[Amps] Switching PS for filaments?

[Robert B. Bonner]

What ever happened to the simple transformer with a grounded, or B- fed
center tap?

BOB DD

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of rgroh at swbell.net
Sent: Sunday, February 18, 2007 1:23 PM
To: amps at contesting.com
Subject: Re: [Amps] Switching PS for filaments?

Ok, how about pulling all the treads together on this topic and both
summarize and visualize an ideal filament supply -
1.    Regulated DC voltage - low noise

2.    Voltage output settable to accommodate different tubes *

3.   Output current is both controlled (will take care of turn on) and
limited - current limit settable to accommodate different tubes

4.    Ability to interlock with other control circuits to, for example, ease
implementation of delaying application of HV, interlock with blower,
delaying turnoff for cooldown. 

5.    It would be neat to tie all of this plus the voltage settability* to
allow even more flexible operation such as standby operation (i.e. running
in a 'almost ready' to go on the air - filament running at lower voltage, no
HV applied, etc, low speed on fan and then, with one switch contact, be up
full and ready to go in a couple of seconds).

There has been a lot of discussion about whether or not controlling current
on start is good, whether running filaments at lower voltages will prolong
tube lifetime, etc. There is certainly debatable aspects of these factors
but probably two points would be admitted by most (if not all) of us:
1.    Controlling filament current surge on startup can't hurt
2.    Delaying HV application until filament is up to temperature and
stabilized can't hurt
3.    Having a cool down period can't hurt.

Agreed?

73
Bob, WA2CKY


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