PDP-11/45 RSTS/E boot problem

[Peter Coghlan]

Jeffrey S. Worley wrote:
> 
> Back in 2000-ish, I was upgrading my DG MV4000/dc to 8mb so as to be
> able to run the snazzy AOS/VS II tapes I'd got along with the 9 track
> drive I hacked onto the machine...
> 
> The install would start and then bomb at a certain point every time.  I
> decided to work the machine hard and then pull the board and give a
> good SNIFF.  This is a 15x15 inch board populated with 256kx1 drams. 
> The time in the machine got the board cooking nicely, and when I
> smelled a certain charred smell in the vicinity of a 74ls04, I knew it
> was that magic black smoke.  I pulled a 74HCT04 from a known-good isa
> card, socketed the spot and viola!  Working 8mb board.  It isn't
> ALLWAYS the most expensive chip, thank God, and sometimes even us not-
> as-bright guys come off with a win.
>

About 20 years earlier than that, one of my friends at school asked me to
fix his Jupiter Ace which had stopped working.  I told him I didn't hold
out much hope for success because I didn't have the vaguest idea how his
little machine worked at that time but I agreed to wave my multimeter in
the general direction of it's power supply.  I opened it up and quickly
found that the voltages seemed very reasonable and I prodded around the
board rather aimlessly looking for some part that looked guilty.  I soon
noticed that one of the eight identical chips in a row at the bottom of
the board was getting hot enough to burn my finger while the others
remained cool and calm.  I can't remember where I got a replacement 4116
or 4164 or whatever it was - I probably had to get it mail order but once
it was soldered in with fingers crossed that nothing else was wrong, the
machine came right back to life.  Sometimes you just get lucky.  I wish I
could be that lucky with some of my own stuff now.

Regards,
Peter Coghlan.