I have a LK 500NTC (no tune) amp that ran well for several years. Now one
of the 3-500Z's (both Eimac)
filament pins came unsoldered.

K4DLI helped me resolder the pin with a torch and silver solder. Just for a
test I swaped the tubes and within a week the other tube had unsoldered.

I had this problem in a Henry 2K with the tube not fully sitting in the
socket but the 3-500Z's are firmly in the socket. I have a new tube socket
to install but is this the only problem? I really see nothing wrong with
the old socket. Filament voltage is 5V as it should be
on all pins.

Ideas?

Thanks in advance.

73 Dave K4JRB