test-drb May 2004

test-drb@ccmp.vtda.org

244 participants
500 discussions

by pete＠dunnington.u-net.com

On May 31, 7:49, Jos Dreesen wrote: > > Pete Turnbull heeft op maandag, 31 mei 2004 om 00:03 (Europe/Zurich) > het volgende geschreven: > > > > I've got an Exar databook, but I'm afraid it's dated 1992, and > > > > Could your 22-908-03 be something to do with a hard drive controller? > > It was part of keyboard matrix. Tony's suggestion seems to be spot on. > Exar seems to have had a very broad range of devices back then... Yes, I'd forgotten about those keyboard chips. -- Pete Peter Turnbull Network Manager University of York

21 years

Switching supply expertise?

by dave04a＠dunfield.com

At 21:04 30/05/2004 +0100, you wrote: >> >> SMPS are always a pain to troubleshoot, and I've always opted to find a >> replacement. In this case that isn't probably feasible so --- > >They are a pain to troubleshoot, but they're also a part of the classic >computer, and thus should be repaired and preserved. Why do people seem >to think that 'classic computer' == 'CPU only'? Agreed - I could easily put in a PC supply, and I even have a couple from "slimline" PC's which would probably fit the box - however I want the machine to be as original as possible. >> I'd buckshot the components in the switch driver, such as the IC. Sounds > >In a supply of this age, I would not be suprised if the chopper driver >was discrete transsitors. It is - the only IC is the Opto-isolator. Anyway - I found the problem - It was a shorted capacitor on the primary side of the transformer - what threw me off was it was NOT one of the electrolytics... There's another one beside it which is just like it, so I think I will replace both. Supply works fine now - and so does the entire machine. (Joy at getting an old Apple clone working somewhat overshadowed by the fact that I finally found a Kaypro today!) Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Vintage computing equipment collector. http://www.parse.com/~ddunfield/museum/index.html

21 years

Exar 22-908-03 anyone ?

by pete＠dunnington.u-net.com

On May 30, 22:25, Jos Dreesen wrote: > My Lilith workstation keyboard seems to have taken an "electric" > beating, i.e. a 12 v to 5V short. > The wiring inside the machine was not the best...... > > It took out the 8035, a 74ls373 and, much worse, an unknown to me Exar > IC 22-908-03, datecode 1983 > > The first two are easy to replace, the Exar is much worse. > > Anybody have a pinout, a datasheet or an idea just what it might be ? I've got an Exar databook, but I'm afraid it's dated 1992, and everything in it is XR-xxx or XR-xxxx (occasionally with a single letter in front of the xxx). The XR-22xx devices are all phase-lock loops or VCOs, the XR-9080 is a "frequency synthesiser, data synchronizer/1,7 RLL ENDEC" in a 52-pin QFP package. Other XR-90xx devices seem to all be related to disk heads; they're preamps, filters, samplers, and pulse detectors. The XR-9050 seems to be an older simpler version of that. It's a 28-pin SOIC or PLCC described as a "24 Mbit/sec Data synchronization/1,7 RLL ENDEC", "faster than similar bipolar devices". Could your 22-908-03 be something to do with a hard drive controller? -- Pete Peter Turnbull Network Manager University of York

21 years

DECnet/E Version mystery

by healyzh＠aracnet.com

Does anyone know what the story is with DECnet/E V4.2 which apparently dates back to late 1988 or early 1989? How does one go about getting a copy? I'm curious as it's apparently the correct version starting with RSTS/E V9.7 & V10.0, and yet Mentec only lists DECnet/E V4.1 as available. Zane -- -- | Zane H. Healy | UNIX Systems Administrator | | healyzh(a)aracnet.com (primary) | OpenVMS Enthusiast | | | Classic Computer Collector | +----------------------------------+----------------------------+ | Empire of the Petal Throne and Traveller Role Playing, | | PDP-10 Emulation and Zane's Computer Museum. | | http://www.aracnet.com/~healyzh/ |

21 years

IS32 Optic RAM Datasheet and Steve Ciarcia's Micro D-CAM Artical

by dave04a＠dunfield.com

>> I've just checked my archives, and I have a copy of the original >> two-part artical, called: Build the Micro D-Cam Solid-State Video Camera >> I also have a copy of the Micron Technology IS32 OpticRAM data sheet. >> If anyone is interested, I can scan them and post them for public consumption. >Wow - if they're not too difficult to scan, that'd be great. TTBOMK not even >Partminer has a datasheet for the IS32. The BYTE articles are pretty elusive >too, IME. Ok - I will try to do it soon - I know I'm going to be swamped this week, and the material is going to take a little bit of tweaking to scan - they are photocopies, which are fairly readable, but an many of the artical pages the text goes right to the edge of the page (doesn't look like any of it was lost) - so I'll probably have to do it on the flatbed and fool with the page position a bit. Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Vintage computing equipment collector. http://www.parse.com/~ddunfield/museum/index.html

21 years

Pressed Particle Board Shelving Warning

by pete＠dunnington.u-net.com

On May 30, 20:11, Geoffrey Thomas wrote: > It's a tool, a lot like the ones that carpet fitters use to stretch a fitted > carpet, that has two sets of spikes protruding from the base. You grip the > carpet by hitting the tile at an angle with the tool . Surprisingly > effective. There is also a lever in the handle to put more tension in the > grip of the spikes. Haven't seen it in use for a while as there aren't any > carpet tiles with us. ( We're not posh enough , obviously.) Nah, you're just not daft enough to have dust-encouraging carpet in your machine room :-) Besides, it's much easier to get the solder splashes off a hard floor covering, and it doesn't singe when the sparks hit it ;-) I've just been reminded of a photograph I was shown a few weeks ago at a network conference. A senior manager from JANET ops (who run the national backbone) described a recent installation at a site housing one of the main backbone routers. There had been "an issue" with water leakage from the flat roof so the local staff had built protection for the backbone router and its associated equipment (several racks), right in the otherwise-normal looking machine room. It consisted of a greenhouse frame with pitched roof, complete with gutters and downpipes. -- Pete Peter Turnbull Network Manager University of York

