Bass amp to Power amp conversion? (70's Yamaha B100II)

[g1]

The only schematic posted was in post #6 and it is working.

[Jazz P Bass]

Here is the complete SM: B100-115SEYAMAHAServiceManual-EN.pdf

[J M Fahey]

Was just rereading this old thread and on checking the schematic found that what the OP wanted to do ... was already fulfilled.

This "Bass" amp has actually quite the Fender Blackface preamp, with Fets instead of tubes, basically same as the Yamaha Guitar ones minus the Reverb.

And very similar to Roland JC something (or the little orange cubes) , again the plain preamp without effects, but as is must be *very* usable with Guitar.
Obviously, the "clean Jazzy Twin Reverb" type of sound, since it incorporates NO distortion at all and you just canīt "set everything on 10 and wail" because of the very clean SS power amp, with tons of headroom , Service manual says the "100W" amplifier must reach 10% distortion (which is *just* noticeable in a Guitar amp) at .... 140W RMS

Of course original 15" speaker is a Bass type, but if driving a couple Guitar speakers this amp must be killer loud and clean.
And for dirt, as suggested earlier: "pick your own poison" ..... er .... Distortion Pedal.

As is, up front, no need to go straight into power amp at all, or you will lose the Fendery EQ it already has, just look at their own TSC type tone controls curve, kindly supplied by Yamaha, basically same curve as classic Blackface Tone Controls. .

As Enzo said: killer Service Manual, one of the best.

If I were a Guitar player and had one of these today, would either turn chassis into a head and drive a 4 x 12" or replace original Bass speaker with, say, an EVM15L ........ in both cases: stand back !!!!!!