>
>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.
>... -
/\ A good vacuum relay Must have a good vacuum. Vacuum relays can not
be checked without using a high-potential tester to measure the
HV-conductance of the vacuum across open contacts. Another essential
test is contact resistance. To measure the resistance of contacts, put
1.00A through the contacts and measure the V-drop across the contacts
with a DMM. For example, a Jennings RJ1A vacuum relay should have no
more than 10mV across closed contacts with 1A flowing. (10-milliohms).
And, with 3500VDC applied to open contacts, there should be under 1uA
leakage.
- Vacuum capacitors also need to be checked with a high-potential
tester. ("high-pot")
cheers, Bob and Skipp.
- R. L. Measures, 805.386.3734, www.vcnet.com/measures.
end
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