[volt-nuts] Fluke 731B battery & charge circuit

Christopher Brown cbrown at woods.net
Tue Jun 18 03:30:54 EDT 2013

On 6/17/13 6:50 PM, Orin Eman wrote:
> Since it doesn't seem to much mind 11V of 'ripple', I'm tempted to stick an
> LM317L in there instead of the fussy zener/jfet/2n3904 circuit.  I just
> have to go work out how much current it's drawing so I don't overheat the
> LM317L.  I figure any slight drift from the LM317's voltage setting
> resistors isn't going to matter at all.  I might just do this to add to the
> knowledge base here.
> Orin.

If the jfet is good (sounds like it is).

Check the resisters on the PS board, IIRC it is the 510ohm one that is
the current limiter for the charging circuit.

Replace the zener...pennies

Make sure the batteries are NiCd of about the right capacity (400 -

  The charge circuit is dead simple and should float the pack at 40 - 60ma.

>From you description it just sounds like the zener voltage is low, just
like both of mine.

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