[volt-nuts] Newbie here...

[Bob Albert]

Pete,

The EI is in three parts connected by many massive cables.  When I say it's pretty close, I mean it agrees with everything else I feel is close.  The 3456A has a -12V reference which the EI measures at -12.0026 or so.  It uses an oven so it takes a half hour to settle.  I have pics of the panel and would post them if I knew how.


The Valhalla is actually a good meter but one range has a small problem.  The Racal-Dana is unfixable because I can't find a manual, short of spending more than the meter is worth.  Those two units are very similar; the main difference is 1) the Valhalla measures AC current and 2) the Dana has a very sensitive DC microammeter such that I can measure diode leakage.

I am befuddled by the HP3456A.  I have replaced some parts but so far it's not doing its thing.  I have the manual but it sucks, not having a proper schematic diagram nor a board trace layout.

The Calib Stds unit is nice, a manually operated slideback DC volts only unit, compact and easy to use.  Again, no manual available and, in fact, no mention of the company anywhere online.  They were in Los Angeles area.

The main reason I want to fix these is that I hate owning anything that doesn't work.  And I like knowing my meters are accurate as well as precise.

I also have some 10V reference ICs that have been around here a few years.  They all agree within a few mV.  I made a permanent reference out of them with a switch to select each, and they are running whenever I am in the lab.

Bob




On Saturday, February 22, 2014 6:31 PM, Pete Lancashire <pete at petelancashire.com> wrote:
 
My take

HP 3456A - Great meter. Manuals on the web. Has at least one HP custom
device that is a problem,  other then salvaging from anohter 3456A is
unobtanium. The most complex of your collection.

Valhalla 4440. Other then for the fun of fixing stuff not worth anything.

Racal Dana 4200 Don't know it

EI 3000. I don't have a 3000 but do have a lower cost variant. At least to
me a collectors item. You say "pretty close", pretty close to what ?  I
believe it was EI that originated feedback in the Zener loop, finally
getting rid of the chopper. If anything the reference by now should have
settled down :-).

Depending on your experience in repairing T&M, I'd use the Valhalla as a
way to get some. Then get a manual for the 4200 and repair it. Finally dive
into the 3456A.

Love to see some inside pictures of the EI.

-pete




On Sat, Feb 22, 2014 at 5:35 PM, Bob Albert <bob91343 at yahoo.com> wrote:

> I am the owner of a few fairly accurate and/or precise voltmeters and
> would like some information if it's available.
>
>
> First, my Electro Instruments model 3000 5-digit antique with Nixie tube
> readout, and the accessory AC converter.  It hasn't been calibrated in
> decades but seems pretty close.  I have no manual.
>
>
> Second is the recently acquired, not working HP 3456A.  Struggling with
> that repair.
>
> Third is the Valhalla 4440.  I have most of a manual but it differs
> somewhat from mine.  Mine has an issue on one range of volts.
>
> Fourth is the Racal-Dana 4200.  This works fine but after it warms up for
> a half hour starts to get erratic.
>
> Fifth is a Calibration Standards model DC-110A.  No manual.  It has some
> trouble on range overlap.
>
> Can anyone help me with any of these units?  Documentation, reputation,
> etc.  Photographs supplied if needed.
>
> Bob
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