>
>Sounds almost as if the plate blocking capacitor is bad such that
>the tank is only loosely coupling to the tube (that could explain
>the weak dip, and the low output power).
>
/\ in my experiences, when transmitting capacitors fail they short.
cheers, Mike
>
>
>----- Original Message -----
>From: <nospam4me@juno.com>
>To: <amps@contesting.com>
>Sent: Tuesday, May 29, 2001 7:38 PM
>Subject: [AMPS] care to take a guess..? Alpha problem
>
>
>>
>> -
>> Hello there,
>> -
>> A non amps member, Bob W0YVA Emails me with
>> a problem he's having with his just purchased used
>> Alpha A77. Care to take a stab with your opinion of
>> the problem..?
>> -
>> I have directed him to watch the amps archive for
>> your answers. Below is a copy of his text to me...
>> 73's-skipp
>> -
>> [snip]
>> : Here is what I have:
>> : This is a "new" A77 (looks like never used) -
>> : Serial 2556.
>> : Seems to be okay except very low power output
>> : (200 watts or so) with 80 watts drive. There is
>> : plenty of grid current. Applying drive results in
>> : significant plate current (800ma or so) which
>> : can be dipped (the dip is very shallow) for
>> : "max" power. HV reads normal. Power is
>> : being measured with Bird wattmeter using
>> : 5KW Bird dummy load. Problem appears on all
>> : band segments.
>> -
>> : Here is what I have done:
>> -
>> : 1. Replaced 8877 with known good tube - no
>> : difference.
>> : 2. Checked bias directly at 8877 socket -
>> : switches properly from high to low with
>> : drive applied.
>> : 3. The zener, D13, seems okay - checked
>> : with ohmmeter.
>> -
>> : Where is the power going with all that plate
>> : current? Weird.
>> -
>> : Suggestions for what to check? The plate
>> : tank components all look good - no evidence
>> : of heat anywhere.
>> -
>> : Any help would be appreciated.
>> -
>> : 73, Bob
>> : W0YVA
>>
>> ________________________________________________________________
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>> --
>> FAQ on WWW: http://www.contesting.com/FAQ/amps
>> Submissions: amps@contesting.com
>> Administrative requests: amps-REQUEST@contesting.com
>> Problems: owner-amps@contesting.com
>>
>
>
>--
>FAQ on WWW: http://www.contesting.com/FAQ/amps
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>
>
- R. L. Measures, 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
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