test-drb December 1998

test-drb@ccmp.vtda.org

168 participants
844 discussions

by bill＠chipware.com

> If it has a C1 next to it you can bet it is a capacitor. > You should have rows of them on the card. Nope, I'm sure that it was a diode. The ends of it were still on the leads. There is another one next to where it was labeled "C25". > Is it is the one by the resistor and transistor? > Or the one by the two 'normal' looking capacitors on the other side? There are no transistors on the board. The diode is in the corner, near the power connector. Just for reference, the main component on the board is a 40 pin IC labeled: AMI KOREA SHUGART 16271-0 8130B1M There are only three caps that I see on the board. They are the little silver can types, no ceramics. They are labeled "C17", "C22" and "C26".

25 years, 11 months

Virus Checking

by SUPRDAVE＠aol.com

In a message dated 12/31/98 0:33:13 AM EST, Pjoules1(a)cs.com writes: << Agreed, apart from home produced or piarate ones which you have already pointed out are always suspect. IIRC there have been rare ocasions where floppies have been distributed with viruses in bulk, one was a batch of preformatted ones where the master (or duplicating machine or whatever) was infected with aa boot sector vvirus, and I belive that there has been at least on occasion where a major software house accidentally distributed some but that was many years ago. >> i think not long ago that a commercial mac cd was shipped with a virus. can anyone elaborate?

25 years, 11 months

8 inch floppy notes

by bill＠chipware.com

Using the CP/M FAQ I built a 34 to 50 pin converter. A couple of notes: 1) read the whole FAQ. The wiring instructions in Q14 don't take into account the IBM-PC "floppy twist". Q16 gives the wiring that worked for me. Spent an hour scratching my head on that before I read further. Primary indicative behavior: seeks with no head load, software reporting access attempts with no head load. 2) The Radio Shack General Purpose Component PC Board (Cat. No. 276-168B) makes a great platform to build the converter on. Took me about an hour to solder it up. 3) There seems to be a bug in 22DISK versions greater than 1.31. The directory read code does not seem to use the seek delay. Either that or it simply misses a head step. It always reports cylinder 2 read errors. Despite this, it can format, read and write just fine. It just can't display directories. Spent another two hours on that. BTW older versions of 22DISK can be found with FTP searches, sorry I don't remember where I got 1.31 (I downloaded 5 different versions from different sites). Bill Sudbrink

25 years, 11 months

Replies to old threads

by Philip.Belben＠PowerTech.co.uk

Hi! I'm back! I've just been off the list for a few weeks - first a course, then two weeks ill - and I came into work after Christmas to find 1200 messages waiting for me from Classiccmp. I am trying to put replies to a few older threads together in this message. SYSTEM/23 I too have a Datamaster, and a number of the manuals. I think these machines ought to be kept running, so I'll provide what help I can. The service manuals are mainly board swappers' guides, but there is some useful info there if you dig hard enough... SINGLE INSTANCE MACHINES Do I have the only Tek 4052? I think there are at least three 4051s on the list. I also have an IBM 6150 but I doubt that's unique. I don't have the only FTS Series 88 on the list - I distinctly remember giving Tony Duell one for his 21st birthday - but I'd guess I have the only FTS Series 86. Oh yes. Tony's P850. Tony wrote: > Mine was made in about 1971. Last time I powered it up was about 3 months > ago, and it behaved perfectly. I've had it for about 12 years, and in > that time it's needed the switch contacts on some of the frontpanel > switches cleaning, and one new TTL chip in the processor. In other words > it's pretty reliable. And you had to re-solder some inter-board connecting wires on the core memory modules. IIRC these wires were little strips of springy stuff. Boards wired together with these while lying next to each other, and then folded over, the springy connecting wire acting as a hinge. Unfortunately springy wire doesn't take as well to soldering as ordinary wire... Philip.

25 years, 11 months

Looking for PolaPulse or equivalent

by mbg＠world.std.com

I recently unearthed an acquisition from several years ago (and added it to my home_systems web page). I have a TC200, a handheld, battery-powered portable terminal which appears to have been built by IXO, Inc, yet it has a Digital logo on it (so it either was, or was going to be, marketed by Digital). It is powered by a 6v Litium battery, like the kind you find in a Polaroid film pack (but they are not identical -- the battery terminals are in different places). It is called a PolaPulse battery. Does anyone know of a source for this battery nowadays? Also, does anyone happen to have any documentation or other information about this thing? Thanks in advance... Megan Gentry Former RT-11 Developer +--------------------------------+-------------------------------------+ | Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com | | Unix Support Engineering Group | (home): mbg!world.std.com | | Compaq Computer Corporation | addresses need '@' in place of '!' | | 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ | | Nashua, NH 03062 | "pdp-11 programmer - some assembler | | (603) 884 1055 | required." - mbg | +--------------------------------+-------------------------------------+

