[R-390] Line Level meter

[ka9egw at britewerkz.com]

OK, I found a pcb for six bucks which runs off a single positive rail supply
[which I can tap from the filament or pilot lamp circuit] and uses a single
TL071 op-amp and a handful of diodes and resistors, and presents a line load
of aboout 100K or better.  Total board size looks be about an inch and a
half square.  The complete kit is about twenty bucks.  Still cheaper than
trying to source an original meter.  It's doable.

73, Brian KA9EGW

-----Original Message-----
From: r-390-bounces at mailman.qth.net
[mailto:r-390-bounces at mailman.qth.net]On Behalf Of William A Kulze
Sent: Wednesday, August 25, 2010 8:37 AM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] Line Level meter


For what it's worth, some years ago I stumbled upon an old VU meter from
some other application and it worked just fine as a direct replacement. I
didn't do any measurements, but it seemed to do just fine.

Bill W2NVD


Having solved the mystery of the 3rd wire...one of my sub-projects is
figuring out the dropping resistor to use with a physically-correct 1mA
meter movement [matches the 390 meters but it's just a 1mA DC meter, no
internal rectifier/cap like a true VU meter] and a bridge rectifier to make
a Line Level VU meter .

Thanks,
Brian KA9EGW

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