Re: [volt-nuts] fluke 731b battery pack

[Christopher Brown]

If even with a fully charged pack the batt charge side gets high enough
to feed into the ref you need to check the current value of the current
limiting resistor in the charge circuit.

Don't have the exact details in my head at the moment (was about 3 years
ago) but in both of my 731Bs that resistor had dropped in value by more
than a little and was floating the batteries at a higher voltage.  I
replaced with a correct value over-rated metal film type and no more
issue, max floating voltage for ~ C/20 maint to the pack is below cutoff.

If it is climbing high enough compared to the other feed, then resistors
have drifted and the batt circuit is running to hot or the filter AC ->
ref supply is running too low.

On 8/3/16 13:30, Orin Eman wrote:
> On Wed, Aug 3, 2016 at 2:08 PM, David  wrote:
> 
>>
>> I looked at the schematic and is seems feasible without excessive
>> effort.  Either the existing simple series preregulator can be
>> modified or replaced allowing it to both charge the battery (through a
>> blocking diode) and power the instrument or a completely separate
>> power charging circuit can be added in parallel.
>>
> 
> 
> The existing charging circuit _is_ in parallel with the pre-regulator; they
> are separated by CR5 and CR6 and the pre-regulator/battery outputs are
> combined by CR8 and CR9.  The only problem with the existing circuit is
> with a fresh, strong, fully charged battery pack, charging pulses will leak
> past CR8 with only R1/C1 to filter them.
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Re: [volt-nuts] Fluke Diff's

[Christopher Brown]

845A
845AB

845AR


On 11/20/13 6:58 AM, Pete Lancashire wrote:
 I'm working on a list/table of the Fluke 800/900 solid state
 differentials.
 
 Will be putting on a public web page when close to being
 done.
 
 If anyone can help fill in the 'blanks' or add comments I would
 greatly appreciate it.
 
 Thanks
 
 -pete
 
 Data so far
 
 871A
DC 3+dial
 
Have seen with 801 10KV divider 1K:1 10K:1
 
 883A
DC 4+dial
 
 883AB
AC/DC  4+dial
 
http://helmut-singer.de/pdf/fluke883ab.pdf
 
Basic dc voltage accuracy is 0.01% of indicated value + 5 µV. Resolution
 is 1 µV.
 
 885A
 
 885AB
DC4+dial
 
DC Differential Voltmeter achieved an absolute accuracy of 25 parts per
 million of
input +1 ppm of range +5 microvolts from 0 to 1100 VDC.
 
 887A
   DC/AC  4+dial
 
   http://www.teknetelectronics.com/DataSheet/Fluke/Fluke_887A41504.pdf
 
   http://bama.edebris.com/download/fluke/887a/FLUKE_887A.pdf
 
   Basic DC voltage accuracy is 0.005% of indicated value. Resolution is 1
 µV.
 
 887AB
   DC/AC  4+dial
 
   http://assets.fluke.com/manuals/887A_887imeng0200.pdf
 
   Artek
 
 891A
DC 3+dial
 
 893A
AC/DC  3+dial  01-Battery 02-Recorder two diff case styles
 
http://assets.fluke.com/manuals/893A_AR_imeng.pdf
 
AC and DC with 1uV Resolution, accuracy is +/-0.01% (DC) and +/-0.05%
 (DC), 50Hz to 10kHz.
 
Artek
 
893AP ?
 
893AR 893A in a 'flat' 2 RU ? Rack
 
 895A
DC 4+dial
 
 931A
RMS3+dial
 
Opt 01 Battery Pack
0pt 02 Probe Input
Opt 03 01+02
 
http://www.teknetelectronics.com/DataSheet/FLUKE/FLUKE_931B114917.pdf
 
 
 http://www.artisantg.com/info/PDF__466C756B655F393331425F446174617368656574.pdf
 
 
 335D DC Voltage Standard Diff Voltmeter
 
http://assets.fluke.com/manuals/335dimeng0100.pdf
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[volt-nuts] Fluke 845AB / 845AR neon bulb xref

[Christopher Brown]

So, working on a couple of 845s.

The AR is a franken unit assembled from the parts of 2 damaged units.

Works well, but intermittently, both neons are very weak.

The AB was working well after cleaning up the leaking battery mess, and
recapping but one of the bulbs failed.


Looking at the original manual and a 1990 update I get

NE-2U

AND

Lamp, NEON, 105-125V, 0.7MA, Wire Leads A9A-1


Cannot seem to find direct or xref


Mouser show a Chicago Miniature A9A but no A9A-1 and A9A is 65VAC/90VDC


NE-2U seems to cross to A3C, but cannot find A3C and A3C specs seem to
indicate 1.9ma


Can anyone help with the correct spec, xref to current part and supplier?

