I asked my boss if he had a logic analyzer i could beg borrow or buy... his
reply below.
> Do you have a logic probe I can beg borrow or buy?
I have quite a fancy 32-channel 100mhz unit, which I haven't used for many
months. At around $8000 you would probably prefer to borrow rather than buy
it... Mine is a 110v unit, so you'd want to remember to use a transformer...
So, I'm assuming I'm set for a logic probe. !!!!!!!!!!!!!!!!!!!!!!!!!!
WOw. Can it make tea and coffee too? At THAT price it better.
Now for the Multimeter :)
Cheers
A
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Wednesday, February 25, 1998 10:13 AM
Subject: Re: a brain... my kingdom for a brain?
>>
>> Tony's comment, below... about the only equipment needed to repair... was
>> helpful.
>> So, as I have an Altair, a BBC, a KIM, a Sorcerer and various other
beasties
>> awaiting ressurection, and having little (well, OK... no) electronics
>> experience, starting at square 1...
>> a) What should I be looking for in a logic probe. Any recommended models
>> (say, <$100)
>
>I did a lot of repairs using a very cheap Tandy/Radio Shack/Micronta
>logic probe, which was officially a 10MHz unit (although it would do a
>bit more than that). It only cost about $25, I think. Note that there's a
>logic pulser (the equivalent of a signal injector) in the same range
>which is a lot less useful than the probe, so if you go for this one make
>sure you're buying the right unit.
>
>HP make some beautiful logic probes, but alas I've never seen one cheap
>enough to be worth buying. They do turn up at radio rallies, though.
>
>It's 8 times your price range (!), but the HP LogicDart is excellent if
>you are serious about repairs and doing new designs. Probably total
>overkil for repairing micros, though.
>
>As regards specs, all you really need are TTL thresholds (you don't find
>much else in micros - ECL is useful for some minis and workstations, but
>few cheap logic probes have that), and pulse detection down to (say)
>100ns or better. Just about any logic probe will do.
>
>> b) Ditto for multimeter.
>
>Again, you don't need too high a spec - high accuracy is not that useful
>in most digital work.
>
>Analogue or Digital display is fine. I have both - the analogue meter is
>better for looking at
>What you need are :
>
>DC voltage ranges up to about 50V (you only need higher voltages if you
>repair monitors, etc). A sensitivity of 20000 Ohms/volt (== 50uA fsd
>current) for an analogue meter would be fine. Any digital meter would
>have a low enough input current.
>Ohms - especially a good continuity tester. A lot of faults are broken
>wires, defective switches, etc. Make sure the continuity tester responds
>quickly - you want to be able to clip on probe onto (say) a connector
>pin at one end of a cable and run the probe down the pins at the other
>end. If you have to stop for a few seconds on each pin you'll soon go mad.
>
>Again, that's a pretty low spec. AC voltage (up to mains) is useful for
>checking transformers in linear supplies. Current ranges can be handy for
>checking PSU load, etc. But I would estimate that 90%+ of all my
>measurements are either DC voltage or resistance.
>
>If you can afford it, get a Fluke (a 77 or a 79 would be _very_ nice).
>AVO is another good brand. And although I've never used one, there's a
>meter from Tektronix which is probably good.
>
>If those are out of your price range, then just about _any_ digital meter
>costing about $50.00 would be fine. It won't be as robust as the Fluke,
>it won't be as accurate. But it'll be enough for most repairs.
>
>A recomendation. Get a cheap-ish meter like I've just recomended. When
>you get more experience and want something better, get the Fluke. Put the
>cheap one in the car for checking bulbs/battery/fuses/etc when you break
>down.
>
>
>> c) Where can I find a brain? :)
>
>I wish I knew :-). Mine needs upgrading :-)
>
>If you want a book recomendation, try 'The Art of Electronics' by Paul
>Horrowitz and Winfield Hill. There's also a practical book 'The Student
>Manual for the Art of Electronics' by (I think) T. Hayes and P.
>Horrowitz. These books cover everything from resistors to
>microprocessors, and have an intuitive rather than mathematical approach.
>But you won't 'grow out' of them - there's a lot of good sound
>information in there.
>
>> Actually, the Altair will be my first task. I'm thinking of #1 taking
out
>> all the boards. Good idea?
>
>Indeed. Pull the boards and clean all the edge connectors (and just about
>any other metal-metal contact).
>
>-tony
>
>
Typing on a cold machine?!! Now THAT brings back memories.
I remember borrowing a friend's OSI Challenger 1P one winter.
With a metal case, and a fan that sucked air IN to the computer, and forced
it out the keyboard, that was one COLD cold cold way to program!!
