[AMRadio] Metering circuits

John Coleman, ARS WA5BXO wa5bxo at pctechref.com
Sun Jan 2 19:06:59 EST 2005

Very good point Don

John, WA5BXO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Donald Chester
Sent: Sunday, January 02, 2005 6:04 PM
To: amradio at mailman.qth.net
Subject: [AMRadio] Metering circuits

One word of caution.  If you use the above circuit with directly heated 
cathode tubes, be very careful to avoid shorting either side of the
line to ground.  I lost a plate meter when I accidentally clip-leaded
side of the filament (I had intended it to be the xfmr ct) to ground,
running some tests.  Half the filament voltage, in my case 5.75 volts, 
appeared directly across the DC millammeter terminals.  It didn't
burn out the coil in the meter before I realised the mistake and 
disconnected it, but by then it had literally shaken apart the movement.


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