Oh gurus of many watts ... I have searched the archives of wisdom but do not
see any reference to an L-4B with a power supply buzz.
I recently picked up this very nice old Drake relic. The amplifier if quite
clean and functions flawlessly. (You know ... only driven by an elderly
gentleman on early Sunday mornings ... )
However, after having been on for a bit yesterday and while helping bust
through 12m and 10m pileups on VP6DX, the power supply developed a buzz - a
"bright" sounding 60Hz buzzing that could not be ignored. Switching the high
voltage to low (CW, 1900v) seemed to make the problem go away; returning B+
to high (SSB, 2400v) made the buzz come back. I tried the usual "gentle
tapping" on the power supply case and checked to make sure all of the
external screws were tight. Then, I cranked up the volume in the headphones
and didn't pay serious attention until the QSOs were in the log. Later, the
buzzing was present even in CW mode and switching to SSB just made it worse.
I relocated the power supply to the floor behind a file cabinet, but the
raspy buzz is just as loud and clear as before - an unacceptable solution.
(I have, however, successfully solved noise problems in my truck by turning
up the stereo and/or using earplugs.)
Help! If anyone can point me in the right direction, I would be most
appreciative. (I do have some experience with amplifier repair and safety.)
I did check to ensure that the signal the amplifier is producing is very
clean and free of any 60Hz crud.
Short of a solution, I can offer a clean 80m-10m amplifier for sale to a ham
who is hard of hearing.
73!
Don Chisholm, K8BB
Pontiac, MI
(248) 451-0545
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