>Subject: Re: [AMPS] Parasitics and Blown Filaments
>Sent: 5/7/97 2:44 PM
>Received: 5/9/97 7:09 AM
>From: Phil Clements, philk5pc@connect.net
>To: km1h@juno.com
>CC: amps@contesting.com
>
>At 02:38 PM 5/7/97 EDT, you wrote:
>>Hi gang...
>>
>>I actually read Tom's response and laughed so hard that I accidentally
>>deleted his message.
>
>>Blown filaments are absolutely possible due to an internal tube failure.
>>Consider the failure a parasitic, gas, lousy assembly, etc. Any one of
>>those can do it.
>
>Far more filaments have been blown from the above than with inrush current.
>
>
>>A case in point is the huge number of Svetlana 572B's with blown filament
>>failures....I had a least 2 dozen happen to me and my customers. Put them
>>in a known stable amp such as a SB-200, turn it on and everything looked
>>fine. Key the relay with NO DRIVE and "Bang". Svetlana has acknowledged
>>the stability problem and has redesigned the tube. It was an acknowledged
>>parasitic problem based upon internal geometry, not gas or poor
>>construction.
>>
>>I feel that Tom's response is irresponsible and is strictly a
>>MFJ/Ameritron CYA smoke screen.
Not Invented Here Syndrome.
>More than one of us would like to know a description of the parasitic
>suppressors installed on the AL-811 amp!
They are essentially the same design that Mr. Rauch submitted to N7WS
during the VHF parasitics debate. Ls is made from copper buswire. At
100MHz, the Rp (parallel equivalent VHF R) of such suppressors proved to
be 60+% higher than the other kind. The Rp comparison curves are
available at
http://www.vcnet.com/measures
Rich---
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