[volt-nuts] Fluke 883AB differential voltmeter

Mark Sims holrum at hotmail.com
Fri Mar 19 01:04:25 UTC 2010

I just finished restoring a Fluke 883AB differential voltmeter (and a 845AB null voltmeter).

The 883 AB needed new battery packs (I used 4 x nine AA cell nicad packs and a 4 subC cell pack)...  remarkably cheap from a Ebay vendor.  The original 9.6V packs used an unobtainium coin cell and would have cost around $200 to replace).  Also the power supply for the AC input converter was fried (transistor, zener, cap).

Final problem was it would not zero properly.  The zero circuit uses two diodes to make a +/- 0.6V supply driving the offset pot.  The unit was offset so that you could not reach zero and the offset pot had fairly little range.  Adjusting the chopper didn't help.  I replaced the diodes with three 1.2V reference chips (making a -1.2 to +2.4V supply).  This centered the zero adjustment and gave better range.

Adjusting the KVD is a pain...  you have to unsolder/solder various jumpers, etc.  Anyway,  it now seems to be working better than new.

Now to the Fluke 515A calibrators.  They have two 18 (AAA?) cell packs.   Replacements can be had for $175...  I think I can do better (or will do without).

I also have a Space Labs digital igniter tester (basically a Kelvin ohm meter).  Uses a 6 cell NiMH coin cell pack built into a piece of PVC pipe.  One place wanted $600 for the replacement!   Since the unit only draws 11 ma while you hold the test button,  I replaced it with a 9V smoke alarm battery / diode to block charging.  Should last forever (and not self discharge in a month) 		 	   		  
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