1964 Antique MODEM Live Demo

[Ethan Dicks]

On Fri, Jun 5, 2009 at 11:21 AM, Jochen Kunz <jkunz at unixag-kl.fh-kl.de> wrote:
> On Thu, 4 Jun 2009 15:15:24 -0400
> Ethan Dicks <ethan.dicks at gmail.com> wrote:
>
>> We had something like that happen with our Qbus COMBOARDs when an
>> early customer installed theirs into a Qbus backplane that didn't
>> provide -15V (which is, ISTR, most of them).  Things didn't make sense
>> until we figured out the lack of negative voltage to the 1488s/1489s.
>> Every Qboard after that had a DC-DC converter on it (and I still have
>> dozens of those, new on the slab of foam).
> Even DEC did it. The, IIRC, DHV11 QBus 8 line RS232 has a DC-DC
> converter on it. I saw several DHV11 where the poted torroidal
> inductivity of this discrete DC-DC converter was ripped of the PCB.

I think our issue (and maybe DEC's as well), is that old (16 bit?)
Qbus backplanes provided -15V, but not the BA23 and newer.  I might be
mistaken, but we did start Qbus product development before we had a
MicroVAX-I on site.  We tested with a 4-slot LSI-11 box (and the Fluke
9010A I was talking about last week) for initial functional testing
(CSR bits, DMA, local RAM/ROM, etc.)

I do remember that the Rev 0 board had a DC-DC converter attached in
dead-bug mode.

-ethan