[AMRadio] VTVM Battery Eliminator

Grant Youngman nq5t at comcast.net
Thu Jul 20 21:13:42 EDT 2006

> The thing about batteries is they give great isolation.  A 
> VTVM uses a differential amplifier for the metering.  It may 
> be a problem getting another supply in place with the 
> isolation that is needed.  

There was some discussion regarding this topic on the Tempe Heathkit
reflector in the 10/04 timeframe.  At lest on the Heath VTVM, there is
apparently an issue wrt current draw from the power transformer, regardless
of how simple or complex one chosses to go with the idea of feeding a 1.5v
DC supply to replace the battery.  I've kept a battery going in my v-7A
since 1957.  I had a bit of corrosion once, many years ago, but cleaned it
up -- and have checked it once a year or so since, with no more problems.


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