it out downards. 4) Ondo the tiny screw thus revealed. Ths holds the kybaord bezel in plaec on top. Carefully unclip the bezel. On the underside of it is a little pCB carrying the power switch and the IR (?) LED for the trailer interfae. Undo the fixing screw, free the PCB amd set the bezel aside. 5) Back on the uinderside undo the dozen or so screws that hold the upper body in palce. Put the Big Trak the right way up and carfully lift off the upper bod. It's still linked by the flexiprint from the keybaord. This is not pluged in, it's clamped agianst the control PCB by a plastic clamp. Undo the 2 screws and lift of the clamp, then lift the kayboard tail over the pillers. The upper body is not free, 6) Undo the 2 screws holdign the LED holder for the 'photon cannon' in palce. This alos releases the loudspeaker which is lightly glued in place under it. Free that too. 7) I should have deoslderesd the battery wires next, otherwise you hve the lower body hanging on them, which is a bit of a pain. But I didn't. Anyway, undo th 4 screws on the bottom of the gearbox. Remove the gearbox complete with the control PCB downwards. The front axle is now free, don't loose it. 8) It appears that the PCB can be removed by desoldering the motor connectios (ML+, ML-, MR+. MR-) and then taking out the 4 corner screws. I have not done this. 9) The gearbox is held together by 5 screws on top (and can be dismantled with the PCB in palce). Take these out, turn the gearbox over, andlift off the cover. You can now see all the gearing. When reasbmbling note that there are several sies of selt-tapping screwn. Don't get them in the wrong holes... OK, diffeernces from the origianl version It runs everyting (logic and motors) off a single 4.5V supply (3 D cells in series) ratehr than +/-3V (4 D cells) and 9V (pp3) of the original version The 'photon cannon' is now an LED (blue I susepct) not a filament lamp The interface to the trailer is another LED (IR?) not a jack socket. The cotnroller bvoard is totrally redesigned. There are 2 ICs. These are epxoy-capped chip-on-board devices iwth a difference. They are not on the main PCB, they are on little daugherboards which are then soldered to the main PCB. The only think on the daughterboard is the epoxy-capped chip. So in theory they can be replaced. The larger IC is clearly a microcontroller (but not the TMS1000 of the origjnal one) in a package which looks to have the smae footprintas a PLCC device, I am not sure what the smaller IC is yet. Also on the PCB are a fair number of transsitors, R's and Cs, etc. Mostly SMD devices. The gearbox is redeisgned too. It's a lot easier to take apart and reassmeble than the orignal one. The magnetic clutch between the 2 motors is still there. The optical feedback from the gearbox is still there too. In fact there are now 2 IR light bariers, one for each motor, senmsing slots in the next-to-last gear in the train. I beelive the origianl version only had one light barrier. For a fairly cheap toy it's well made. It can be taken apart and put together again withut damage. Most of it is held together by self-tapping screws, but the battery cover (which the average owner has to remvoe and rrfit serveral times( is held on by machien screws going into tapped inserts in the lower body. Nice!. I may well do a Circuit Cellar style modification to mine (that is, a serial interfce thart simulates keypresses. Or maybe repaec the microcontroller totally. -tony

13 years, 8 months

Simulated telephone

by scheefj＠netscape.net

Hello all, I would like to play^H^H^H^H use some of my vintage portables the way they were intended. For example, the Radio Shack Model 100 and the HP 110 Portable have 300bps internal modems. I have several other modems thru which these machines could talk to a *NIX but I do not want to pay for multiple phone lines in my home. How can I simulate a POTS connection between these modems? I don't need a dial tone or ringing, etc., as I can just tell one machine to connect and the other to answer. Way back I heard that a few modems would work if the tip and ring wires of the modems were crossed and connected, but most need something more than that. Is there some simple circuit I could build? Surely I'm not the first to want to avoid phone bills for such play^H^H^H^H testing. Jim

13 years, 8 months

Meet a Zuse Z23

by jkunz＠unixag-kl.fh-kl.de

Hi. This week I had the pleasure to visit a Zuse Z23 on display in my city. The Z23 is a first generation, discrete transistor and diode logic, drum based machine with a small "cache" of core memory. It is hosted at the Fraunhofer Institute for Experimental Software Engineering. Here is the Press release regarding the Zuse machine: http://www.iese.fraunhofer.de/de/presse/current_releases/PM-2010-16-210610z… Ohh, if you can't read german (at all we are talking about a german computer ;-) ) here is the english version: http://www.iese.fraunhofer.de/press/current_releases/PM-2010-16-210610z23.j… I took some pictures: http://www.unixag-kl.fh-kl.de/~jkunz/bilder/Zuse_Z23/ The machine is in very good, but not working condition. I suspect it would be a huge task to make it operable again, like the PDP-1 restoration. But it could be done. There is a complete set of documentation, schematics, some spare parts, ... A former user of that machine from the local university explained the machine and its inner workings in detail to us. In one word: Fascinating! :-) BTW: There is a tube based Zuse Z22 in working condition on display in the ZKM museum in Karlsruhe (Germany). The Z23 is kind of a transistor reimplementation of the Z22: http://www.zkm.de/algorithmische-revolution/index.php?module=pagemaster&PAG… Pictures only in the german version: http://www.zkm.de/algorithmische-revolution/index.php?module=pagemaster&PAG… -- \end{Jochen} \ref{http://www.unixag-kl.fh-kl.de/~jkunz/}

