I doubt that there's need for the high voltage drivers. Any open collector
should work if your LED's are driven from the 5V supply.
Be careful with your socket, i.e. make sure things will fit back together
before you solder it in!
Dick
-----Original Message-----
From: Bill Sudbrink <bill(a)chipware.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Wednesday, June 30, 1999 3:20 PM
Subject: IMSAI front panel (7405 == 7406)??
>I'm suspicious of one of the 7405s (Hex open-collector
>inverters) driving the data lines to the MPU-A. I
>don't have any replacements, but I do have a handfull
>of 7406s (Hex open-collector high-voltage inverters).
>The pinouts in the Chip Directory look the same, only
>difference by them is that the 7406 is "Maximum output
>voltage is 30V". I think I'll try socketing the
>suspect chip (U1 for anybody keeping score) and putting
>in a 7406.
>
The 7109 is an adc, of the dual-slope integrating variety more or less like
the panel meter IC's Intersil developed and everyone else copied. I think
www.maxim-ic.com is the place to look for the functions on this board. I'll
let you guess what the DAC800 is. (chuckle) If it's working, it's probably
a keeper. Look for any additional identifiers and then hit the web with a
search for that.
Dick
-----Original Message-----
From: Joe <rigdonj(a)intellistar.net>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Monday, June 07, 1999 8:38 PM
Subject: ID this PC card
>Hi,
>
> I picked up an old IBM AT the other day and found a strange card in it.
>It's a full length card with an 8 bit ISA plug. It has two Burr Brown
>DAC800P-CBI-V ( D to A?) ICs on it along with a large IC marked TSC
>7109CPL. (I have no idea what that one is.) There is also a small flat
>sealed Yuasa NiCad battery in the top corner of the card. It has 37 pin
>male connector on the back and it's marked "copyright 1983 MBC". Most of
>the ICs are dated 1986. It looks like it may be some kind of D to A
>convertor card. Does anyone know what it is for sure?
>
> Joe
>
>
>
A couple of people mentioned the SS50 bus, but they should
have also mentioned the SS30 bus because they go together.
Other well known micro buses not mentioned would include
the TRS-80 Model 1 expansion bus and the 50 pin Sorcerer
S-100 expansion bus.
Some of these micro buses also have different versions. The
S-100 bus was used (and IMHO abused :) for about 7 years before
it was locked down to a standard. There is an extended Benton
Harbor Bus which is easily identified as a double row of pins,
instead a single row of pins.
--Doug
====================================================
Doug Coward dcoward(a)pressstart.com (work)
Sr. Software Eng. mranalog(a)home.com (home)
Press Start Inc. http://www.pressstart.com
Sunnyvale,CA
Curator
Analog Computer Museum and History Center
http://www.best.com/~dcoward/analog
====================================================
Hi Scott:
In a message dated 6/30/99 7:04:18 PM Eastern Daylight Time,
scott(a)saskatoon.com writes:
> > Other than the Timex/Sinclairs, what's the cheapest machine which was
> > available in 1982 that I could have used to learn BASIC and assembler
and
> > machine code -- at home?
>
> VIC-20. I bought mine for $600CDN in either 1981 or 1982 (not sure)
My point exactly -- in '82 $100 US was no sweat, but $500 US was more than I
could afford. So, my choice, again, was crap computer or no computer.
> I hope this doesn't really sway the argument either way. I'm really
> neutral on the subject. Some people collect PDP-8s, some people collect
> what's 'popular', as for me, I'm still looking for a VIC-1540 because I
> could never afford one back in the early 80s.
And some of us are sentimental old fools who just collect for purely sappy
reasons. In Feb '99, I hadn't seen or thought about a Timex/Sinclair for 13
years. One day I found the manual while cleaning out a closet (computer long
since lost or given away). I did a web search and was _floored_ to find an
intensely active international user community still supporting these critters.
This led me to another discovery: development of the ZX81 platform
continues. Examples are: bumping the tape transfer rate from native 300 bps
to 4800 bps _using_software_. Efficient BASIC and FORTH compilers. Hi-res
graphics utilizing non-volatile memory (the ZX81 inventor, Sir Clive
Sinclair, repeatedly stated that this was impossible). IDE hard drive and
floppy drive i/fs. RAM expansion to 1 MB. I.e., developments by users which
go completely beyond what was originally imagined by the makers of the ZX81.
Sincere question: is this also the case with the larger machines which are
being collected/restored? Has anyone figured out how to connect (for
example) a Snappy to a PERQ? No disrespect intended, as I have nothing but
admiration for folks who take the huge amount of time & trouble to revive a
PDP-8 or 370, but it appears to me (and I'm new here, so don't clobber me too
badly) that "big" classic computer collectors take pride in returning a
machine to its original condition, whereas the ZX81 crowd is by and large
more interested in "how can I make this thing act more like a 'real'
computer."
Anyway, when I began to collect them, I had no idea they were "popular."
> Also, back to the question above, I think by 1982 we might also have had
> the Atari400. The C64 must have been around this time too. Probably the
> Coco as well. Really, 1982 is pretty close to the start of the 8bit
> explosion.
CoCo I'm not sure of (without checking), 400 & C64 yes. But, all of these
sold for many times the cost of a ZX81. Additionally, none of the above have
that perfect wedge shape, which really does make a perfect door-stop. ;>)
Regards & thanks for your input,
Glen Goodwin
A Fledgling Collector
0/0
I am risking the effects of that famous quote, "Better to be thought a
fool..."
