[volt-nuts] The Fluke 732A DC Reference Standard

[R.Phillips]

Bill
Its interesting that you have reverted to the original AC/DC external supply
connectors - the two 4 mm sockets. My guess is that they moved away from
this set-up as it was probably all to easy to make connections to external
equipment - as the 27.6 volts is also available at these sockets !
Your remarks reference the quickly established stable output is exactly as I
found within 48 hours, remember my instrument had taken a ride in an 
aircraft hold from
the West Coast, USA  to London, UK,  and it still recovered quickly ! The
great difference between the 732A and my 731B's is obviously temperature
stability - the oven makes this a winning factor. In fact I am very
impressed by the stability of the oven, the independent thermistor reads
4.520 K ohms +/- 1 ohm consistently. The move to gelled lead acid batteries
was also an improvement, despite the weight factor - the 731b's were 
frequently
damaged by failed Ni-Cads. And then also the rotary voltage selector switch,
this can be a source of trouble.
Thanks again.
Roy

-----Original Message----- 
From: Bill Gold
Sent: Tuesday, November 05, 2013 3:49 PM
To: volt-nuts at febo.com
Subject: Re: [volt-nuts] The Fluke 732A DC Reference Standard

Roy,
    I have a later manual for the 732A.  P/N 788414 May 1986.  This manual
shows the little 3 pin connector labeled J10 for the battery module.  The
parts list shows a Fluke stock #720844, Mfg 89536 (Fluke) and Mfg P/N
720844.  I have long since removed it from my 732As and replaced it with two
minature banana jacks (2.64mm) red and black.  There seems to be some sort
of Mfg mark on the 3 pin connector but I cannot identify it ( I saved the
old 3pin connectors).  If the manual you downloaded is from the Fluke
website and is named "732A____imeng0000.pdf" or "732A_Users_Manual.pdf" you
will see a "Change/Errata Information, 7/85" list in the front of the file.
Change #5 changes the battery connections to the spade lugs and Change #6
changes the banana jacks to the 3 pin connector.
You were very wise in removing some metal from the top plate to allow plenty
of room for the spade lugs on the new batteries.  I didn't do this intially
and one of the battery terminals shorted to the metal plate and fried the +
18 volt regulator assembly, which took a few days to fix.  My opinion of the
732A vs. the 732B is that since the 732A has been around longer the
references have had a longer time to stabilize.  The only issue I know of
732A vs. 732B is the battery life.  The 732A battery life is around 12 to 15
hours without being powered.  The 732B specs the battery life at around 72
hours.  This makes it easier to get it to Fluke in Everett WA without losing
the "IN CAL" light.  My experience is that even when started from cold after
being off for a long period of time they will stabilze at exactly the
voltage they had when the power was turned off.  It does take a few days
however.
Bill
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