[volt-nuts] Fluke 5100B Calibrator

J. L. Trantham jltran at att.net
Sun Sep 2 11:58:20 UTC 2012


Thanks for the reply.

There were two tantalums on the HV board that were, literally, exploded.
Just an empty shell.  I could see no other obvious issues except one of the
power transistors on the A17A1 boards was 'loose', one mounting screw not
screwed in all the way and the other 'tight' but with crossed threads.  I
replaced the two obvious tantalum problems, properly installed the power
transistor and all power supplies came up except the -15 VDC, sitting around
- 0.5 VDC.  I found the -15 VDC regulator very hot, two series 6.8 V zeners
used to drop the -40 VDC unreg to about -26 VDC before it got to the LM7915
were shorted and the resistance on the -15 VDC buss at about 0.5 ohm to

I didn't have any 6.8 V zeners so I installed three 5.1 V zeners and started
lifting cards.  The resistance on the -15 VDC buss went to about 600 ohms by
lifting the DAC board.  Found a shorted tantalum with no obvious external
damage, fired it up and, again, the -15 VDC buss would not come up.  Again,
about 0.5 ohm to ground and this time the shorted tantalum was on the Analog
Control board.  Replaced it and now, it all seems OK.

The three 'new' zeners and LM7915 all seemed to survive the 'new' shorted
tantalum without a problem though they were, again, quite hot when I removed
the A9 Power Supply Regulator Board.

My A9 board is different from the schematic in the manual.  My board uses an
LM7915 with two 6.8 V zeners in series to the - 40 VDC input to supply - 15
VDC where the schematic and parts list show a LM7905 with a 10 V zener in
the ground lead and a single 6.8 V zener in line with -40 VDC supply.  

I think I have seen three different part numbers for manuals.  I ordered one
from theBay that is not here yet.  Any other sources of manuals on the net
that you know of?  I would like to find one (or at least the 'change
sheets') that apply to my serial number.

I had read about the 5102B, a 5100B (or is it a 5101B) that comes in a
'case' and is designed for any/all position operation, not just sitting
upright.  I didn't know about the 'pre-flight' upright position time
requirement on the 5100B.  It looks like I got away with it this time

Thanks again for your reply and help.


-----Original Message-----
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
Behalf Of Pete Lancashire
Sent: Saturday, September 01, 2012 10:46 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Fluke 5100B Calibrator

I would now go after all the tants. They have the bad habit of doing the
power supply in.

Another warning, never power the unit up if it has not been bottom down for
at least a couple hours. The wonderful world of Hg wetted relays.

On Sat, Sep 1, 2012 at 7:25 PM, J. L. Trantham <jltran at att.net> wrote:
> In an effort to get a 'standard' for DC and AC voltage and current, 
> along with resistance, I recently acquired a Fluke 5100B.
> After an effort, finding several dead/shorted/blown (literally) 
> tantalum capacitors as well as shorted zeners and loose mounting 
> screws for the HV output section transistors, it seems to be working 
> on all ranges.  It has the wideband frequency option (03) and the HPIB 
> option (05) but I have not had a chance to try those out yet.
> Anyone on the list with any experience with this unit?  Any hints, 
> suggestions, pitfalls I need to know about?
> I downloaded the manual from the Fluke site.
> My plan is to use it along with an Agilent calibrated 3458A to be able 
> to calibrate other DMM's.
> Any suggestions appreciated.
> Thanks in advance.
> Joe
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