11/45 - unjustified progress

[Jay West]

Well, I dug in to the prints for the RL02 and wrote up notes for myself on 
all the signals feeding the fault lamp and exactly what pins of what chips 
they were on (E1 and E2 of the drive logic board). Went downstairs and 
pushed the BA11-K back into the rack (I had it out to check the ACLO & DCLO 
signals). I pulled out the RL02 and lifted the logic board and got my notes 
ready. Instead of a logic probe I decided to use a logic clip. Easier & 
quicker in this case because I knew just what pins to look at on which 
chips, and all the signals of interest were on two adjacent chips.

I powered up everything including the RX02. When I hit load, the drive spun 
up and came ready. No fault at all. The RL02 and RX02 both boot & work fine.

I've never been quite so disappointed that a system worked, because I know I 
did nothing to fix it. I tried to recreate the problem all afternoon - with 
the machine cold, or with it running the instruction set excerciser for 
hours, no hiccups. The odd part is, the "RL02 faulting upon spinup IFF the 
RX02 is powered on" WAS completely reproducable, and it never once failed to 
fail. It failed absolutely 100% of the time for the past few weeks. Not only 
if it was on when the RL02 spinup was attempted, but if the RX02 was off and 
the RL02 spun up successfully - the moment you would apply power to the RX02 
the RL02 would immediately fault. Now I can't get it to fail, and all I did 
between times was extend the BA11-K, hook up a probe and look at a few test 
points, then put it back.

Perhaps it is cables. I'll be trying again tomorrow to reproduce the problem 
and hope it reoccurs :\

Jay