HP 12653A line printer interface

David Collins davidkcollins2 at gmail.com
Sun Jul 16 18:54:06 CDT 2017

I do indeed have the printer. Found it on the weekend. No sign of the interface card or cable yet though. 

David Collins

(Sent from out of office)

> On 14 Jul 2017, at 6:02 pm, CuriousMarc via cctalk <cctalk at classiccmp.org> wrote:
> Ah, thanks, I learned something. The HP 2767 is a weird beast - line drum
> printer but only 80 columns, from what I glean from hpmuseum.net. David
> (Collins), do you have the printer?
> Marc
> -----Original Message-----
> From: J. David Bryan [mailto:jdbryan at acm.org] 
> Sent: Tuesday, July 11, 2017 11:12 AM
> To: CuriousMarc
> Cc: Classic Computing List
> Subject: Re: HP 12653A line printer interface
> Marc,
>> On Monday, July 10, 2017 at 22:24, CuriousMarc wrote:
>> I thought I did, but what I have is the HP 12845B Line Printer 
>> interface card, for which I could find the documentation.
> Thanks for checking.  Yes, that does seem to be the more common card.  As
> far as I know, the 12653A was used only for the HP 2767 (a rebranded Data
> Products 2310), whereas the 12845B was used for a number of other HP
> printers.
>> Reading some more, it is meant for the 2607/261x series of printers, 
>> which apparently use a narrower 7 bit interface (the 12566 is a 16 bit 
>> interface card).
> Which is all a bit odd, as the 2767 also uses 7 bits for data.  Unlike the
> other printers that use differential interfaces, the 2767 uses single-ended
> TTL-level (more or less) drivers and receivers, which may explain the use of
> the microcircuit-based interface.
> The 2767 signal drivers are adjustable for a 3- to 8-volt output level, so
> perhaps the 12635A "modification" was to clip the inputs to avoid damaging
> the standard microcircuit receivers (7400 TTL with an absolute maximum input
> spec of 5.5 V).  In the absence of a manual, I was hoping that a photograph
> would reveal the modification.
>> But maybe you can inspire yourself from it.
> The existing 2767/12653 simulation was reverse-engineered from the
> diagnostic and OS drivers.  Although it works, I was hoping for something
> more authoritative so that the code could serve as a reference for the
> now-extinct hardware.
>                                     -- Dave

More information about the cctech mailing list