21 years

Discharging CRT anode and capacitors on a VT52 DECscope

by dwight.elvey＠amd.com

>From: "Tom Jennings" <tomj(a)wps.com> > >> On Wed, May 26, 2004 at 11:27:51PM +0000, jpero(a)sympatico.ca wrote: > >> > At science museum once saw a very tickish student girl walk off lexan >> > platform by the big sphere HV generator depsite tech's warnings as >> > she stepped off a looong 2 feet long arc... That 2 feet long HV arc must be really packing >> > of power. > >Merely in the interests of spawning another near-infinite regress on >electron fundamentals... > >NO, it specifically had VERY LITTLE POWER, though a lotta voltage. > > P = E * I > >E= voltage, I= Current > > >Probably as much POWER as a nine-volt battery or two. If it had much >more, it would have been an unsafe display, as it's S.K.O.P. (*) to >either not see, or ignore, or spite, safety warnings, and kid science >museums certainly know that! > Hi There is quite enough energy in a normal 9 volt battery to kill a person. It might need a little conversion but the total amount of energy stored there is quite large. I would suspect that there is several times less energy in the large arc as in a 9 volt battery. The fact is, it is the current that kills. The voltage is only needed to induce the current. Once one has enough current across the heart, it makes little difference what the voltage source was, so long as the current is sustained long enough to do damage. Sure, you might also say that it is the total energy that the heart takes in a given period of time. Still, the voltage is relatively constant across the heart for any given current. One might say there are two stages. One where the current holds the heart long enough to kill and the other where the total energy/time is large enough to damage tissue. Still, dead is dead. As far as discharging CRT, the charge can come back after some time. There are surface charges in the glass that will tend to rebuild the charge after a simple discharge. Don't trust a CRT unless a clip is connected from the second anode to the conductive layer on the back. It ain't gonna kill you >from the shock but you might find a lot of glass where you don't want it. Dwight

21 years

Switching supply expertise?

by dave04a＠dunfield.com

Hi, Rescued an Apple clone from the trash yesterday (Ci Base48) - appears to be all there, but power supply is dead. I've had a bit of experience with small DC transformerless switchers, but not with mains power, transformer based switchers like this. Fuse was blown - replace, powered up through a 60w light bulb, the lamp comes on (and stays on) at full intensity - clearly excessive draw. Board bears the name "Seasonic". I have no schematics. >From what I can tell: - Mains power goes to full-wave bridge rectifier and filter caps to produce HV DC supply. - HV DC supply goes through fuse to a single heat-sinked power transistor (C2979) which drives the transformer primary. - Secondaries from transformer are recitied by big heat-sinked diodes, then filtered, and monitored by a circuit, which feeds back through an opto- isolator to the control circuit for the power transistor driving the primary (presumably this is the method of voltage regulation). Opservations: (Powering unit through isolation transformar, variac and 60w light bulb) - With fuse removed, HV DC supply apears to work fine. Filter caps charge up to in the high 100's Volts. - No light from lamp indicating very little drain (as expected). - With fuse installed, lamp lights at full intensity. No voltage measured across HV filter caps at all. - Power transistor does not appear shorted - Removed from circuit and using a diode test function, it shows two normal semiconductor junctions. Can anyone offer suggestions on where to look next? Are there any common failure modes of this type of power supply design? Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Vintage computing equipment collector. http://www.parse.com/~ddunfield/museum/index.html

21 years

Pressed Particle Board Shelving Warning

by pete＠dunnington.u-net.com

On May 27, 18:18, der Mouse wrote: > >> So I'd say that you should never use particle board to carry loads. > > Manufacturers of computer room raised floors will disagree with that > > -- all the high-load ones I've ever coma across are made of particle > > board (usually with a very thin metal cladding, which is to protect > > against moisture and impacts, and to provide electrical continuity). > > Of course, these are 35mm-45mm thick, not 15mm-18mm. > > They also are supported around the whole edge of a two-foot-square > square. Eh? They're supported at the corners only. Some do have metal cladding round the edges, but it's not very strong. > If those shelves were supported every two feet - especially if > they used that kind of thickness - I bet they'd still be just fine. > > >From an engineering perspective, I'd say that particleboard is fine for > carrying loads in the right circumstances, but it is incumbent upon the > designer to know what those circumstances are and design accordingly. Agreed. -- Pete Peter Turnbull Network Manager University of York

21 years

ftp vs http vs scp

by pete＠dunnington.u-net.com

On May 28, 13:34, Roger Merchberger wrote: > Rumor has it that Jules Richardson may have mentioned these words: > >On Fri, 2004-05-28 at 16:48, Patrick Finnegan wrote: > > > Personally, I rather be > > > able to press <UP> than retype a 40+ character command line that I > > > mis-typed a single letter on. > > >Doesn't that particular form of simple command line editing (eg. ^a^b) > >work in the original sh? :-) > > Yes, but <UP><DOWN> and tab file/command completion don't. No, none of those exist in the original 'sh' (Bourne Shell), not even in fairly recent varieties, such as in late-90s IRIX. However, command line editing (using a large subset of vi commands) and command history exist in the Korn Shell (ksh). You might have been confused by that, since many recent UNIXes provide an "sh" as a symlink to "ksh", just as linux provides "sh" as just a symlink to "bash". -- Pete Peter Turnbull Network Manager University of York

21 years

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test-drb May 2004