test-drb June 2009

test-drb@ccmp.vtda.org

233 participants
404 discussions

Diskless Vaxstation 2000 (was Re: PDP-11/23 H786 PSU Fault Finding)

by david_comley＠yahoo.com

--- On Mon, 6/29/09, Sridhar Ayengar <ploopster at gmail.com> wrote: > Is there enough memory in the system to bring up the > network? I'll pull it off the shelf and check what's installed. Memory sounds like a good place to start. -Dave

14 years, 10 months

Diskless Vaxstation 2000 (was Re: PDP-11/23 H786 PSU Fault Finding)

by david_comley＠yahoo.com

--- On Mon, 6/29/09, Sridhar Ayengar <ploopster at gmail.com> wrote: > > I've clusterbooted a Vaxstation 2000 before. Ah - good to know. I'll take another look at it in due course. I'd like to have it up and running. As I recall it would hang while attempting to join the cluster but it's been a couple of years and I don't remember where exactly. -Dave

14 years, 10 months

PDP-11/23 H786 PSU Fault Finding

by david_comley＠yahoo.com

Can anyone offer any guidance on an 11/23 switchmode power supply I'm attempting to repair ? It failed in use and started blowing fuses. I diagnosed a failed bridge rectifier in the primary side and replaced it. That resolved the problem with the fuses blowing. However, when I monitor the +12V line, I can see it peak around +11.5V on power up and then it slowly sags (off-load), all the way down to +4.5V over a period of a few minutes. With a small dummy load connected the 12V line drops down to 4.5V in a matter of less than a second. I can see why it stops at 4.5V; there's a diode, normally reverse biased when the voltages are correct, that's connected between +12 and +5. The +5V line is rock solid at 5.1V. The power supply has a single pair of transistors driving the primary side of T2, and +5 works so I am inclined to think that the problem is somewhere on the secondary side. I pulled the pass transistor (Q3) for the 12V line and checked it with the Huntron Tracker; it appears to be serviceable. The schematic for this is on p75 of http://bitsavers.org/pdf/dec/qbus/MP00740_1123_schem_Oct81.pdf. Is there a common cause for 'sag' in output voltages in switchmode supplies ? I am wondering if this is regulation issue or a problem with drive to the pass transistor ? Thanks, -Dave

14 years, 10 months

Another mystery IC

by ard＠p850ug1.demon.co.uk

I have another mystery IC in a hard disk. This one seems to be made by Analog Devices and is some kind of compaartor/filter. Basically the read signals comes from the HDA (there's a preamp in there I am pretty sure), through a couple of amplifier ICs (MC1350 and TL592) and then goes to this device. Here's what I know about it : -- 14 pin ceramic DIL package -- Analog Devices Logo, HP 1820-5489 house-code -- Inputs (from the amplfier chain) on pins 4 and 13 Inductors between 3 and 2 and 1 and 14 (2 inductors), there may well be other components connected there, some kind of filter +5V on pins 12 and 6 (one may be an enable or something) Ground on pin 5 Does that ring any bells with anyone? -tony

14 years, 10 months

PDP-11/23 H786 PSU Fault Finding

by david_comley＠yahoo.com

--- On Mon, 6/29/09, dwight elvey <dkelvey at hotmail.com> wrote: > Hi > The schematics are not real clear as to what wires > are connected to what wires from board to board. > There seems to be a separate 555 that pulses the T4 that > drives > Q3. On page 80 there is several points you might probe. > You might check the voltages and signals at Q1, E1, Q5, > E2 and Q6. Will do. > The decaying voltage is most likely related to the > start-up +12. > It is only there for a short time to get the regulator > running. Good point - never occurred to me. Does the startup voltage actually get suppressed once the switchmode circuit comes up ? Thanks for the pointers, Dwight. I'll take a look tonight when I get home. -Dave

14 years, 10 months

1541 drive emulators

by gklinger＠gmail.com

Zane H. Healy wrote: > I really like Jim Brain's uIEC, and it's fairly inexpensive. The uIEC is an excellent piece of hardware but it is worth mentioning that it isn't a 1541 "emulator" per se. The only device that can lay claim to that distinction would be the 1541 Ultimate [1]. Unfortunately it's quite a bit more expensive (although it does offer a lot of additional functionality) and doesn't fit in with the OP's requirements. [1] <http://www.1541ultimate.net/> -- Golan Klinger <gklinger at gmail.com> Dark is the suede that mows like a harvest.

14 years, 10 months

Anyone got a 386/486 in the SF area?

by slawmaster＠gmail.com

Lately I've been fiddling around with old Unix versions and I'm finding that things don't work perfectly on QEMU. I'd really like to find a 386 or 486 around the SF bay area to work with... if anybody has a spare lying around, drop me a line. I'd especially like to find one made for running UNIX but that's probably less easy. Also if anyone has a 3B2 that's cluttering up the garage I'd be happy to take that off your hands ;) John -- "I've tried programming Ruby on Rails, following TechCrunch in my RSS reader, and drinking absinthe. It doesn't work. I'm going back to C, Hunter S. Thompson, and cheap whiskey." -- Ted Dziuba

14 years, 10 months

HP32-II repair

by jdr_use＠bluewin.ch

Since we are talking HP calcs : Am i right in believing that an HP-32 II with broken LCD screen is beyond repair ? At the moment I would not even know how to open it.... Jos

14 years, 10 months

FTGH: DEC TS30G (UK)

by robert＠irrelevant.com

Hi All. I'm set to no-mail, due to the volume of mail I was getting from the list, and severe lack of time. Please cc any list-aimed replies to me.. I'm currently clearing out, and have unearthed an old Digital TS30G laptop which up to now I had competely forgotten about. It's of no use to me, but, being DEC, I thought might be of slightly more interest to someone than the normal run of the mill machines.. Any UK collectors about? It's got a PSU with it, and no less than two docking stations. (handy, as they include ethernet interfaces not available on the laptop itself.) I've not tested it, but I seem to recall there was a fault last time it was used,with the screen going completely white. If anybody wants it, it's free to the first sensible reply from somebody who can collect it (Nr Manchester, England) or I might be persuaded to ship it, at cost, if someone is suitably desperate... regards Rob O'Donnell.

14 years, 10 months

Altos Worknet and Altos 486 PSU

by spedraja＠ono.com

Hello. Some questions for everyone which could help me: * I'm searching for one Altos 486 PSU and Hard Disk * Someone worked with Altos Worknet ? * Is this available in some form in the actual simulators as AltairZ80 and so ? Regards Sergio

14 years, 10 months

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test-drb June 2009