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Re: [volt-nuts] HP 419 (WAS: Fluke 335A versus HP 740B)

[Christopher Brown]

On 12/16/12 2:34 PM, Charles P. Steinmetz wrote:
 Christopher wrote:
 
 The oldest has a oval 3 pin AC connector.
 A newer one has a standard IEC socket.
 Both of these have 3 battery packs made of some form of coin cell, NiCd,
 225ma, 5 to a stack.
 
 These are what I'm familiar with (I presume you mean 4 packs, not 
 3?).  The batteries are Y-5201, long obsolete.

Yes, 4 not three.

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Re: [volt-nuts] Fluke 335A versus HP 740B

[Christopher Brown]

On 12/15/12 1:28 AM, Charles P. Steinmetz wrote:
 
 The main problem today with the HP is that it uses impossible-to-find 
 batteries.  Not only are the original batteries unobtainable, I have 
 yet to find a satisfactory replacement strategy.  It also does not 
 have a +/- 1 uV range, although I do not count that as a major fault 
 since thermocouple noise in the measurement setup frequently prevents 
 taking full advantage of the 1 uV range.

Not a 419A expert by any means, but I happen to have 3 I picked up at
parts prices and am repairing the newest of them.


The oldest has a oval 3 pin AC connector.

A newer one has a standard IEC socket.

Both of these have 3 battery packs made of some form of coin cell, NiCd,
225ma, 5 to a stack.

I found some 60ma similar cells in current production (at least in
china), but the right stuff has been impossible to find.


The newest 419 is different.  Different battery holder, and uses 4 packs
of 5 1/3AA cells.  These are not common, but are not that hard to get.

I also found ref in one of the manual change sheets about a different
battery holder.


Now, converting an older unit would not be hard.  The only thing diff is
the mount and the packs themselves.

Take a couple pieces of say 1/2in thick delrin, cut to about 2x4
(measure the space).  These mount to the same screw holes as the
original clamp mount.  Cross drill 4 holes for the packs, and stretch a
couple 0-rings around the packs once in.  This is what the newer
mount/pack from the factory is like...  Two flat plates with 4 cross holes.



Anyway, the older coin cell 419s are pretty badly damaged due to leakage
from the packs, am tearing them down for parts.  The newer one didn't
leak, am just shopping for 20 good tabbed 1/3AA cells.  Solder 5, inline
shrinktube, repeat 4 more times and done.

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[volt-nuts] Fluke 731B power switch replacement: TE Connectivity / Alcoswitch MTL206N

[Christopher Brown]

Original was MSTL206N, count not cross-ref the maker.

TE MTL206N is an exact match drop-in, same locking toggle with same
shape/size everything.

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Re: [volt-nuts] Fluke 731B parts xref

[Christopher Brown]

On 11/21/12 6:44 PM, WB6BNQ wrote:
 Hi Chris,
 
 Do you mean the Fluke 750A ?  It has connections for standard cells.  The 752 
 is a ratio
 device designed to be used with a 10 volt reference standard.  No need for 
 the 1.xx outputs
 from the 731B or the use of standard cells..

Your are correct, not the 752 (would like a 752 and a 720) but do have 2
750A.

 
 The 750A standard cell arrangement can be bypassed and set up for use with 
 just a 10 volt
 reference using the original banana jacks for the reference and null meter as 
 normal.  All
 that is needed is to (non destructively) remove one connection and add one 
 wire.
 
 BillWB6BNQ

That sounds like a very worthwhile mod.  How is it done and how does it
change operation?


As far as the 731B(s), I have 2.

One is in good working order and overall great shape.  Came out of a
standards lab in the czech republic that recently switched to a 732A.

Have a replacement NiCd pack currently cycling.  Other than cleaning,
and replacing the dead pack the only changes planned are replacing the
IEC socket with a small filtered socket (have a box of them) and
replacing R30 (if needed) to adjust the float current for the new pack
(old is 450mah, new is 2100mah.


For the second (received this morning), intend to do the same, and
repair.  I may just hard-wire around the failed switch, but beyond that,
not fixing it would just bug me.

The ref board is in good shape and does not appear to have been messed
with.  The main issues being the pot and the P/S section.


Near as I can tell the Fairchild 1N5248B is a good match for CR1, and
for 2 cents each I can just grab a batch and select.


I have a bunch of 4148 and 1n914 fairchild parts around here somewhere,
curious as to suggestion of 4448 over 4148?  Looks like 2pf v.s. 4pf and
the 4148 may start conducting a few hundred mv earlier from the datasheet.

Thanks
Chris - WL7CLA

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