1 Oct
2014
1 Oct
'14
1:30 p.m.
I had exactly the same thoughts. +5v is also the same
pin as it is on
Unibus; Qbus shares Unibus' defined +5v and GND pins and adds a few more
dedicated grounds (MUB is a different matter, of course). I'm honestly
a little surprised they didn't make the power pins a little more broadly
compatible (or at least less likely to cause damage) in general, but
presumably it was a matter of many different engineering teams working
on different standards over many years.
Reminded me, alas, of the time when I was younger and evn mroe foolish
and repairing an RK11-C. I had pulled one fo the namy flip-chip cards to
inventigate it, and decided to power ir up by stickign it in a slot in an
otherwise empty Unibus backplane that was conencted ot the PSU. +5V and
Groudn were in the right places, I'd checked that.
WHat I had not spotted was that there's -15V on pin B2 of said
connectors. And this was a logic input on the card I was testing (I think
it was the carry inptu to a 7482 adder, it was certainly _an_ input to a
7482).
RIP 7482, not an easy chip to find.
-tony