[Amps] TL-922 "Spits"

[Larry K4AB]

My TL-922A has a bad habit of very small arcing...I'll call it "spits".

The strange thing, it happens on random occasions, when the amp IS NOT
being driven.   Even in standby mode, seemingly every hour or so, I hear a
faint,
but clearly audible "spit" or small arc.

No visible signs of arcs in the amp, and other than the "spits", seems to be
working
great.

Ideas?

73,
Larry K4AB