Ron - W4WA
Alpha made its entry in the amplifier market in 1970. The amplifiers were as
follows:
PA-70A - Used a 3CX1000A7 - Air Cooled. I still have serial number 5.
PA-70V - Used a 3CV1000A7 - Vapor cooled tube - Had a distilled water chamber.
Alpha 77D - First amp. to use an 8877. Same cabinet as the PA-70 series.
Alpha 77DX - Redesigned and larger cabinet styling. Single 8877. More room
inside.
Alpha 77SX - Same cabinet styling as 77DX but used (2) - 8877's I still own
two..
All the amps used an RF drive bias switching circuit wjhich had design flaws
because
of switching problems. In ssb, the last syllable was always clipped...in turn
causing
switching problems in the amp. This resultes in distortion and undesirable
products
to be heard on the air. Was not kind to adjacent channel QSO's.
A redesign of this circuit is available and works superbly.
Regards,
Bob - K4NV
P.S. I do not believe the modification kit is available as ETO was sold some
years ago
and then reacquired by Dick Ehrhorn and moved to a new location.
Ray Heaton who handled amateur sales is no longer with the firm.
ETO sells factory direct only.
K4NV
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