One more try - Can you ID this S-100 Serial board?

drlegendre . drlegendre at
Thu Oct 1 18:21:34 CDT 2015


That's an intriguing and very real possibility, but then there's this: - Does that logo look familiar? Founded in the 80s,
controller boards, interface modules, single-board computers.. but yes,
they are in Germany. I did try contacting them, but never heard back.


To answer a few questions:

Yes, I am certain this is an S-100 board. It was pulled from the Altair I
rebuilt and the PO confirmed that he "had a terminal or something"
connected to it.

The burned area on the board is where a couple of zener regulators gave it
up. You can maybe see that I've replaced them with 3W zeners and 1W
resistors. I believe these create +/- 12V supplies for the op-amps and
RS-232 levels?

I did some tracing on it, not my cup of tea, but I did learn some things..
here's what I found: Each of the two 10-pin headers (I'll call these serial
ports) seem to be wired the same, with duplicate component setups for each

Pins 4 & 6 connect via 175R and 47R resistors, respectively, to one input
of an XNOR gate on an LS266 chip. Second input to same XNOR gate seems tied
to Vcc via jumpers. Output of XNOR gate has 1K pull-up to Vcc (open
collector output) and then connects to pin 20 on the 1014/15 UART which is
"SI". So pins 4 & 6 seem to be our serial inputs (RxD) with two different
series resistances offered (175R or 47R). Might be an input voltage divider
or termination option?

Pin 1 connects to the collector of a 2N3906 which is in turn driven by the
output of one section of an LM1458 op-amp. The non-inverting input of the
op-amp connects back to pin 25 on the UART, which is "SO". I'm not sure
what the inverting input of the op-amp is tied to.. perhaps it's part of an
enable circuit? But it seems pin 1 is our serial output (TxD).

The other port pins are variously tied to resistors, jumpers and/or 74XX
logic. These might be our handshaking lines, ring detect, etc.

That's all I know so far.

On Thu, Oct 1, 2015 at 3:30 PM, Chris Elmquist <chrise at> wrote:

> I've got another theory regarding drlegendre's board.
> I happen to know via out-of-band information that he is here in MN.
> There is a company in the Twin Cities called Micro Component Technology
> that existed in the 70s, 80s, 90s and still today.
> They make handling and test systems for IC fabrication.
> I'm willing to bet dollars to donuts or lingonberries to lefse that his
> board is a custom job made by the MN MCT and it went into the computer
> control of one of their machines from the early 80s.  Something probably
> designed in the mid to late 70s.
> The logo on the board matches what I remember seeing on their building
> in Shoreview ages ago.
> I don't think it's the MCT that made PC (as in IBM PC) plugins...
> Chris
> On Thursday (10/01/2015 at 10:14AM -0500), Jay Jaeger wrote:
> > I had a look, and it seems to me that there is more going on on this
> > board than just serial ports.  It is even possible that the system it
> > was in had essentially re-purposed the board to use for a serial ports
> > in a way that the original designer did not intend.  That would explain
> > the lack of obvious level shifting - it may have been used for TTL level
> > serial I/O.
> >
> > Also, there are lots more passive components on this board than I would
> > expect for a serial interface board.
> >
> > A company with these initials made EPROM programmers, though their logo
> > was different - but perhaps it changed over time.  Maybe this was a very
> > early interface board to one of their very early programmers - and
> > perhaps it is missing some of the parts, like connector headers and
> > resistor packs, and then was re-purposed.
> >
> > JRJ
> >
> > On 9/30/2015 7:52 PM, drlegendre . wrote:
> > > (Months along, posts to several boards / lists, still no help on this
> one..
> > > so I'm giving it another shot. I'd really like to use this board)
> > >
> > > Been trying to no avail to find any info on this 'MCT' S-100 serial
> card.
> > > I'm pretty sure the card works, as it came from a previously-working
> system
> > > - but all documents are missing, and without the info, I have no idea
> how
> > > to put it to use. Photos are here:
> > >
> > >
> > >
> > >
> > > Other than what I believe is an artwork / batch number on the rear, the
> > > only marking is "Assy 105510" on the front silk screen. My hunch is
> that
> > > this may have been a fairly generic 'OEM' type card which could have
> been
> > > re-badged and sold under one or more different names. So perhaps the
> docs
> > > exist under a name other than MCT?
> > >
> > > Any help greatly appreciated - thanks!
> > >
> > > -Bill
> > >
> --
> Chris Elmquist

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