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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..?
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I have directed him to watch the amps archive for
your answers. Below is a copy of his text to me...
73's-skipp
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[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.
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: 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.
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: Where is the power going with all that plate
: current? Weird.
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: Suggestions for what to check? The plate
: tank components all look good - no evidence
: of heat anywhere.
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: Any help would be appreciated.
- ?
: 73, Bob
: W0YVA
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