I have a 15V DC powersupply that has no other rating on its sticker than
180 watts. Now, with my [extremely] limited knowledge, I did the simple
math and worked out that I could safely pull 12 amps out of this
PS...am I right? Does it really work this way?
Aaron
The phrase "prices...out of reach of people who can handle these machines"
sounds like you don't consider anyone with money to be technically
competent. I'm sure that's not what you meant... right?
Kai
-----Original Message-----
From: Max Eskin [mailto:max82@surfree.com]
Sent: Wednesday, June 30, 1999 3:10 PM
To: Discussion re-collecting of classic computers
Subject: Re: State of the Hobby
I agree that this is not a legitimate thing over which to become angry,
but there is an issue that this is driving the prices up, out of reach of
people who can handle these machines, and into the reach of people who
want to encase them in plastic and put them into their 500 sq.ft. living
room. This is causing some hostility.
--Max Eskin (max82(a)surfree.com)
http://scivault.hypermart.net: Ignorance is Impotence - Knowledge is Power
In a message dated 6/29/99 6:14:14 PM Eastern Daylight Time, Tony Duell
writes:
> This means the history of computing is being distorted. Truely important
> machines are being forgotten. Other machines, much less significant, are
> being remembered. This is not a good thing.
>
> OK, let me ask a very simple question. I will give below the
> specification of 2 machines, both from around 1980. The questions are :
> Which do you think is the more historically important, and which one
> would fetch a higher price (Oh, and would anyone care to name the 2
> machines :-))
>
> OK. Machine A :
>
> Processor : Custom 16/20 bit CPU. Graphics processor. Z80-A for I/O
>
> RAM : 1Mbyte
>
> Storage : 8" floppy disk, 24Mbyte hard disk
>
> Keyboard : Full QWERTY keyboard, Keytronics
>
> Display : Bitmapped display, 768*1024 pixels (portrait monitor)
>
> Mouse : Sumagraphics Bit Pad 1
>
> Languages : Pascal, LISP, etc
>
> Comments : Version of the first commercially-sold graphics workstation
>
>
> Machine B :
>
> Processor : Z80A
>
> RAM : 1Kbyte
>
> Storage : Sockets to connect optional audio cassette recorder
>
> Keyboard : QWERTY membrane keyboaard
>
> Display : Text (22*23 or something like that), block graphics. Disappears
> when program running
>
> Mouse : You must be joking
>
> Languages : 4K ROM containing strange (integer only?) BASIC.
>
> Comments : Very inexpensive home computer
Machine B is very obviously a Sinclair ZX80 or ZX81. Pardon my confusion,
but are you saying that the ZX80/81 was "much less significant?" Perhaps I
misunderstand.
Millions of people worldwide were introduced to computers by these machines
(and their Timex cousins). Because of the low price, people bought them to
see if they "liked computing" -- if not, they could throw them away and only
be out $100 or so.
On the other hand, many, like myself, found they had a small talent for
working with computers -- in whatever capacity -- and thus found employment,
careers, and satisfaction because of their initial experience with
Timex/Sinclair computers.
> I think that if you own a classic computer you should learn how it works,
> how to use it, how to repair it, etc. Note, I am _NOT_ saying that you
> have to be qualified (after all, I'm not). I am not saying that you have
> to know everything before you start. I am saying, though, that you should
> want to learn.
The TS computers' simple but clever architecture encouraged learning all the
"how to's" you mention above.
But, perhaps I misunderstood what you were saying . . .
So: what are these two computers? Which is the most historically important,
and, in your opinion, which would fetch a higher price?
BTW, I use my Timex/Sinclair computers for some purpose at least five days
out of seven.
Regards,
Glen Goodwin
0/0
Hi Tony:
In a message dated 6/30/99 10:34:53 PM Eastern Daylight Time,
ard(a)p850ug1.demon.co.uk writes:
> There's little point in working out how to link
> a modern laser printer to a PERQ when you can get the original Canon
> interface card and hook up a CX-VDO.
Good point -- why reinvent the wheel?
The thrill for many ZX81ers is sticking wings on an oxcart and watching it
fly (erratically, and for a short time . . .)
> And other peripherals do get designed. Like a chording keyboard, a way to
> boot PERQ microcode from a PC (I _must_ find time to finish that!), etc
>
> Trivial hacks, like replacing 8" drives with 5.25"(1.2M) or 3.5" (1.44M)
> drives are common.
Great! IMHO, advancement of a platform is as important as preservation of
that platform.
> \begin{tongue-in-cheek}
> Of course if you start out with a real computer...
> \end{tongue-in-cheek}
Yeah, I know, but it was my first computer, and I still love the damn thing.
If it weren't for my exposure to the ZX81 (having no college education) I'd
probably be managing a burger stand somewhere, instead of maintaining my
lofty position as a _highly_paid_computer_professional_ and
_independant_small_business_owner_.
Thanks for all of your help,
Glen Goodwin
0/0
This is an adac corp. model 1664ATTL double-wide
board. I have no idea what buss this is for,
but I think it is some kind of data aquisition
thingie.
Have no idea if it works; anybody want it?
$3 plus postage.
Jeff
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