On 29 Apr 2012 at 18:46, Richard Smith wrote:
> This thread reminds me of a computer we built at school from discrete
> transistors. Each transistor was a NOR gate with three resistors on
> the base and a collector resistor. All soldered onto squares of tag
> board. We put a bunch of them together to build a shift register with
> small laps as output. That would be about 1969 or 1970. Does anyone
> remember any more? It must have been a published design somewhere.
In the late 60's and 70's, radio shack sold some little one-bit-flip-flop boards with lamps. Each flip flop was a little square of circuit board.
There may have been other logic functions available one-to-a-board. I'm pretty sure they were discrete transistors for the most part (even the round package SSI Motorola RTL typically had two gates or flip flops per package.)
You could buy multiples and configure them as a counter, and I'm pretty sure they could be wired as a shift register too.
May have been "Archerkit" brand name. Or "Pbox" brand name although what I remember were not Pbox's but circuit boards.
I tried using websearches to find pictures or docs, but the Googles, they do nothing!
At 07:16 AM 4/30/2012, Bill Sudbrink wrote:
> If you decide to use the "USB power" be sure whatever USB port on your
> computer can handle it. I had mine plugged into one of the "back"
> ports on my computer and it worked fine.
Has anyone made a device that provides a simple indication of the power
supplied by a USB port? Or is there a standard for indicating how much
a device needs to get from the port? This is obviously a source of
> From:?Jon Elson <elson at pico-systems.com>
> Date:?Sat, 28 Apr 2012 18:20:30 -0500
> Subject:?discrete transistor computer
> A while ago somebody mentioned thinking about building a
> discrete transistor computer. ?I ran across the link again of
> the one I saw (only online)
> With all SMT, he packs the boards very closely, performance
> is of course not so great with discrete junction transistors running
> in saturation.
The Rhode Island Computer Museum has four discrete transistor computers.
A PDP-9 and three PDP-8/S systems.
The RCS/RI crew in Providence has a PB-250.
> Why not the SD card? Cheaper, smaller and easy to interface! :)
My gut feeling is that compact flash will live a little longer in terms of being able to get interface hardware a decade into the future. But I could be wrong and SD might have more legs (certainly fewer contacts). And as you point out the serial interface to a SD card is very straightforward so I think you have a good point!
I have had this machine for a while now and decided today to at least start
cleaning it up. It is very dirty inside. The trouble is I can't see how to
get at the motherboard, which I can needs cleaning; it seems to be under a
riveted plate and I can't see any way to get it at it, or even just to
remove the cover for the option cards. Is there a trick to this that I am
missing? I have looked around for manuals, but there don't seem to be any
online. I am also unsure how to remove the option cards, do I just turn the
plastic knob clockwise? It is stiff and I don't want to apply too much force
and break something.
I also just noticed that it is missing the power switch, don't suppose
anyone has one going spare? It looks like probably any DEC rocker switch
would be OK. You can see the type I mean by looking at this
Incidentally, I opened up the PSU to clean that out. It looks pretty bad:
there are quite a few patch wires there, extra components clearly added
after it was built, components that look poorly placed, two resistors
soldered together in series by their leads, an inductor soldered with large
blobs of solder that look worse than anything even I could do. I am left
wondering if this typical of these PSUs or if I have just got something that
has been hacked about.
According to http://so-much-stuff.com/pdp8/repair/subst.php a D672 crosses
to a 1N3656 diode, which you can (theoretically) get from amazon.com (or
your local flavor thereof)
I would resist the urge to plug something that looks similiar in to see
what happens. You run the risk of damaging something else.
On Sun, 29 Apr 2012, RobJ wrote:
> The saga of my broken PDP11/24 PSU (H7140) continues. I have now found a
> shorted diode and need to find a suitable replacement. On the printset it is
> described as "D 672 TR=14NS PIV=60V SI".
> What would be a suitable replacement?
> There is a local Maplin that would be open today that has this one:
> http://www.maplin.co.uk/switching-diode-46386, would that be suitable?
(Sending again because I sent it from the "wrong" account, apologies if this
The saga of my broken PDP11/24 PSU (H7140) continues. I have now found a
shorted diode and need to find a suitable replacement. On the printset it is
described as "D 672 TR=14NS PIV=60V SI".
What would be a suitable replacement?
There is a local Maplin that would be open today that has this one:
http://www.maplin.co.uk/switching-diode-46386, would that be suitable?
On Thu, 26 Apr 2012 06:15:06 -0500, cctech-request at classiccmp.org
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>> I'll say. The kind that can buy into a phrase like "Cryogenic
>> processing renders the Reference-II absolutely grainless."
>> I read that as "brainless" at first, and I still think that's
>> what they meant.
> There were some classics sold (?) over here.
> Like 'carpet earthing clips', of which yuu must always use an odd
> so that more charge runs away than comes back.
> Or electret foils. I have no problem with the existance of electret
> or indeed of its use in audio (microphones). Butsticking an odd
> number of
> trianges cut from it on your record turntable, pointing in the
> of rotation would, IMHO, make no improvement tot the sound.
> Or cuttint the corner off your amplifier front panel (appearmetn and
> number of corners sounds better).
> And we all rememebr the green pen :-)
On April 1, 1962, Swedish Television had an item on the news where a
well-known technical expert explained that the broadcasting company had
just installed new equipment which would allow viewers to see the
programmes in colour, if they cut up a ladies' nylon stocking and fixed
it over the screen. I believe quite a few people actually tried it.
It became one of the best known April Fools jokes in Sweden, at least
with those who were around at the time.
A friend from Tucson, Arizona, is selling all his books since he will be
moving soon. Since his collection includes some computer classics, I
thought there might be some interest here.
I have an HP9836CU (series 9000/200) without monitor cable.
The computer seem to boot up, the monitor, when powered, has no
The cable (15 pin Dsub male to male) is pin to pin ? all pin used ?
I'm going to build the cable, but I'm not sure about pinout
There is a service manual with circuit diagrams ?
I've found only the manual on the HP Australian museum, but is a board
Thanks in advance
Alberto Rubinelli Mail : alberto at a2sistemi.it
A2 SISTEMI Web : www.a2sistemi.it
Via Costantino Perazzi 22 Tel 0321 640149
28100 NOVARA (NO) - ITALY Fax 0321 391769
Skype : albertorubinelli Mobile +39 335 6026632
MUSEO DEL COMPUTER / COMPUTER MUSEUM
http://www.oldcomputers.it Mail:info at oldcomputers.it
Tel 0321 1856032 Fax 0321 2046034
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