[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
filament 
line to ground.  I lost a plate meter when I accidentally clip-leaded
one 
side of the filament (I had intended it to be the xfmr ct) to ground,
while 
running some tests.  Half the filament voltage, in my case 5.75 volts, 
appeared directly across the DC millammeter terminals.  It didn't
actually 
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.

Don K4KYV


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