13 years, 8 months

Terminal servers (Xyplex 1600 series)

by tsw-cc＠johana.com

Help... I thought it would be "easy", just hook it up and let it go. I thought I had the proper load file (xpcsrv20.sys) in the /tftpboot directory. TCPDumps seemed to indicate that I should have a proper file with the last 6 digits of the MAC address. When I did that, I got the dump to indicate that something was transfering, but it looks like to petered out a ways through. It then goes into a silly arp sequence for a router in the 172.31... network while my network here is 192.168.0.. Questions: 1) What files should be in the /tftpboot directory? 2) Can I get access to the configuration through one of the serial ports (which one)? 3) Does anyone have one of these beasts "working" with a Linux host? I like to get it up and running. I seem to have LOTS of documents on this, but none seem to be of the "step-by step" variety using a Unix (Linux) as the RARP/TFTP host. I would prefer responses of list, but will read then here if you like. Yes, these things are a bit old. Nobody really uses terminal servers these days, and while 40 ports is a bit much, I do have a bunch of serial devices I'd like to connect to. It looked like this would be a nice thing to get working. Thanks, ...Tom Watson

13 years, 8 months

Stan Viet passed away

by c.murray.mccullough＠gmail.com

I look back with great fondness in how Stan was such a help in digging up historical ?facts? that I used in my book?He will truly be missed. All my blessings. Murray :)

13 years, 8 months

Burroughs core memory module <-> machine

by hilpert＠cs.ubc.ca

(I just mentioned this in the thread about Burroughs part numbers, but am putting it forth in a separate question in case it gets missed by some readers.) I have a core memory module from some Burroughs machine. It is a large plug-in PCB about 16 inches square containing address & inhibit drivers & such. Mounted to this is a near-same-size daughter-board containing the sense amplifiers and the folded planar array of cores underneath a metal shield. It is organised as 32 KWords, 20 bits wide. Any suggestions as to what machine this may have come from? The 20 bits is the raw-memory-word width, one could speculate that some of those bits were used for ECC and the machine-word-width is smaller, although I'm not sure off the top of my head whether 4 bits is enough for ECC on 16 bits (isn't it >log2(n) for 1-bit ECC on n bits?)

13 years, 8 months

OS/8 FORTRAN IV saving?

by hachti＠hachti.de

Hi, I seem to remember that it was possible to save a FORTRAN IV program together with the FRTS runtime system as a runnable .SV core image file. It seems that ADVENT does so... Any idea? (minor question: How does something like "R PROG ARGS" work?) Regards, Philipp -- http://www.hachti.de

13 years, 8 months

Burroughs core memory module <-> machine

by dm561＠torfree.net

----------------------Original Message: Date: Fri, 27 Aug 2010 00:30:24 -0700 From: Paxton Hoag <innfoclassics at gmail.com> Subject: Re: Burroughs core memory module <-> machine To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> Message-ID: <AANLkTik=GrMyH34cMQahxmPcSYoraFQ5+7bS=e2a=7dD at mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 > I have a core memory module from some Burroughs machine. It is a large > plug-in PCB about 16 inches square containing address & inhibit drivers & > such. Mounted to this is a near-same-size daughter-board containing the > sense amplifiers and the folded planar array of cores underneath a metal > shield. > > It is organised as 32 KWords, 20 bits wide. > > Any suggestions as to what machine this may have come from? > Burroughs made several successful solid state accounting machines before branching to full computers. Some of these had core memory and were made in the 1970s. ... Paxton ------------------------Reply: Indeed, specifically a few models in the E series, but those memories were *much* smaller; I think I still have one somewhere. In the transition from mechanical base10 systems to solid state binary systems some early E models used an interesting device called a "core counter" which was effectively a non-volatile IC-sized solid state magnetic divide-by-ten counter that emitted a pulse for every ten pulses in, a logically direct replacement for the mechanical cams and 10-position gears that most adding and accounting machines had been built around up till then. 32K x 20 sounds like it'd be out of a Medium or Large system (B2xxx or greater).

13 years, 8 months

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test-drb August 2010