4 Sep
2007
4 Sep
'07
5:11 p.m.
Quoting J Blaser <oldcpu2 at rogerwilco.org>:
So, I guess it's a 'dynamic' issue, rather
than a static one. Maybe the
load does matter. I'm going to try that next.
Success!
Well, well, what do you know! A load does indeed make
a difference.
As suggested earlier (thanks guys!), I tried to scrounge
around for something that I could use to load the PS. I
thought I had a few vehicle headlamps, but short of
stealing a couple from my car, I came up short.
Hmmm...<thinking to myself>...why can't I just use a
regular household lightbulb? They're designed for 120v
(or, as Tony pointed out, actually peak voltage of 170),
right? I didn't expect to see light at just 24 or even 42
volts, but I figured I could easily replace a $1.98 light bulb
if things went bad for me.
Sure enough, just that simple addition to the circuit put
things right. I read 27.5v and 11.5v on the two outputs
in question. (And, no, I saw no light.) Though these
voltages were not exactly spot on to the 'spec', they
were close enough to convince me that I'd be safe
attaching the PS to the PCBs.
I took the plunge, and things are looking just fine. I'm now
reading 24.8v and 9.7v with everything connected, which
are pretty close to 'spec'. So, I guess there is some quirk
in this particular PS that lets the voltage 'runaway' when
not loaded.
Even so, I'm now a happy camper with my incredibly
powerful PDP-11/03 running with 64KB and four (count
'em....four!) RX01 devices for total storage of just under
1MB! That'll knock the socks off my neighborhood high-
school computer whiz! I'll be the envy of town! ;-p
Many thanks to all that helped me work through this.
- Jared