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[AMPS] Problem with SB-220 Bias Diodes

To: <amps@contesting.com>
Subject: [AMPS] Problem with SB-220 Bias Diodes
From: 2@vc.net (measures)
Date: Fri, 1 Sep 2000 14:15:15 -0700
>
>> Ä  I lost count.  --------     Please describe how you remove each type of
>> anode-cooler.  What does a ''barnacle'' look like?  Is this a common
>> occurrence?   > Cheers, Tom
>
>Barnacles are described in many texts. Copper actually grows 
>barnacles when in a vacuum.

[chortle]  these are long copper filaments that burn away easily.  Are 
3-500Z anodes made from copper?
>
>This entire topic has been discussed here before. 

?  We have heard taurine feculance here before..  

> Repeating it with 
>you will do very little good. You seem to think an ionized path 
>inside the tube will always leave an arc point marking that can be 
>easily located, and a barnacle will remain long after an arc.
>
I have opened dozens of kaput 3-500Zs from amps that reportedly had a 
big-bang.  I have yet to see a barnicle.  

>Tube faults like that are intentionally removed by controlled arcing, 
>and uncontrolled flash will do the same thing.
>
>If the tube repeatedly arcs, it needs to be replaced.   
>
>I'm more interested in your claim the grid fails to be a shield in the 
>3-500Z at 80 MHz, and the grid capacitors raise that frequency. 
>How do you determine that?
>
A dipmeter. If the grid were resonant where you claim, the amplifier 
could not oscillate at c. 110MHz.  

>If I do a plot of S12 or S21 on a cold tube in a test fixture, would 
>you like to put it on your web page and remove the incorrect data? 

If no such dips occur in a SB-220 at the frequencies you claim, the 
''incorect data'' is not mine. 

later, Tom.  


-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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