phil@eos.UUCP (Phil Stone) (01/23/90)
I've had repeated problems apparently blowing out lines on one of my 8520's. How this happens I'm not sure...I may have gotten careless plugging or unplugging things into the joystick port while powered up (and I swear I'll NEVER do it again, heh). Usually, the problem goes away when I replace the offending chip (U300, I believe, which is used for the parallel port and some of the joystick port lines). However, this time it *didn't* change the behavior of the problem - the FIRE0 line is always asserted (the mouse fire button always thinks its down) and my printouts come out with bad characters (mostly "e's" in place of the desired character, but other transpositions as well). Now, the possibility exists that I may have been sold a bum chip, but otherwise, I'm stumped. It doesn't appear in the schematics t at any circuitry is in between the 8520 and the joystick fire button or the parallel port. I also can't see any relation between these two functions (FIRE0 and printer lines) so this seems to be a very strange coincidence. Anyone have any ideas? Chuck? Phil Stone (phil@eos.arc.nasa.gov | ames!eos!phil)
phil@eos.UUCP (Phil Stone) (01/23/90)
Sorry. I need to clarify what I just posted... In article <6025@eos.UUCP> phil@eos.UUCP (Phil Stone) writes: >I've had repeated problems apparently blowing out lines on one >of my 8520's. [. . .] >[. . .] the FIRE0 line is always asserted >(the mouse fire button always thinks its down) and my printouts This is probably quite confusing. I forgot to mention that I'm reading a track ball off of the SECOND joystick port, and *its* fire button is the one that seems stuck down (the trackball works fine in the first port, btw, so I know it's not the problem). Phil Stone (phil@eos.arc.nasa.gov | ames!eos!phil)
collins@pnet02.gryphon.com (Steven Collins) (01/24/90)
When I suspect my A1000's 8520s, I switch them and evaluate if the
symptoms change. If so, one of the 8520s is most likely bad.
It is very easy to munge the traces under the 8520 sockets if you remove
the chips with a screwdriver instead of a chip puller, so you might take
a close look for this as the source of your problem...
steve collins
UUCP: {ames!elroy, <backbone>}!gryphon!pnet02!collins
INET: collins@pnet02.gryphon.com