test-drb December 2004

test-drb@ccmp.vtda.org

243 participants
530 discussions

wanted ; docs for Omnibyte Corp OB68K1A multibus SBC

by list_classiccomp-tech＠greencroft.co.uk

Anyone got any info on the above board? motorola 68000 CPU, DRAM, ROM & some IO (2*6821 PIAs, 2*6850 SIOs, 1* 6840), and a bunch of switches, all on a MultiBUS I card. Also has "master/slave D16 M24 I16 VOL 1982" legended. Nothing helpfull showing up on a Google so far. (received it amongst a pile of DEC manuals & TK50s rescued a month or so ago) ta. greg

19 years, 7 months

Last chance for container to Germany

by vcf＠siconic.com

If anyone has anything they want shipped from the Silicon Valley area to Munich then please pipe up soon. Last chance... -- Sellam Ismail Vintage Computer Festival ------------------------------------------------------------------------------ International Man of Intrigue and Danger http://www.vintage.org [ Old computing resources for business || Buy/Sell/Trade Vintage Computers ] [ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]

19 years, 7 months

Anyone got an HP Paintjet printer?

by ard＠p850ug1.demon.co.uk

This is going to seem like an odd question, but here goes... I've borrowed a Paintjet (colour inkjet) printer from HPCC (as you probably all know I am somewhat invovled with that club) with the idea of taking it apart, figuring out how it works, etc. Yes, the club do know I do that sort of thing :-) So far, so good. I've figured it out, made notes, and put it back together. Problem is, I can't get it right... Here's the problem. There's what I'd call a 'pressure bail' that holds the paper against the platten. It carries a transparent plastic window. And that window seems very loose. So loose, in fact that it rubs on the ink cartridges when you move the carriage. And when the carriage moves to the far right (parking position), the window drops so far that it jams the carriage, which then can't move back to the left. The problem is compounded by the fact that I don't know that it was correct before I took it apart. I do know I've got no bits left over. I also didn't dismantle that part of the printer (I did remove the logic board and mechanism from the case, I did dismantle the mechanism far enough to remove the carriage and motors). I can't see any obvious places where something (like a spring) should go, but equally the finish on the tabs of the window (I did remove that _after_ I discovered the problem in an attempt to find it) doesn't look as good as I'd expect from old HP. Maybe some tabs have broken off. So my questions are (if you have a Paintjet, original version) Look at the windw in front of the platten on top of the machine. Does it seem to sag at the front edge, or is it forced up against the inside of the case. If you can remove the cover (I can tell you how to do this, it's easy and doesn't need tools), I'd like to know just what supports the window. Are there any springs or spring wires/leaves on the front of the pressure bail? Are there any 'extensions' to the tabs on the window at the front of the bail? If I know thrre's something missing/broken I can have a go at making/kludging it. -tony

19 years, 7 months

NCR Tower PSU again

by julesrichardsonuk＠yahoo.co.uk

Hmm, getting somewhere; found a dead triac near the input which was supposed to bypass that 10 ohm resistor that was burning out once the PSU had started up. Presumably the intention was to allow the PSU to start a little more gracefully. Nice bodge story: I just found out why the system wasn't starting up at all. It had been semi-dismantled since it had died years ago; I'd reassembled it recently when trying to get it running again. After much wiring tracing I've just discovered although the cable between the control panel and the backplane is keyed at both ends, at one end the connector was on back to front. That hadn't stopped whoever assembled it at the factory from hammering the keyed connector backwards into its socket! I hadn't noticed how bent out of shape the socket was when I reassembled the machine; I'd simply lined up the key on the connector with the relevant slot on the socket, then spent ages trying to work out why the PSU wasn't even trying to start up when the switch was operated. Grrr! Now, I'm getting a good 5.1V output, but there's a nasty wheezing noise (not a whine!) from somewhere on the main PSU board. The +12V and -12V rails are seriously up the spout. With a light load (just a couple of fans), the fans spin up for a couple of seconds before everything shuts down for a couple more seconds, then the cycle repeats (the wheezing sounds like breathing at this point!). With no load the wheezing's constant and the PSU doesn't shut down, but -12V rail is at -4V and +12V rail is at +5.3V. I'm going to load the PSU up with an (unwanted) hard disk in a moment just in case it's not firing properly because of not enough load - not sure if I want to risk any boards in there at present though, but of course it's possible the PSU's not operating properly because there's some feedback from the absent CPU board not present... Any widsom appreciated. Sure don't like that wheezing noise - cap or wound component? Fault or just something not being driven at the right frequency? cheers Jules

