Trevor Wilson scribbled thus:

On 20/03/2014 3:16 PM, wrote:
I found this circuit somewhere, (I can't remember) to replace the
1.50 volt battery in a VTVM. I have an RCA WV98C Senior Voltohmyst
VTVM that is in perfect condition but doesn't get used very often.
This battery retrofit circuit takes power from the 6.30 volt filament
transformer and is built around an LM317. With a trim pot you set it
for 1.55 volts and you never have to change a battery again. It also
needs to occupy an area no larger than the battery presently does.

As much as I like keeping things original, I'm worried that the
battery is going to leak and rot the inside of the unit. I was going
to build the circuit but it occurred to me that I should probably be
concerned about the current that the LM317 will be dissipating when
the meter is used on the low ohms range. Does anyone have a feel for
the size that an adequate sized heat sink should be in order to
handle this? Thanks, Lenny


**Crazy idea, Lenny:

Move yourself into the 1970s and buy yourself a digital multimeter.
Most of them operate on a 9 Volt battery. Replace the battery every
year and you'll be sweet. Even a US$20.00 meter will give you a vast
improvement in every performance parameter over your ancient POS,
which is likely well outside it's original performance specs.


Like this one:


http://au.mouser.com/ProductDetail/E...qaRLKRQ5wis%3d

One of my meters measures the usual Volts, Amps & Ohms AND light
intensity, sound pressure level, relative humidity and transistor
gain. I recall that it cost me AUS$50.00.

I have a nice collection of analogue meters (I recently acquired a
beautiful AVO 8 Mk7), but I never use them anymore.

Go digital. You will not be sorry.


There is no way that I will give up using my AVO8...

--
Best Regards:
Baron.