¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. TekScopes
  2. Messages
Single Messages Topics Expanded Polls

Re: Tube test adaptor for Tektroinx 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals

 

A center tapped filament transformer, or a 'hum balance' circuit to create an artificial center tap will do even better. That circuit was often no more than a 200 ohm pot across the winding, with the wiper connected to ground, and both filament leads floating above ground. A 2W pot was common for this use.


Michael A. Terrell

-----Original Message-----
From: Mike Dinolfo <mdinolfo@...>
Sent: Dec 5, 2018 10:53 PM
To: [email protected]
Subject: Re: Tube test adapter for Tektronix 575 was: Re: [TekScopes] FS: miscellaneous Tektronix manuals

Another thing to consider (if you are feeding tube filaments via AC
power) and want to minimize hum is to use twisted pair wiring to
distribute AC power to the tube filament socket connections (rather than
individual single conductor wires which are haphazardly separated from
each other). Twisted pair tends to minimize inductive (magnetic)
radiation within the equipment/chassis that could otherwise occur with
separated wires supplying AC to the tube socket filament pins; the
magnetic field (at 60 hz) can lead to audio hum. Of course, it's also
OK to use single conductor wires which are twisted together in "paired"
wiring for the filament power distribution.

Mike Dinolfo N4MWP
Join [email protected] to automatically receive all group messages.