USM-223 Military Multimeter - Batteries??

[Mike Dinolfo]

Larry Wolken wrote:
>
> Howdy Gang --
>
> I come to ask help from the collective experience of the boatanchor boys.
> Recently picked up one of the classic large meter military handheld
> multimeters in good shape complete with cover.  It appears to have contain
> FET's among other components  on two PC boards.  The volt and amp ranges
> work fine, but when I put batteries in it, and select the ohm ranges, the
> needle stays pinned, regardless of the pot adjustment.
>
> The label on the back of the case says that it's been internally modified
> to accept two alkaline batteries in place of six mercury cells.  There are
> three battery slots which nicely hold two AA's and one C cell.  Are these
> likely to be the right batteries or no??

Ah, maybe, or maybe not.  I say maybe because I also have a USM-223; my
unit does _not_ have any indication of the battery type having been
changed at the factory or elsewhere.  However, my unit has 3 batteries,
like yours; one of the batteries is a type C, but the other two
batteries are "odd-ball" units, each 4.5 volts alkaline, approximately
the same size as AA size.  I had to buy replacements a few years ago;
they were not cheap, as I recall (about 4 bucks each), and not all that
easy to find (the batteries which I found were Energizer #523).  You
might have a similar situation with your meter.

I might be able to find a schematic for my meter; if you need a copy,
let me know by private email and I'll send you a copy by snailmail.

Mike Dinolfo N4MWP

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