A
-----Original Message-----
From: George Rachor <george(a)racsys.rt.rain.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Thursday, February 26, 1998 6:39 AM
Subject: Re: Photo of Smithsonian microcomputer exhibit
>Oh no!.. not down that rat hole....
>80% of the original Matchbox car!
>
>
>
>I shouldn't really type while on cold medicine.
>
>George Rachor
>
>=========================================================
>George L. Rachor george(a)racsys.rt.rain.com
>Beaverton, Oregon http://racsys.rt.rain.com
>
>On Wed, 25 Feb 1998, Tim Shoppa wrote:
>
>> > Maybe replicas should follow the example set by Matchbox (Diecast model
>> > cars). In their case all replicas were made at 80% of original size.
>>
>> A diecast car replica 80% of original size? That's a lot bigger than the
>> ones I used to play with as a kid! And isn't the lack of a motor a
>> dead give-away that it isn't the original?
>>
>> [ :=) for the humor-impaired ]
>>
>> Tim.
>>
>
>
<b) The Intellec MCS8i panel can access not only the 64K address space of
<the 8080 but also the 256 I/O ports. If you flip the right switch you can
<use the top 8 switches to select a port and output data to it using the
<bottom 8 switches. All this is done in hardware (the frontpanel simulates
<an 8080 I/O cycle) without the use of the 8080.
It was a neat hack too!
Allison
In one of our original PC's I found a board labeled "5250 emulator" with a
1 1/2" square chip and a fifteen pin connector on the back.
Can anyone tell me anything about this?
Thanks
Charlie Fox
Re: BBC repair
Oh, forgot to mention
I have this interesting gold thingy. It fell out of the BBC when i opened
it.
To be more precise, it was wedged between a couple of chips, which I guess
were RAm. top right near the video connector. It's about half an inch
long, looks like it wrapped around the end of a wire.
Hollow, one end looks like it can be crimped (its split in half). THe other
end shaped like the mouthpiece of a wooden flute/recorder.
I have an image up.
http://www.comcen.com.au/~adavie/bbc.jpg
What is this and do I really really need it?
A
>QNX is a very small micro-kernel OS that has the look of Windows 95, has
>builtin TCP/IP networking, a notepad, a few other little doodads, and to
>top it off, a fully functional HTML 3.2 compliant web browser. Also
Okay, QNX sounds pretty cool, but I hafta throw my vote in for Arachne.
Graphical DOS web browser runs on anything, I think, and works great. I
found it when I was looking for something to preview my web pages in (I do
'em in a DOS Editor).
--------------------------------------------------------------------- O-
Uncle Roger "There is pleasure pure in being mad
roger(a)sinasohn.com that none but madmen know."
Roger Louis Sinasohn & Associates
San Francisco, California http://www.sinasohn.com/
>Firstly, does Mode 7 behave correctly? Not only does it have the simplest
>mapping, it also uses different address buffers between the 6845 CRTC
>chip and the RAM. On my diagram, IC10 and IC11 are used in Mode7. IC8
>and IC9 are used in all the other modes. So if _all_ modes, including
>Mode7 are faulty, then it's unlikely to be a buffer problem.
Mode 7 behaves as my earlier email. Basic repeat unit 64. Mode 0 behaves
as if we had two mode 7 screens - and the repeat unit and behaviour
unchanged. That would make it unlikely to be a buffer problem, by your
reckoning.
>Secondly, go into mode 0, and count the number of characters until it
>repeats. Multiply that by 8 (to get the the number of bytes before it
>repeats) and that'll tell you which address line to look at.
Well, 64 characters. That would make it.... 256 bytes, no?
Therefore, (guessing) um.... address line 8 (I start counting at 0).
SO... uh.... where?
Sorry I'm such an electronic idiot.
A
Anyone feel the urge to own a TU81 6250BPI tape drive that's in
Milwaukee at the moment? Get in touch with this fellow...
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From: "Dan Reese" <danreese(a)execpc.com>
Newsgroups: comp.sys.dec
Subject: TU81E 9-track tape drive available
Date: Tue, 24 Feb 1998 07:16:02 -0600
Organization: Exec-PC BBS Internet - Milwaukee, WI
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There is a TU81E 6250 BPS 9-track reel-to-reel tape drive available for
the
taking in Milwaukee, WI. Has been out of service for over a year, but was
in good working order when last on-line. A KLESI adapter is also
available
for use in a Vax 4000 system. Connecting cables included, along with
whatever manuals that can be found.
You pick up, but will consider shipping if you absorb shipping costs.
Contact:
Dan Reese
danreese(a)execpc.com
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The Dragon's Cave BBS (Fido 1:343/272)
kyrrin2 {at} wiz<ards> d[o]t n=e=t
"...No matter how hard we may wish otherwise, our science can only describe
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define any of them!..."
