13 Aug
2013
13 Aug
'13
10:59 a.m.
On 2013 Aug 13, at 4:15 AM, Chris Elmquist wrote:
On Tuesday (08/13/2013 at 08:46AM +0200), Pontus
Pihlgren wrote:
You'll notice the associated selector knob that says "margin select".
AIUI, (I don't have direct experience with said machine), this and
the voltage adjustment would be used during preventive maintenance to
uncover components that were operating near the margins. Adjust the
voltage around the upper and lower operating limits, see if a problem
show up, then go looking for the failure. Better to uncover the
failure during PM than during operating time. I could imagine it
would also help with finding an intermittent, in that adjusting the
voltage slightly may force it to a constant failure.
I expect the adjustment goes back to do an 'indirect' adjustment of
the regulated supplies.
Last time I saw an object for sale was a KI front panel:
http://www.ebay.com/itm/Vintage-DEC-PDP-10-KI-10-Computer-Console-
Panel-Super-Rare-/130768694290
Interesting pictures. I am curious why machines of this era often
have
a "VOLTAGE" adjustment on the front panel? Was it really neccessary
for an operator to adjust some voltage setting as the machine ran thus
requiring that adjustment to be easily accessible on the front panel?
What is it about the design that requires this?
Why wouldn't the voltage adjustment be on the back or down inside
where
some knob twiddler can't get to it?
It looks like the knob turns a variac so it's adjusting an AC voltage
while the meter reads DC... so is it perhaps adjusting the AC mains
input to a/the power supply, because the mains voltage wasn't stable?
The variac seems a little small for that but ...
Curious.