[Heathkit] SB-200 Question

[Carl]

The coil can vary depending on the self parasitic frequency of the tube. 
This can vary from around 70-150 mHz for the usual glass tubes and higher 
for the ceramic-metal versions.

The coil is there to be resonant at the parasitic and the resistor is there 
to prevent it by "suppressing" it from starting. The resistor does not 
absorb parasitic power but can get hot on 10M if the coil is resonant too 
low. The tube is the determining factor but sloppy construction can 
aggravate the severity.

If the tube for the HB amp has a recommended coil in a construction article 
then use it. If not 3-4T of #14 roughly 3/8" ID and spread to resonate is 
generally used up into the 3CX800 power region.

With the suggested 5W resistor the caps work with any coil; Ive not tried 
different resistors but have used the method for 572B, 4-400A, 3-500, 813, 
3CX800 and even 250TH's. Trying to find NOS 33-51 Ohm 2W carbon comps that 
havent radically changed value is becoming a chore unless you have a stash 
of Allen Bradley.

Carl
KM1H


----- Original Message ----- 
From: "Donald Spoon" <drspoon at sbcglobal.net>
To: "Heathkit" <heathkit at mailman.qth.net>
Sent: Sunday, February 28, 2010 5:57 PM
Subject: Re: [Heathkit] SB-200 Question


>I wasn't watching the EMail  addy and this didn't go to the right place,
> so here goes again.
>
> This raises a more "generic" question that I have been meaning to ask
> the Elmers/Engineers/Wizards that hang out here.  Is there a rule of
> thumb in making  these parasitic chokes, or are they specific for each
> tube and/or circuit?  Can I use Carl's circuit with 3 turns of wire in a
> home-brew linear and be assured that I am reasonably close?
>
> -Don Spoon-
> K0APK
>
> Ronnie Hull wrote:
>> Gentleman
>> I need to build up two parasitic suppressors for the 572's in the
>> sb200 I'm restoring.
>>
>> heathkit p/n 45-53
>>
>> I know this is a resistor wound with copper wire. WHAT value
>> resistor,  what size wire and how many turns
>>
>> Can anyone help me with this?
>>
>> Thanks in advance
>>
>> Ronnie
>>
>>
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