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