[Hallicrafters] SX-71 question

[Carl]

National also reduced the voltage on the 6H6 and later the 6AL5, they used 
4.3 Ohms. Dont know who came first as the SX-71 and HRO-50 both came out in 
1949 but the SX-71 had 4 prodution runs ending in 1954 so was the resistor 
in all of them?

Its interesting to note that altho the Radiotron Designers Handbook 4th 
Edition of 1952 discusses the hum issue and methods to minimize it does not 
mention the filament resistor.

Carl
KM1H



----- Original Message ----- 
From: "Asif Khan" <hallicraftersx28 at aol.com>
To: <Hallicrafters at mailman.qth.net>
Sent: Thursday, December 09, 2010 4:37 AM
Subject: Re: [Hallicrafters] SX-71 question


>
> In the absence of the resistor an objectionable  60 hz hum would appear in 
> the audio.The resistor reduces the AC filament  voltage to the ANL tube 
> thereby also reducing the AC hum .
> Nick
>
>
>
>
>
>
>
> -----Original Message-----
> From: Art Lebermann <artleb at earthlink.net>
> To: Hallicrafters <Hallicrafters at mailman.qth.net>
> Sent: Thu, Dec 9, 2010 1:32 am
> Subject: [Hallicrafters] SX-71 question
>
>
>
> he SX-71 schematic shows a 6.8 ohm resistor in the filament connections to 
> V11
> 6H6 - AVC/ANL) and V12 (6AL5 - FM detector).  Does anyone know the reason 
> for
> educing the filament voltage to these tubes?
> 73,
> RT
> 6REQ
> ______________________________________________________________
> allicrafters mailing list
> ome: http://mailman.qth.net/mailman/listinfo/hallicrafters
> elp: http://mailman.qth.net/mmfaq.htm
> ost: mailto:Hallicrafters at mailman.qth.net
> List Administrator: Duane Fischer, W8DBF
> * For Assistance: dfischer at usol.com **
>
> his list hosted by: http://www.qsl.net
> lease help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> Hallicrafters mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hallicrafters
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Hallicrafters at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html