About the fisrst RL02 spin problem:
THere's a small rubber button that pushed the pack cover detector too see if you
have the pack cover in. That button had become depressed over time by pressure.
I fitted a washer around the rubber plug to stick it out more.
Now the drive spins up normally and it doesn't need me to weight the lid.
-------
>
>> > Can I make one,
>> > get one REALLY cheap, or operate the thing without one? Also, it
>>
>> Don't know. I bet it emits RF, and the tablet probably has a circuit
board with
>> traces running horizontally on one side an vertically on the other.
My Dauphin
>> detects the pen in this manner.
>
>The older sumagraphics tables like the Bit Pad 1, the ID series and the
>Apple graphics tablet worked by sending a magnetic pulse along some
wires
>made of special alloy. I believe this pulse travelled at approximately
>the speed of sound in the wires - there was a shock wave that travelled
>along them caused by magnetostriction.
Magnetostriction?
>The puck was a simple sense coil. I had to rewind one of mine once, and
I
>seem to remember it was something like 11 turns of 30swg wire. That
would
>be a start anyway.
>
>Also I seem to remember that the buttons on the puck had 100k resistors
>in series with them. The other side of the button was grounded. This is
>also critical - otherwise noise breaks through into the sense coil
amplifier.
>
> / 100k
>Gnd----/ o---\/\/\---- Button input
>
Do you know the pinout for the plug?
>
>Certainly the Bit Pad 1 came in a serial version (and also a GPIB
>version and a parallel version).
>
>There's another type of tablet that consists of an XY matrix of PCB
>tracks - plain copper PCB tracks. They are individually driven by a set
>of decoder/driver chips which are driven by a simple microcontroller.
>Again the puck is a simple sense coil.
>
>Thing is, it has a much better resolution than the spacing between the
>tracks. And there's no extra hardware, like high-speed-ish counters.
I've
>never figured out how that one works - any clues?
>
Well, I have this second one. My guess is that it uses capacitance,
like touch-to-turn on lamps.
>-tony
>
>
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I have a bunch of 80 MB mac hard drives. would an old PC SCSI card
run them?
>
>HUH? Neither of these are an helped/hindered by the 386. SCSI is not
>needed to run 1.44/1.2 FDDs. You can put scsi in there even when it
was
>an plain xt. To run the bigger floppies you need a controller that
will,
>most XT controllers will not. JDR and JAMCO sell a board that will do
up
>to 2.88 drives in a XT slot.
Has anyone actually seen a 2.88 MB floppy drive?
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Ward Donald Griffiths III wrote:
> Max Eskin wrote:
> >
> > I found a PS/2 Model 70 recently, which would normally have a 386,
> > but the previous owner installed a Cyrix 486 upgrade chip. Does
> > anyone know if I can use a 386 math coprocessor with this? I want
> > to run AutoCAD.
>
> The i486 has a coprocessor built in, I assume that the Cyrix does
> as well. Try the software. IIRC, AutoCAD doesn't _require_ a math
> coprocessor, but one does help performance by an order or two of
> magnitude on a 386.
> --
No, the Cyrix 486DL (I assume it is a DL or DR2 if it's in a 386
motherboard) is not the same as an Intel 486. The Cyrix 486DL was an
upgrade CPU for the 386 pinout, adding a 486 instruction set and 1K
internal cache. The 486DR2 version was clock doubled. These CPUs do
not have floating point. Generally an Intel 80387 did not work
reliably, but the Cyrix 487 co-processor did. ULSI (and I think IIT)
also made 487s. You can try the Intel 387, sometimes they ran ok,
mostly it depended on the speed range used.
Jack Peacock
> Date codes are stamped on just about every IC, and some other parts too.
>
> They are generally a four digit number of the form YYWW, where YY is the
> last two digits of the year in which the chip was munfactured and WW the
> week number, from 01 through 52.
>
> Examples would be "7830" for the 30th week of 1978, and "8101" for the
> first week of January 1981.
>
> Generally for the old machines we talk about on this list, the chip type
> code is easy to differentiate from the date code, because of the
> prevalence of 7400-series TTL chips. Any 74xx or 54xx number will be the
> chip type, while the other number will be the date code.
I learnt this one in a DEC PDP11-05. The chips are TTL - 74xx not
74LSxx or anything else - and almost every date code is in 1974. (i.e.
also 74xx). The trick is that the chip no. usually has manufacturers
name codes, package codes etc. embedded, e.g. SN7400N for one of the TI
packages (I forget which!), while the date code in my experience never
does. Be warned! I read somewhere (Horowitz and Hill?) that many
distributors got this wrong in 1974 and shipped the wrong chips...
