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) _________________________________________________________________ Hotmail: Trusted email with powerful SPAM protection. http://clk.atdmt.com/GBL/go/210850553/direct/01/

I also recently restored a Fluke 845AB Null Detector. I used cheap Nickel Metal Hydride batteries to replace the originals, but I was tempted by the improving capacities of Low Self Discharge NiMH batteries: http://en.wikipedia.org/wiki/Low_self-discharge_NiMH_battery The repair seemed to work very well, but a fault quickly developed: when switched to 'LINE OPR' (mains powered) the meter swings to the extremes and then settles to zero and won't move again as though it's switched off. I'm too busy to deal with that right now, but I was wondering, how much noise should I expect to see in the meter needle with the input shorted? Alan ----- Original Message ----- From: "Mark Sims" <holrum@hotmail.com> To: <volt-nuts@febo.com> Sent: Friday, March 19, 2010 1:04 AM Subject: [volt-nuts] Fluke 883AB differential voltmeter > > 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) > _________________________________________________________________ > Hotmail: Trusted email with powerful SPAM protection. > http://clk.atdmt.com/GBL/go/210850553/direct/01/ > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

Hi Alan: If the factory battery was Ni-Cad it's a mistake to replace it with Ni-MH. During charging they are very different and the Ni-MH might overheat. Is there a temperature sensor as part of the charging electronics? Have Fun, Brooke Clarke http://www.PRC68.com Alan Scrimgeour wrote: > I also recently restored a Fluke 845AB Null Detector. I used cheap > Nickel Metal Hydride batteries to replace the originals, but I was > tempted by the improving capacities of Low Self Discharge NiMH batteries: > http://en.wikipedia.org/wiki/Low_self-discharge_NiMH_battery > > The repair seemed to work very well, but a fault quickly developed: > when switched to 'LINE OPR' (mains powered) the meter swings to the > extremes and then settles to zero and won't move again as though it's > switched off. I'm too busy to deal with that right now, but I was > wondering, how much noise should I expect to see in the meter needle > with the input shorted? > > Alan > > > ----- Original Message ----- From: "Mark Sims" <holrum@hotmail.com> > To: <volt-nuts@febo.com> > Sent: Friday, March 19, 2010 1:04 AM > Subject: [volt-nuts] Fluke 883AB differential voltmeter > > >> >> 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) >> _________________________________________________________________ >> Hotmail: Trusted email with powerful SPAM protection. >> http://clk.atdmt.com/GBL/go/210850553/direct/01/ >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. > > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > >

I didn't check the detail because the manual warns not to charge for more than a week, so I assumed it was just on the high side of a trickle charge and so ok for NiMH too. Alan ----- Original Message ----- From: "Brooke Clarke" <brooke@pacific.net> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Friday, March 19, 2010 4:43 PM Subject: Re: [volt-nuts] Fluke 883AB differential voltmeter > Hi Alan: > > If the factory battery was Ni-Cad it's a mistake to replace it with Ni-MH. > During charging they are very different and the Ni-MH might overheat. Is > there a temperature sensor as part of the charging electronics? > > Have Fun, > > Brooke Clarke > http://www.PRC68.com > > > Alan Scrimgeour wrote: >> I also recently restored a Fluke 845AB Null Detector. I used cheap >> Nickel Metal Hydride batteries to replace the originals, but I was >> tempted by the improving capacities of Low Self Discharge NiMH batteries: >> http://en.wikipedia.org/wiki/Low_self-discharge_NiMH_battery >> >> The repair seemed to work very well, but a fault quickly developed: when >> switched to 'LINE OPR' (mains powered) the meter swings to the extremes >> and then settles to zero and won't move again as though it's switched >> off. I'm too busy to deal with that right now, but I was wondering, how >> much noise should I expect to see in the meter needle with the input >> shorted? >> >> Alan >> >> >> ----- Original Message ----- From: "Mark Sims" <holrum@hotmail.com> >> To: <volt-nuts@febo.com> >> Sent: Friday, March 19, 2010 1:04 AM >> Subject: [volt-nuts] Fluke 883AB differential voltmeter >> >> >>> >>> 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) >>> _________________________________________________________________ >>> Hotmail: Trusted email with powerful SPAM protection. >>> http://clk.atdmt.com/GBL/go/210850553/direct/01/ >>> _______________________________________________ >>> volt-nuts mailing list -- volt-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >>> and follow the instructions there. >> >> >> >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. >> >> > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.