Bob reports back in with many thanks and the
following.
-
[snip]
-
: Skipp,
: Here is a summary to date on my Alpha 77 (PA-77)
: Symptom: Very low power out on all bands (maybe
: 200w or so) Plenty of grid current. Plate current can
: be driven to 800+ ma and exhibits a very shallow
: dip at resonance. Resonance occurs nearly exactly
: where predicted by the manual into a 50-ohm load.
-
: Troubleshooting efforts:
-
: Note: Power being monitored by both external Bird
:and the internal meter (Bird was checked with another
: rig to ensure proper operation). The two agree.
-
: 1. Output vac relay checked both with meter and by
: shorting contacts.
-
: 2. HV checked okay. HV meter reads properly.
-
: 3. Very carefully checked bandswitch and related L's
: and C's - no problem. I can't think there is a problem
: here since resonance occurs as predicted.
-
: 4. Checked (both were okay on capacitor checker)
: and then replaced (one) - no change.
-
: 5. Checked to ensure bias was proper at the 8877.
: Not surprising it's okay since we have lots of plate current.
-
: 6. Substituted the 8877 with a known good tube -
: no change.
-
: 7. Switched out the input network - no change.
-
: What's left ??? :-)
-
: 73, Bob
: W0YVA
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