[R-390] Panel meters again

[David Wise]

It was Jan Skirrow, and his mod is documented at his "Boatanchor Dreams" website, http://www.islandnet.com/~dma/Boatanchors/ .
The article is also linked from http://www.r-390a.net/faq-refs.htm .

The two mods come from different philosophies.  Jan's is "external", attaching to the existing circuit without modifying it.
The Wise/Gitzen mod is "internal", reworking the design to make it compatible.
If you are a stickler for historical accuracy, Jan's mod minimizes the touch.
If you like correcting the problem at its root, then W/G will satisfy you more.

Dave Wise
________________________________________
From: R-390 [r-390-bounces at mailman.qth.net] On Behalf Of Drew P. via R-390 [r-390 at mailman.qth.net]
Sent: Thursday, October 30, 2014 10:55 PM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] Panel meters again

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

______________________________________________________________
R-390 mailing list
Home: http://mailman.qth.net/mailman/listinfo/r-390
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:R-390 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html