Notes on Alpha 76 Linear

History

This linear donated to CCC by WI9WI and placed in service in September 2002. Used in CQWW SSB world win at Station # 2. Low output on all bands because of old 8874 tubes. (Four tubes required.)

16 November 2002

Amp would not turn on. Found that the HV metering resistor R11 had been destroyed. 25 ohm, 25 watt wirewound with screw lug mount. Click here for photo (large file.) Cannibalized the inoperative Alpha 78 for a similar resistor and put it in the Alpha 76. (W0NB did this work.) Found evidence (visual) of a severely overheated 8874 from the Alpha 78 and swapped it into the 76. Alpha 76 was operational normally afterward and worked 80 meter position in CQWW CW with no problems.

February 2003

Three new 8874 tubes (Svetlana) installed by W0NB and W9EFL. Now produces full output on all bands.

5 March 2009

Tested at Station # 1. Easily develops full output (1200 watts) on CW and SSB. Made a few QSOs for confidence. Put back in closet reserve in East bedroom.

15 March 2009

Borrowed the power supply board from this WI9WI amp to test the Arizona amp. Cleaned inside. Put the power supply back in for test. All good.

1 March 2018

Took out of closet for testing. Develops about 600 watts (on 40 meters) but trips off on its own for no apparent reason.

Swapped out the set of three purple ceramic Svetlana 8874 tubes for three others. Will do 500 watts on CW, but more drive sees no increase in power out or grid current, even at 70 watts drive. Kicks off on SSB HV setting above 500 watts. Will loop back and see what the value of R111 is. KB7Q

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