25 years, 11 months

Transformer theory (was:Re: Another ~1960 computer kit)

by Philip.Belben＠pgen.com

Dave Dameron wrote: > OFF topic: > Max wrote: > There's little need to make coils these days, and wiring electric lights > isn't very fun when one can play around with things millions of times more > complex. > > Hey! I've wound several experimental coils this year. Did you wonder _how_ a > transformer works? I know the equations to design one, but am asking > something more fundamental. The secondary winding of a transformer has > voltage induced in it, but what couples the energy to it from the primary > winding's magnetic field? > (Hint: The magnetic field can be zero at the secondary) As the list's resident electrical (as opposed to electronic) engineer, I feel I must make a stab at answering this. Especially since my first job at PowerGen was research on transformers. (Not at this fundamental level though - I was looking at fault detection systems) As I see it, when you have a winding linked with a magnetic field, you induce a voltage in the winding proportional to the rate of change of the field. If you like to visualise lines of magnetic flux, the voltage is related to the number of flux lines that actually cut the wires of the winding, not the flux linked with the winding at any time. This means, among other things, that (for sinusoidal ac) the flux is zero when the voltage is at its peak and vice versa. The transformer, though, is not a differentiator since the magnetic field is proportional to the integral of voltage in the primary. That is, flux = integral (Volts in).dt; (Volts out) = d(flux)/dt (assume = means "is proportional to") Note also that the flux depends only on voltage, NOT CURRENT. You associate magnetic fields with currents (well, I do, anyway), and as you increase the primary current you expect the field to increase. But it doesn't. An equal and opposite effect from the secondary current exactly balances this. This has a number of implications that are quite important for my current (pun not intended) job, modelling power systems. 1. The equivalent circuit of a transformer has a branch in parallel with the primary, the magnetising branch. This is an inductance representing the magnetic field (and it's in parallel, so it depends only on voltage as above) and a resistance representing "iron losses" 2. No transformer is perfect. There is regulation - inductance and resistance apparently in series with it. The resistance represents "copper loss" - the physical resistance of the windings. The inductance represents flux in each winding that _does not_ link with the other, and therefore is not backed off by current in the other winding. But in an electrical system model, the simplest representation of a tranformer is a series inductance connecting two sides of the transformer. Ironically, this represents physically the magnetic field that does not connect the two sides of the transformer! 3. For metering, protection and the rest, you see a lot of current transformers. One of these consists of a high current, low voltage primary - usually a bar running through the middle of the toroidal core - and one or more multi-turn (low current) secondaries. The equation is simple. The mmf (magnetomotive force = amps * turns) of all the windings add up to zero (equal and opposite effect of secondary current again). Because the measuring kit acts as an effective short circuit on the secondary - or drops a few volts at most - the magnetising current is almost zero, and you can thus make very accurate measurememnts. Is this the answer you wanted? Final note. What do you mean by "the primary winding's magnetic field" as distinct from that of the secondary? To a good approximation, the magnetic field is the same at both the primary and the secondary. It may be close to zero, for reasons I described. But the difference between the mag. field at the two windings contributes only to the equivalent series impedance. It is not something to look at when discussing the detailed operation of the tranformer. > As for wiring lights, Christmas tree light strings here are now cheap series > strings although the bulbs may have some wire turns wrapped around the leads > to prevent a open circuit if a bulb burns out. This often don't work, so the > entire string is usually thrown away, like many modern ASIC type computer boards Aargh! I've not heard of that (throwing the whole string away) before but I can well believe it. Philip.

25 years, 11 months

OT, but info needed: RAM uprade

by allisonp＠world.std.com

<> Yes. The 8259 PIC (interrupt controller) is fully programmable for edge <> and level. It's possibel to go from edge to level on a common PC but you < < <Unfortunately the interrupt inputs on the 8259 are always active high <(specified clearly in the data sheet), so you still need inverters on all <the inputs for active-low lines. Yes and they would be needed as putting raw unbuffered mos inputs on a bus is bad form. <all, the reason for having a PC is compatibility. There are plenty of <nicer machines to hack about with (which is where we started). yes, multibus and other implmentations were better. Even S100 got that part right! Allison

25 years, 11 months

Looking for PolaPulse or equivalent

by mbg＠world.std.com

I know, but the ones in the film packs aren't compatible with this one. I'm going to try to contact polaroid about it... Megan D

25 years, 11 months

Osborne 01 for only $5000.00

by roblwill＠usaor.net

I wonder if it was a mistyped $50.00.... -- -Jason Willgruber (roblwill(a)usaor.net) ICQ#: 1730318 <http://members.tripod.com/general_1> -----Original Message----- From: Phil Clayton <musicman38(a)mindspring.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, December 31, 1998 3:11 PM Subject: Osborne 01 for only $5000.00 >Gads!! Check this out on eBay !!! Ha! Ha! HeHeHe!!! > >An Osborne 01 for an opening bid of only $5000.00 HeHeHe!!! >As stated in the ad it could be a "Corner Stone" of your computer >collection.. > >He is even generous enough to include free shipping.. HeHe!! > >http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=50980862 > >Funny thing there are no bids on it yet.. <Grin> > >Phil.. > > >

25 years, 11 months

ZDTV sightings...

by roblwill＠usaor.net

I've got a Tandy 600. When I try to boot it, it gives an error message, seeks the floppy, then shuts off. When I restart it, it says "critical system error", or something like that, and goes into ROM (MS-WORKS). Then when I try to access something, it locks. -- -Jason Willgruber (roblwill(a)usaor.net) ICQ#: 1730318 <http://members.tripod.com/general_1> -----Original Message----- From: Roger Merchberger <zmerch(a)30below.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, December 31, 1998 1:37 PM Subject: ZDTV sightings... >ZDTV is running a news story on donation of old equipment (right now) and - >of all things - they had a *big* table full of classic equipment! Just in >glancing, I saw 2 Tandy 100/102's, I think an Epson HX-20, and - >wherethehell'dtheygetit??? a Tandy 600! That really caught my eye. > >I'd like to find out what they are doing with the machines *after* the >story... > >See ya next year, >Roger "Merch" Merchberger > >

25 years, 11 months

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test-drb December 1998