Manual PDF: http://www.thetubestore.com/lib/thetubestore/schematics/Fisher/Fisher-500B-Owners-Manual.pdf
Fisher FM tube stereo receiver model 500-B. From the early 1960s. Rated at 65 watts per channel. Features, high and low filters on/off, one tape in/output, MPX filter on/off, one phono, one aux inputs, mono/stereo selector, channel reverse on/off, loudness contour on/off. Selector for – tape head – MPX stereo – FM – aux – tape, separate bass and treble controls, Also has a tuning eye.