Successful Repair - RLV11 put in an AB/AB backplane
Lou
backplane. I've never seen a post on this, so I thought my experience
might be useful to someone else out there in the same situation.
As we have been warned, the two card RLV11 must be in an AB/CD
backplane, usually BA11-S, where the whole right side of the backplane
is the CD interconnect. The M8013 and M8014 must be placed next to
each other, with the 13 on top (closest to the procesor). When placed
in an AB/AB backplane, the magic smoke is let out and the controller
no longer works. The problem is that power pins on the rightmost AB
slots get connected to signal lines intended to be on the CD
interconnect. I just repaired a controller subjected to such a
horror.
I found that the M8014 was unharmed.
The M8013 however was not so lucky, but the repairs were not that bad.
Of all the trouble that could be caused, the injury occurred when what
should have been CD2 that carries the 8.2MHz clock was connected to
AD2 (+12V). The path of destruction can be seen on sheet 3 of the
M8013 schematic. I found E31 (74S74) to have burned up so bad that its
case was cracked and traces on the board were melted open. Upon
rebuilding the traces and replacing E31, I also found that E20 (74S00)
was blown, and lastly, Y1, the 8.2MHz full can TTL clock oscillator.
When these were replaced, the controller returned to life and all was
well again.
I hope this helps someone else out there in the same situation.
Lou
Lou
paragraph. I should've typed BA11-N not BA11-S. The N was the AB/CD
backplane.
Lou
Dave McGuire
> I just repaired an RLV11 that was smoked by being put in an AB/AB Qbus
> backplane. I've never seen a post on this, so I thought my experience
> might be useful to someone else out there in the same situation.
Well damn, thank you for that, I've saved that away!
Exactly that happened to me with a borrowed RLV11...yes, borrowed.
It was around 1985 so they were still pretty pricey, I was maybe
sixteen, and a friend brought it over so I could load up a new system
disk. I didn't know about the Q/Q vs. Q/CD problem. Magic smoke came out.
I was horrified of course, as there was no way I could afford to
purchase a new RLV11 for my friend. He told me to forget it and we
chalked it up to experience. I still cringe when I think about it.
-Dave
--
Dave McGuire
Port Charlotte, FL
Bill Gunshannon
I actually have a pair of them that have that problem. Don't
even remember where I got them at this pioint. Being a packrat
I have never thrown them out expecting that one day I would have
the time to troubleshoot and fix them. In this case, there was
no externally apparent signs of a problem so I always assumed it
was going to turn out to be some buffer chip on one or two QBus
lines that were fried. Now I have something to work with. Of
course, I still don;t have the time, but that is another matter.
Soon, real soon........
bill
--
Bill Gunshannon | de-moc-ra-cy (di mok' ra see) n. Three wolves
bill...@cs.scranton.edu | and a sheep voting on what's for dinner.
University of Scranton |
Scranton, Pennsylvania | #include <std.disclaimer.h>