Sano 160 V Guitar Amp

[CJ]

needs a fuse holder, so we get to check it out,

6BQ5 push pull into a 12 inch,    160 V model, vibrato, not R which means reverb, kind of rare,

a little history here>

http://larryjohnmcnally.com/sano_amps.html

 

[CJ]

nameplate>

 

[CJ]

holy cow Amperex 12AX7a orange script from Holland, big $$$,

 

[CJ]

either/or chassis if you want reverb, socket and term board unused, do not know make of torquoise caps,

RMC green top ceramics,  seem to be found in cool sounding amps,

6BQ5's are from Britain,  possibly Mullard, most likely Phillips, branded GE.

 

[CJ]

preamp side,

 

[CJ]

pwr side

 

[CJ]

no EIA code on the OPT,  dang it, 

 

[CJ]

schemo with AC and DC, note massive NFB ,  22K/2.2K, might be reason for lack of breakup,  maybe tweak that FB resistor for more crunch,

spk gnd and fuse left off schemo,

this is a Reverb model drawing which includes Vibrato.

 

[CJ]

scope shots, 1st is overdrive, 2nd is sq wave

 

[PRR]

> massive NFB

No, because the driver is a 12AU7, large Rk, so gain of about 9. Final stage has gain a hair over unity. So the open-loop gain is 10, the NFB limits it to gain of 11... there is hardly a trace of NFB at nominal load.

At speaker bass resonance, gain rises, but NFB limits it, reducing cone slap.

I think it is very much in line with many classic Fenders. 820:100?

 

[CJ]

ok we were comparing that AC cathode voltage with the grid voltage, doh, forgot that the cathode and the plate are in series so we use that side of the circuit which has gain over the grid,  thanks PRR!