Such luck!  Welcome, things couldn't be better for you, for this type
of fascination.

At 02:51 PM 4/26/2011, Fred wrote:

Best Wishes,

Marv Gozum
Philadelphia

Hi Fred,

Looks like you got lucky with such a nice collection being offered.

I am confused on why additional zeners would be added to the 731 and 845.  Both
were made to work without batteries.

The 731, if it is in good shape, is an extremely stable reference source.  Well
able to transfer a known value from a competent calibration Lab to use for
establishing the value of your Guildline cells.

As I am sure you know, the 845 is the only high impedance DC NULL meter available
that was worth a damn.  The first mains power transformer (and battery with its
charge circuit) is just to supply a power source for the 84 hertz transistor
inverter to the neon's.  That same inverter is also used to power the all of the
circuitry.  That is part of what provided the extremely high input isolation.
The noise you see on the 1 uv scale is normal.

The 720 switch problem sounds interesting, I wonder what caused the switches to
be so bad ?  In a clean environment there should be no reason for them to have
disintegrated.

The Guildline was a very nice catch.  Have you had an opportunity to determine if
the cells are in good shape ?  Hopefully nobody loaded them with a low
resistance, that would have messed them up for sure.  In conjunction with the
845, 750 and the 731 you have yourself a nice voltage reference system.

As for cables, well, I would not worry about that.  Just use normal copper wire
and you will not go wrong.

845 ?

73....Bill....WB6BNQ

Fred wrote:

I think I have the manuals complete, they are original and I do not miss
pages but maybe there is also a real extended service manual for the
845AB.
In my schematic there is a A and a AB powersupply schematic. The A has a
zener and no battery. They removed the battery in mine, that was also
written on the cabinet and placed two zeners. I think they did not get
it right anymore and then bought the Fluke 8500 that was part of the
setup (in the drawings I had in the documentation it was coupled to the
750)

Tonight I did some first measurement. The Cells are now about a month or
two operational and heated. They are very carefull moved to a special
made shelf two weeks ago. But now I have a problem. It's like the man
with just 1 clock, he think he does know the time, the man with two
clocks has a problem. I have 4 DC calibrators and 4 Weston cells so I'm
lost :-)

I first measured 1 cell from the Guildline using the 845 and the 731. I
turned the 731 dial until I had a zero in the 3uV range and allmost zero
in the 1uV range. I took that value as a reference. Following the trend
in the graphs from this cell (from 1977 upto 1987) the value could be
realistic. The oven temp is 30.07 degrees. The philips was about plus
250uV, the 332 was minus 160uV. But if I connect them through the 750 I
get a 25uV difference. I have not tried to calibrate it, it is always
kept in the same clean room and never messed around so it will be
probably better if I leave it like this because the 720 is not usefull
and needed for calibration.

The 720 is strange, it is clean as a baby inside-out. It is not been
dropped or so. But all the plastic is cracked and broken. If you touch
it it crumbles. Maybe someone back then cleaned it with some solvent.
It's a pitty because it is a beautifull instrument. I must find some
teflon or poly-ethilene to make new ones (I have a lath and a mill but
is is a lot of work) Some are possible repairable using 2K-epoxy. One
switch, number 1 from right, is very bad, I had to take it out because
the centre-follower is crumbled. The others still work and are in place
but the studs have cracks and pieces allready missing.

73

Fred

WB6BNQ schreef op di 26-04-2011 om 13:20 [-0700]:

Hi Fred,

Well, it sounds like the people that had this equipment really had no idea how to care
for it properly.  It also suggests that they did not know what they were doing and just
bumbled along.  Could be the reason the operation was shut down at some point.

No special manuals exist for the 731, 845 or for that matter most of all of the old
Fluke equipment.  Any inside understanding was gained through experience.

The best method you have for comparing against the cells is to use the 750A divider.
This divider is very high quality and hopefully the previous owners did not go inside
it.  The only truly accurate and stable output on the 731 is the 10 volt posts.  I
would hook up the cells and the 845 to their respective connections on the 750A and
then attach the 731's 10 volt posts to the divider string's main input terminals (as
shown on page 2-5) with the switch set to 10 volts.  Then do your inter comparisons
with the different cells in the Guildline.  You can use the cell voltage level switches
on the 750A for determining the cell values with the 731 acting as the reference.

The best you will be able to do (unless our 731 is calibrated) is to determine
differences between cells.  By taking readings several times a day over many days and
weeks you can get a picture of the cell activity and their stability.

If your Fluke 731 is not calibrated, hopefully you may find a known quality Cal Lab
that would provide you access to adjust your 731 to a known value.  Then that would
become your main reference.  Then you could assign values to the cells in the
Guildline.  From that bootstrap you should be able to arrive at a confidence level to
trust what is happening with the Guildline and eventually make it your Lab reference.
Or at least make the Guildline a faithful sanity check.  The problem with cells is you
need to constantly inter compare them to make sure they are behaving correctly and
remaining stable.

As the equipment, presummably, has not been compared or adjusted against a real
standard, I am not surprised by the offset readings you measured.  The best stable
voltage reference you have is the Fluke 731.  It would be well worth the expense to
have it calibrated with a high quality Lab if you have one near you.

