I am working to restore a vintage cobra 2000 GTL CB. The meters had stopped
working, due to being worn out. I found new meters of the same physical
size, but they do not respond full scale to the incoming signals. So I would
like to add a small voltage amp between the chassis (voltage source) and the
meter.

thanks in advance.
bob in phx

On Sun, 24 Jun 2007 15:11:03 -0700, "Bob in Phx"
wrote:

I am working to restore a vintage cobra 2000 GTL CB. The meters had stopped
working, due to being worn out. I found new meters of the same physical
size, but they do not respond full scale to the incoming signals. So I would
like to add a small voltage amp between the chassis (voltage source) and the
meter.

thanks in advance.
bob in phx


The easy way would probably be an op amp with an adjustable resistor
in the feedback to allow you to set the gain - op amp cookbook would
be a good place to look.

You want it single supply - and that may require a "rail splitter" to
create an artificial ground for the meters at some voltage greater
than zero - then you could set both the (Span) Gain and Zero for each
meter. A rail splitter is a simple voltage follower that amplifies a
voltage divider output to provide a stable "zero" reference
independent of the current.
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