What I looked at in the schematic didn't make one lick of sense to put a
cathode choke to ground on a grid driven amp, then place a shunt resistor
across the choke (especially that high of value). The resistor wouldn't serve
any purpose unless the choke opened. And if it did, you'd really be better off
not to have the resistor so the tube would not conduct at all. Also, the choke
isn't needed as there's NO RF there to block from ground. He also put a RF
choke across the attenuator resistor going to the control grid. That don't make
sense to me. I would think you would use two non-inductive resistors (Rich will
jump me for calling them that). He also has a choke in series with one of the
attenuators resistors going to ground which would raise the inpedance there
too. All I've ever seen here, for an attenuator, is a couple of non-inductive
resistors. Why put a choke in series with the screen lead? All that's needed is
a bypass cap at the tube socket pin. Here, the cap is on the
other side of the choke where it's shouldn't be. Last, there's a 0.001 bypass
cap hooked right from the control grid to ground on the wrong side of the RF
blocking choke. The RF will go to ground and not to the tube! Am I missing
something about this?
Best,
Will
*********** REPLY SEPARATOR ***********
On 1/30/06 at 2:53 PM R.Measures wrote:
>On Jan 30, 2006, at 9:44 AM, Gary Schafer wrote:
>
>> Don't believe everything you see on the internet.
>>
>
>Amen, Gary.
> Tim McVeigh bombed the Murrow Bldg. because of false info he read on a
>Web site.
>
>> 73
>> Gary K4FMX
>>
>>> -----Original Message-----
>>> From: amps-bounces@contesting.com
>>> [mailto:amps-bounces@contesting.com] On
>>> Behalf Of Partain, Chuck
>>> Sent: Monday, January 30, 2006 11:14 AM
>>> To: Bill Turner; amps@contesting.com
>>> Subject: Re: [Amps] cathode to ground in tetrode amp
>>>
>>> ya
>>>
>>>
>>>
>>> <http://www.angelfire.com/nb/ni4l/gu84b.html>
>>> http://www.angelfire.com/nb/ni4l/gu84b.html
>>>
>>> Look down at the ONE tube schematic.
>>>
>>> This is the only one I have seen for HF so far that's not too
>>> convoluted.
>>>
>>>
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Bill Turner [mailto:dezrat1242@ispwest.com]
>>> Sent: Monday, January 30, 2006 11:11 AM
>>> To: Partain, Chuck; amps@contesting.com
>>> Subject: Re: [Amps] cathode to ground in tetrode amp
>>>
>>>
>>> ORIGINAL MESSAGE:
>>>
>>> At 07:14 AM 1/30/2006, Partain, Chuck wrote:
>>>
>>>
>>>
>>> OK, getting into this more and more every day and learning. Looking at
>>> some designs on this GU-84b
>>> amp, I see a lot if not most of the cathodes have resistance, some a
>>> lot(30k) some little (.7) to ground.
>>> The screen grid and control grids are not grounded and have
>>> respectively
>>> ~350 and -150v on them.
>>>
>>> Why wouldn't it just essentially go to ground? what does the R do in
>>> series?
>>>
>>> thanks as always.
>>>
>>> KA1MWP
>>>
>>>
>>>
>>>
>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> Is there a schematic we could look at?
>>>
>>> 73, Bill W6WRT
>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>
>Richard L. Measures, AG6K, 805.386.3734. www.somis.org
>
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