It's not hum - the mainframe supplies regulated +75 DC for
plugin heaters. It's Coarse Balance. The beautifully simple
circuit Tek used is only possible with 8393's.
Dave Wise
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-----Original Message-----
From: TekScopes@...
[mailto:TekScopes@...] On Behalf Of Don Black
Sent: Saturday, January 21, 2012 7:55 PM
To: TekScopes@...
Subject: Re: [TekScopes] Re: Nuvistors.
Perhaps it was just easier to provide a DC heater supply of 12
volts at
half the current of a 6 volt tube in a tubes scope for hum reduction.
Don Black.
On 19-Jan-12 10:30 PM, phosphorphile wrote:
Yes, it may be a 13 volt filament is easier to run at
slightly lower voltage because perhaps the voltage being twice
and the current being half of a 6 volt filament would make for
a more constant current with line variations. Probably the way
tungsten filaments work?
The 8393 was used in early 453's and later 503's, I know.
Mebbe other models too.