19 years, 7 months

Signetics 8x300 instruction set

by aek＠spies.com

> I looked under signetics and didn't see _dataSheets. it wasn't there an hour ago :-)

19 years, 7 months

8x300 subroutine call mechanism revealed

by tomj＠wps.com

Thanks Al, for giving me a retro-headache, that chip's architecture is even worse than I remembered :-) It's truly a terrible architecture. The subroutine call mechanism is a trivial software convention, you could do it on any machine that had one unit of storage to dedicate. Only 32 one-deep calls are allowed; 32 is an 8x300 limitation. The trick is that CALL and RETURN are macros. Here's how it's done, example trivial code fragment: 0100: CALL subr / This jump subroutine... 0102: ... / ...returns here, 0103: ... 0200: CALL subr / and this call... 0202: ... / ...returns here. subr: code here ... RETURN One 8x300 register is set aside for the return linkage mechanism, let's call this RETN. The macroassembler does the work. A local (to the assembler) variable, let's call it R, increments with every CALL macro expansion, arbitrarily from the top of the souce file to the bottom. At the same time, a jump table, call it JUMPS, is constructed where the Rth entry is [pc + 2], that is, the address to return to after the call. (2 instructions are needed to do the CALL.) CALL expands to: xmit R, RETN / store R in register RETN jump subr RETURN expands simply to: XEC RETN, JUMPS / execute JUMPS[RETN] I'm certain I have the syntax wrong, no matter. The jump table called JUMPS looks like: JUMPS: jump 0102 / first call + 2 jump 0202 / second call + 2 ... / etc It would be 'interesting' to cobble up a mechanism capable of recursion, but likely it would be larger than many subroutines. It could certainly be done though, and worse things have been shipped.

19 years, 7 months

11/44 console pinout

by aek＠spies.com

> btw: where did you find that? -- the 44 print set will be up on bitsavers in an hour or so.

19 years, 7 months

Signetics 8x300 instruction set

by aek＠spies.com

here's a scan of the data sheet http://www.bitsavers.org/pdf/signetics/_dataSheets/8X300_1977.pdf

19 years, 7 months

analog computer support information

by dwight.elvey＠amd.com

Hi I'm not sure if I understand your question. You simply change the time constants to be in the range you are looking for. If the original used a 10K and it was 0.1 seconds, using a 100K will make it 1.0 seconds. The capacitance values scale similarly. Do remember to remodel things so that the equation is all integrations and no differentiations. Doing integrators is preferred for these problems. I don't think you change the gains unless you want different responses. You only change the time constants so that you can watch the response. Of course, each step is linear so that you and divide at the input of a stage and the multiply the output if there is a compliance issue. Otherwise, just control the size of your stimulus. Dwight >From: "ahmed abu aqlain" <adomsr(a)yahoo.com> > >I'm Ahmed and I have the following analog computer >Comdyna GP-6 >and I want to implement a high order control transfer function, but I do not know how to rescale of the gain coeffecients fro the high order TFs. > >so, we send you this letter to help us in this point if it possible. > >Thank you very much > AHMED > > >--------------------------------- >Do you Yahoo!? > The all-new My Yahoo! ? What will yours do? >

19 years, 7 months

Mercury computer???

by ken＠seefried.com

> From: "Joe R." <rigdonj(a)cfl.rr.com> > > Anybody know anything about these? The Mercury that I know does high end, custom floating-point semi-super-computers. They are still in business at http://www.mc.com/. Ken

19 years, 7 months

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test-drb December 2004