[R-390] Panel meters again

[Barry]

Sorry about the all-caps SOMEWHERE.  I didn't intend that.
Barry

Sent from my iPad

> On Oct 31, 2014, at 6:20 AM, Barry <n4buq at knology.net> wrote:
> 
> I believe it was Jan Skirrow who published the op-amp scheme.  His pages may still be out on the interwebs SOMEWHERE.
> 
> Barry - N4BUQ
> 
> Sent from my iPad
> 
>> On Oct 31, 2014, at 12:55 AM, "Drew P. via R-390" <r-390 at mailman.qth.net> wrote:
>> 
>> Tisha wrote:
>> [snipped]
>> 
>> "... if you know the internal resistance of the existing panel meter you could
>> make a little circuit that has the same shunt resistance, tap either side
>> of a resistor in series and run that into an op-amp, zero and span that to
>> your hearts content and drive a different meter. (even, Gasp! a digital
>> meter <joke>). Add a little bit of capacitance to the op-amp circuit, make
>> the thing smooth out the values, etc...
>> 
>> You could steal power from the 6.3 VAC filament supply, run it to a little
>> rectifier/regulator and mount that on the same board. Maybe even add a
>> little internal meter LED light. (or a red flashy LED in the corner to show
>> on peaks, that would be neat)."
>> 
>> [snipped]
>> 
>> "Thinking of a DIP-8 Op-amp package, three lead regulator, tiny little
>> bridge rectifier, a few resistors and caps, two small pots for scaling,
>> yea, that would be neat. It could be mounted on a breadboard the size of a
>> 50 cent piece."
>> 
>> Someone here did just that some years ago...might check the "Pearls of Wisdom".  IIRC, it was Les Locklear. My preference goes for Dave Wise's modification, not as versatile, but certainly much less work.
>> 
>> Drew
>> 
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