Philip.
> At 07:48 PM 4/2/98 -0600, you wrote:
> >* I'll return or destroy any personal data I find on a machine I acquire.
>
> change to:
>
> ...acquire, keeping it in the strictest confidence should I find it
> necessary to view it.
>
> or something like that.
I would also substitute "personal or commercially sensitive data" in
this rule.
Philip.
A while ago, I found a SummaSketch Plus graphics tablet sans the
little mouse thing, whatever the official name is. Can I make one,
get one REALLY cheap, or operate the thing without one? Also, it
hasthree connectors; a serial connector, an RJ-11 connector that
I think is for the mouse, and some kind of weird square four-pin
connector; what is that for? Do I need some kind of card?
NOTE: I do have AutoCAD with the appropriate drivers.
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Hi all,
Well, I've got some good news, and I've got some bad news.
The good news is that I've finally had my IMSAI 8080 sent out to me
>from Connecticut! It's in my "workshop" (a.k.a. the Garage) right now.
The bad news is... my parents, god bless 'em -- They really didn't know
any better, and it's partially my fault for not getting it shipped out
to me sooner -- well, they had the poor thing stored, along with my BYTE
and Dr. Dobbs collection, in an outdoor shed. Although largely protected
>from the elements, this poor sad little IMSAI has endured two New England
summers followed by two New England winters in a non-climate-controlled
room. Great.
The practical upshot of this is that it's not doing so well. I need
help :)
The power supply seems to be worst off of everything. The boards,
although needing to be cleaned of some spots of mildew, seem mostly OK.
Possibly a few tiny rust spots -- I'd say 100% of the chips are replacable
by easily-found parts, either period pieces or newer pieces. But probably
99% of the chips won't need replacing. They seem to be doing very well.
I have two Cromemco ZPU boards, so even if one has some bad parts,
I should be able to take spares from the other.
But that power supply... eek. The transformer is covered in a thick layer
of rust, and the whole thing just looks dirty and mildewed. I think
the best course of action now would be to desolder every component of
the power supply and build a new one -- sadly, losing a bit of IMSAI
authenticity in the process. Oh well... Say, does anyone know where
I can get a pair of 95000uF 15VDC electrolytic capacitors? =) Oh, and
a pair of 10000uF 25VDC -- mustn't forget those.
The good news here is that I have the original IMSAI User Manual --
the one with complete system diagrams and assembly instructions, since
this was a kit. Full parts list and photos from many angles. This will
make rebuilding the power supply _so_ much easier.
The S100 backplane is mildewed as well. How should I clean this? I know
this is probably a FAQ question, but I still can't find the archives of
this list, I'm afraid.
I'll probably also need to replace the little screws that hold on the
front panel plexiglass. It's really odd how some little components,
like these, rusted over terribly, while 95% of the rest of the system
just has mildew or mold spots, and no rust. Weird (but wow I'm glad.
Of course, I think the chassis is aluminum, so it's no wonder it didn't
rust =) Time for a Fry's run...
If anyone would like to help me out with this little project, please
drop me a line. I'm a bit out of my league here -- see, I'm mainly a
software guy, and my hardware building/fixing experience is very slim.
I can work a soldering iron alright, but that's about where my electronics
skill ends :) I have, however, always wanted to learn.
Suggestions welcome! Note, however, that it is not productive to
point at me and go "HA ha!" :)
-Seth
I have a newly acquired DEC VT 131 with keyboard to get rid of. In great
physical shape, untested working condition. I'll know more about the
electrical condition.
Whether working or not I need $15 plus shipping for this unit. I need to
weigh it as well but wanted to give everyone a chance to mull it over
and have a chance to inquire while I check on the working condition and
weight.
--------------------------------------------------------------------
Russ Blakeman
RB Custom Services / Rt. 1 Box 62E / Harned, KY USA 40144
Phone: (502) 756-1749 Data/Fax:(502) 756-6991
Email: rhblake(a)bbtel.com or rhblake(a)bigfoot.com
Website: http://members.tripod.com/~RHBLAKE/
ICQ # 1714857
* Parts/Service/Upgrades and more for MOST Computers*
--------------------------------------------------------------------
One other item I recently acquired that I thought I'd ask about.
Ever hear of the Exatron Stringy Floppy mass storage system? The
one I have was apparently used with a TRS-80 model 1. But it had
a brochure that said it was available for S-100 and 6800 systems.
It is a minature tape system...the tapes look like very small
casette tapes. The tapes/waffers apparently come in different
sizes with a 5 foot length holding about 4k. Anyone ever use one?
Seems pretty interesting.
Thanks...Win
--
Win Heagy
wheagy(a)erols.com
