[Kenwood] R-820 Problem

[Dr. Gerald N. Johnson, electrical engineer]

Its not the filter capacitors in the power supply, its the line cord
filter capacitors. In radios of that era there was a paper capacitor
(generally) from each side of line to chassis. Often .05 uf. If not
shorted or leaky, they still will draw enough current to raise the
chassis to a voltage that you can feel, and that will trip a GFCI
circuit breaker. They are often on the line side of the fuse (for RF
filtering) and the fuse is only one side of the line. The plug is
probably not polarized so even if the fuse is between the power cord and
the line bypass capacitors the odds are 50/50 that you had the hot side
of the line unfused.

The cure is to replace the line capacitors with .01 / 1600 volt
capacitors rated for line bypasses and use a grounded power cord or a
separate ground on the radio chassis.

Not to say that the old miniature electrolytics and other paper
capacitors in the receiver are fine, they have aged and are not nearly
as good as when new, but your problem isn't them its the line bypass
capacitors.

73, Jerry, K0CQ

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.