You are right about the 'not a directly heated cathode'. I've not detected
any hum
what-so-ever in this amp with the B- setup I have. If I used a standard CT
filament
transformer for B- the hum would be there. When time allows, I will hook
the scope up and double check the amp.
Regards,
Larry N5BIP
-----Original Message-----
From: W6RU@aol.com [mailto:W6RU@aol.com]
Sent: Thursday, September 08, 2005 9:25 PM
To: lncarman@swbell.net; amps@contesting.com
Cc: k7rdx@charter.net
Subject: Re: [Amps] YC-156 Triode
In a message dated 9/8/2005 5:56:31 P.M. Pacific Daylight Time,
lncarman@swbell.net writes:
My filament transformer didn't have a center-tap
so I improvised a B- by using an artificial centertap made of diodes
connected
to each leg of the filament's secondary.
This tube is NOT a directly heated cathode. It has a indirectly heated
cathode ... connection to the cathode is the outside heater connection. This
is where you connect the B- through a RF choke to the tube. I found that any
other B- connection to this tube will induce hum in the transmitted signal
do to the AC heater current ending up in series with the cathode B-.
Terry W6RU
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