Apologize for the crude dwg, cannot find a schematic anywhere. It's an old "Manatt King" PA from the 40's. Has 3 12SJ7s for a preamp, 6SL7 PI and 2 6L6s. Lots of interesting stuff - DC filaments for the preamp, two eyelet boards full of resistor and capacitors, and a weird PI. Three inputs, two for MIC going thru one 12SJ7 each (#1 and #2 in my dwg), going to a third 12SJ7 (#3) which also gets a PHONO input. Note all three tubes' plates and screen grids are tied together (after various resistors) to the plate of one side of the PI tube (6SL7) thru a 220K. I know it's not an LTP (no common-cathode), or a Cathodyne (single triode PI) or a Paraphase (inverted outputs from the PI plates). I am stumped. The amp works fine, plenty loud, but I want to play with it, see if it needs biasing, get some distortion out of it (for guitar of course!). Any ideas? Thanks!
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Not sure if the PI is drawn correctly... but if the signals are taken from the plate and the cathode of the same tube, then it is a split-load/cathodyne type. In any case, here is an example of what can be done with it.
Fender 5C8 Mod
Fender 5C8 Schematic
Fender 5C8 Mod
Fender 5C8 Schematic
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