Regarding the 720, Fluke was making those until just very recently.  I would see if
they could still provide you with the necessary parts to rebuild it.  It would be well
worth the effort in my opinion.

73....Bill....WB6BNQ

Fred wrote:

In message 1303856302.1630.51.camel@Fred-asustower, Fred writes:

We see this kinde of thing happen in computer museums too, it's a
production fault: It took some time until the plastic industry found
long term stable additives.

This is also why serious museums worry a lot about their barbie
doll collections.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

Is there a way to decipher plastics potential longevity in a finished
product?

I'm impressed plastic parts on many HP equipment endure intact over
20+ years, some barely discoloring.  I can't tell what type they are,
but the more durable plastics often feel hefty and solid.  Likewise,
Fluke DMM have the same 'feeling' and endure for decades.

On a side note, casing of some iPhones barely 2-3 years old are
spontaneously cracking, so it can be made quite badly too.

At 01:37 AM 4/27/2011, Poul-Henning Kamp wrote:

Sincerely,

Marv Gozum
Philadelphia, PA

The only real way to tell with plastics is to subject them to the test
of time and environment.  The basic problem is one of plasticizer migration.
Many plastics have an added goo that improves the way they flow in molding,
and softens the plastic so that it is suitable for use.  The plasticizer
evaporates slowly out of the plastic making it shrink, and leaving it very
brittle.  Some plasticizers migrate to the surface leaving the plastic very
sticky... vinyl (PVC), particularly soft vinyl, which is heavy in plasticizer,
has that problem.  That plasticizer migration is what makes xerox'd pages
stick to vinyl binders, leaving the lettering behind on the vinyl...

Some of the ancient plastics aren't really plastic at all... bakelite is an
example.... and they hold up incredibly well.  The common characteristic,
in my opinion, no plasticizer.  The much fabled BPA is one of the plasticizers
that causes problems if it isn't used just right.... It also causes breast
development in men, but that is another story.

-Chuck Harris

Marvin E. Gozum wrote:

I have removed one switch. I have measured the resistance at 500V from
the (cleaned) original material and that was much lower as a same lenght
of teflon. (but the Teflon was very hard to measure, if I came closer
then a meter to the HP4329A the meter jumped around, the needle was
almost max left in the most upper range at 1000V so we are talking
penta-ohms, I'm not only a volt-nut ;-) ).

So I made out of teflon a shaft-to-rotor coupler. A hell of a job. took
me two hours  milling and turning the lath but then it fitted like a
glove. Then I made 12 teflon studs. I drilled a 4mm hole and with a
little tool I made I could press in the old inserts. The switch is
already in its place.

But I noticed a strange thing. The stud that was broken in to pieces was
hard and brittle. One insert was still in but just a little hit with a
screwdriver and it broke in two.
The other stud was still in one piece. But I did not want to take a risk
so i thought, lets replace this one too. I gave it a gentle hit but
nothing, took a pair of pliers squeezed as hard as I could, nothing.
even with a cutter, it just left bitemarks but no breaking. After all
this violence I had to replace it but I think there was nothing wrong
with this one. I heated it and then I could pull the inserts out.

So this is weird, almost all studs are gone to dust but some are as
strong as new. The problem is, to test it I have to use force and that
weakens them so I exchange them all to be shure.

But making 5 extra new rotors is a hell of a job so I will check the
rotor couplers optical very careful for cracks and leave them. The
reason the studs break when the plastic get hard is because the inserts
are a bit conical so screwing in the bold expands them. So there is
tension in the material. The rotor couplers are just a "lose" fit and if
one breaks I now know how to replace them. Not much work. The broken
coupler was coupled to a floating one rotorswitch  (both studs complete
lose) so maybe a shock during transport.

I also mailed Fluke here in the Netherlands. Got a mail back from the
service desk they forwarded it to the service manager. If they can
supply new rotors and studs (affordable)  that is even better, I like it
to be original.

Now I am going to find out if there is a affortable solution to
calibrate and adjust the 731A. I spoke someone who had a Tek current
scope probe calibrated and adjusted, That was allmost 500 euro. To much
for me.
After that I can compare them with my Guildline. (if I remember well the
10V is not adjustable but I have the manual so I will look that up
first)

Fred

Chuck Harris schreef op do 28-04-2011 om 10:36 [-0400]:

Thanks Chuck, that's very informative.  That pretty much describes
the life cycle of a lot of old plastic I've encountered.

You say evaporate, is possible then to seal plastic parts to prevent
plasticizer migration, and prolong the parts life, even if its
already old but still has not fallen apart?  Add any kind of
plasticizer to revitalize old plastic?

Yes, vinyl binders seem to almost weep something, that doesn't seem
good!  I see Bakelite endures over time, but it very ceramic like and
tends to cracks if dropped.

Sorry all, at most this should be discussed at the HP forum group, so
this is my last topic digression on the volt-nuts forum.

At 10:36 AM 4/28/2011, Chuck Harris wrote:

Best Wishes,

Marv Gozum
Philadelphia