[AMPS] Alpha Amps

[Rich Measures]

>Subject:     Re: [AMPS] Alpha Amps
>Sent:        3/27/1997 1:38 PM
>Received:    3/27/1997 1:42 PM
>From:        Dick Byrd, n4uq@mindspring.com
>To:          amps@contesting.com
>
...snip...
>>Seems that a 2 hole version would last a lifetime at 1500w out
>>regardless of the mode.
>
>Yep!
>>
However, Alpha 77s sometimes experience sudden 8877 failure for a reason 
that is not apparent.  I have tested a number of such tubes. wherein the 
Funderburg Test indicated that gold-sputtering was present.  When the 
anodes were removed, gold plating was missing from the grid--and gold 
melt balls could be seen on the cathode coating with a 30x microscope.  I 
have never been present when such a failure occured, but the vast 
majority of gold-sputtering events occur when normal grid current is 
present, during actual operation when the grid dissipation is well under 
10W.  The 8877 is rated at 25W grid dissipation.  
>
  The 8877 has much VHF gain.   In HF service, this is NOT good news.   
IMO, if the VHF suppressor does not present the anode of the 8877 with a 
low VHF parallel-equivalent resistance (Rp) the VHF gain is not going to 
be low. (note: Voltage gain is basically Mu multiplied by Rp.)



R. L. Measures,ag6k,805-386-3734    


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