[Amps] Equalizing Restistors

Richard 2@mail.vcnet.com
Sat, 2 Mar 2002 20:55:36 -0800


>Richard,
>If I understand you, I can remove the swinging choke leaving just the 25mfd 
>cap as the hv filter. 

Yes.

>If the high voltage then rises to about 3kv instead 
>of the normal 2.2 kv, I would have to change the screen voltage and the 
>grid voltage proportionally to maintain the proper operation of the 2 
>4-400's. Is this a correct assumption?

Sort of.  The proper screen potential is c.800v for AB1.  Grid bias 
should be adjusted for c.75mA of ZSAC.   This will be c. 120vdc.   
Screen V is can be obtained from a zener-string.  Since the screen 
current required for two tubes is c. 26mA, 35mA of zener bias would be 
enough.  Thus, 33v, 5w (rated @25C case) zeners will do the job.  Thus, 
one needs 25 of such zeners in series mounted on a perfboard with some 
air flowing.  One means of zener bias current is the anode supply.  
Roughly 60 - 70 ks @ 75w is indicated. 

>BTW....I understand that the 4-400's would run better with 3kv
>
Indeed.  With the tetrode config., 4000v is even better.  For SSB. some 
guys use 4800v.  In AB2-GG, 3500v is good.  

>Thanks in advance,
 
ur welcome, Bill.  have fun.  
>
>At 09:07 AM 3/2/02 -0800, you wrote:
>
>
>> >Thanks for the replies folks. I should have figured the power rating of the
>> >resistors myself......i use ohms law, must have been a "senior moment"!!!
>> >As for the swinging choke input filter, Im stuck with it unless I
>> >completely re-do the whole Thunderbolt. If I go to a capacitor in put
>> >filter, the HV will rise and this will cause all sorts of headaches I
>> >think.
>>
>>  Switching to C-input and removing the swinging-choke should raise the
>>anode-V to about 3kVDC, which is c. the same as a SB-220 and TL-922.  My
>>guess is that the extant tank components will withstand the increase.
>>
>> >My main reason for changing the hv cap is to increase the
>> >capacitance from the stock capacitance of 8mfd to about 25mfd to help the
>> >regulation on ssb.
>>
>>  To compensate for the transient unregulation produced by rapidly
>>changing current on SSB/CW through the swinging choke, it might take
>>considerably more C.  I would start off with c. 0.1F and check it with a
>>DC 'scope.
>>
>>
>> >Any other suggestions will be greatly appreciated.
>> >
>> >
>> >
>> >Bill Russell
>> >KC2IFR
>> >
>> >_______________________________________________
>> >Amps mailing list
>> >Amps@contesting.com
>> >http://lists.contesting.com/mailman/listinfo/amps
>> >
>>
>>
>>-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
>>www.vcnet.com/measures.
>>end
>
>Bill Russell
>
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>


-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
end