[R-390] Capacitor failure

[Perry Sandeen]

List,

Wrote: The gotcha with B+ bypass caps is that you can lose a filter choke (as well as rectifiers and resistors, but, as you note, those are not the end of the world).  I have seen this happen more than a few
times, including to one of my own radios.  Replacement chokes can be very difficult to find.

This is why one makes the 3 fuse mod to a R 390A and adds an additional separate fuse to the SP 600 B+ circuit.  See Andy Moorer’s SP 600 site or the SP 600 anthology for details.  And the most likely cap to short is not a .01 bypass unit but an electrolytic.  That’s why at least on the R-388 and R-390A they used socketed filter caps for easy replacement.

Also the high value of inductance is not necessary any more as one can use those sold for Dynaco replacements sold by Triode electronics and use modern multi-hundred filter caps instead. BTDTGTTS.  (It takes 20 pounds out of a SP 600.)

Regards,

Perrier