[volt-nuts] introduction

Fred pa4tim at gmail.com
Tue Apr 26 18:51:40 UTC 2011


My name is fred, PA4TIM, I'm a volt-nut. Took a lot of therapy to
confess ;-)

I was already fascinated by calibrations because I restore measurement
equipment. I collected some old calibrators like an old one from Philips
using nixies as indicator, a Tek AC calibrator ment for internal factory

But a few months ago a got a mail from a stranger who noticed my website
and asked if I was interested in the stuff from his companies old
calibrating lab (for free !!!) The lab was closed 25 years ago, but the
stuff stayed there unused. Now they needed the room and "found" this
stuff but almost nobody knew what it was so a lot was thrown away. He
thought that was a shame and asked if he was allowed to find a
collector. Al stuff including manuals and calibration history and in
state like new. But not used for 25 years and some stuff suffered from
sleeping or was maybe already death when parked away

It started with a Guildline 4 cell unit. In perefect condition. I had to
repair the heater and some minor aging things.

A tek 576 curve tracer came as a bonus with a box new Tek parts.

Then things speed up, if I wanted some more. A complete Fluke
calibration setup. To bad they tossed away all cables.
-332B voltage standard, worked like a charm after changing one cap.
-760A meter calibrator, worked for a week, now constant jumps in
protecting and the home fuse blowes even if I put the plug in powered of
so I think a Y capacitor is leak. I will find that, no problem (I hope)
-510A AC reference standard, dead batteries but I just removed them
because they are optional. I left in the option board. Still not sure if
that is wise.
- 731A, also dead nicads. I removed them and put in a 12V voltage
regulator. Also had to replace a paper-foil capacitor.
- 750A voltage divider. There is room for two strange batteries but as
far as I understand it also workes without as long as you are sure You
do not over voltage
-some HP stuff like a 20 penta Ohm elctro Ohmmeter/voltage source, a
time standard, pindiode modulator and low distrotion sinewave generator.

But then two very important parts of the set up. A 720 kelvin Varley
divider. All see-through plastic isolator standoffs and centre coupling
parts of the switches are desintegrated. That will become a hell of a

The biggest problem was my 845AB, they allready removed the nicads and
added two extra 10V zeners. Thick metal multi-amp ones.  The problem is
the manual is very limited. There are some scope pictures and a small
trouble seek section. 
I had to replace allmost every cap, so did them all. Then I kept
problems with stability. Then I took my lab-supply and put 10V over the
capacitor. It drew about 30mA and was stable. Then I raised the voltage
and when the zener started conducting the 845 draw 600mA. I think the
10V mega-zeners started drawing so much current the transformer
saturated or at least power got unstable. Could not close the top lid,
as soon as it came near the transformer the meter went nuts. I now
placed a 7812 and it is stable over the whole range I think. At 1uV full
scale with shorted input and knob at zero the meter deviated plus/minus
0,1 uV max, most times about 0,05uV. I think that is not bad but this is
my only null-detector so I do not know for sure.

Now I have to find out how to make cables to connect everything, find a
way to determine what will be my  STANDARD VOLT. I have the calibrating
history upto 1988. I can measure the differences between the cells but
first have to find out the safest way, and if that is comform the old
papers I think I take that as a basis. Then adjust the calibrators to
that value. This will probably still be more accurate as the average
multi or bench meter. I have a 6,5 digit as best one.

Does some one has a better way ?

For my collection See www.pa4tim.nl Not all the fluke stuff is on it



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