[R-390] Learning about vacuum tubes

[Perry Sandeen]

List,

If one wants to learn about vacuum tubes, Ebay has a list of mostly RCA manuals and some are on CD.

IIRC mine are version RC-21 but any in that vintage will do. Besides learning how tubes and tube circuits work they have listings or the proper voltage levels under the specific tube number.
One quickly learns that at least many SP 600's were built to non- recommended values. I wouldn't be surprised if other name brand B/A radios suffer a similar fate.
Regards,
Perrier