HP2100A luser questions

tony duell ard at p850ug1.demon.co.uk
Fri Nov 21 12:58:16 CST 2014

> > 12531-60022 Buffered TTY Reg (2 off) looks to be current loop and RS232 serial
> Those should be 12531C's, they should have 225.28 KHz crystals, intended for 110 baud operation.
> Changing the crystal to 307.2 KHz should change it to a 12531D, for the standard baud rate series, if desired.
> These are the common console-device interface.

Yes, I have checked the (plug-in) crystals, both are the 225.28kHz ones. So I guess 110 buad for a Teletype.

I have downloaded the manual from the Australian museum site. I think it would be easy to hack them for
other baud rates if necessary, the 307.2kHz crystal not being easy to find, but 8 times it is. 

According to the manual it can link to an HP2752A teleprinter. I have downloaded the HP part of the manual
on that too, it's an ASR33 with 'wiring changes' Alas the manual doesn't describe exactly what the changes are.
It does give the schematic, though. One change is obviously to fit the reader control PCB, but there may well
be others. 

According to the 12531 manual, the interface is current-loop-like to link the HP2752A (it may well not be 
standard enough to work with other devices), but there are extra transistor circuits on the board that can
be linked in with jumpers on the device edge connector to make it work with EIA (RS232) signals. Which 
sounds useful

> > 12592-6001 +8 but Dup Reg (8 bit parallel for paper tape punch/reader?)
> yes

This seems similar in concept to the HP11202 interface that I know well from my 9800s. In that 
it only has one set of strobe and flag lines for both input and output. So alas I don't think it can 
be used with both a punch and reader at the same time. Oh well...

FWIW I rescued this machine from a skip (dumpster) many years ago. With it were an HP7900A
disk drive (although no PSU for it) and an HP2748A tape reader. The last I have got working [1].
I was going to use the drive with my 9830 (and probably still will) -- I have now got the PSU

[1] If you take one of these apart you _need_ the alignment madrell. It's easy to turn one from
steel rod, but without it you will never get the motor positioned properly. It will seem to run but 
will be wearing the clutch parts.

> > What is Current Transfer Logic, the machine seems to be full of such ICs?  Any data sheets,
> > etc out there?
> The 2116,15,14 and 2100 used Fairchild CTuL, along with some TTL.
> The family name is actually "Complementary Transistor MicroLogic".

Yes, I was foolish enough to see 'CTL' in the HP parts lists and then look that up on google. I now
realise my mistake. I have found some data on CTuL on the web.


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