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Tunable hum in Heathkit SB-401 RF output

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June 23rd 08, 08:47 PM posted to rec.antiques.radio+phono,rec.radio.amateur.boatanchors

Fred McKenzie Fred McKenzie is offline

Fred McKenzie is offline

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Tunable hum in Heathkit SB-401 RF output

In article
,
wrote:

I¹ve finished refurbishing a Heathkit SB-401 transmitter, but have one
last problem to fix: 60 Hz tunable hum audible on the output. (Hum
modulates the audio.)

David-

When I saw the word, "tunable", the first thing that popped into my mind
was "parasitic oscillation"!

You might recheck neutralization of the rig's finals. The manual
probably covers it. One thing to check, is to see if the plate current
dip corresponds to peak power output.

Fred
K4DII

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