Question about my 1967 Fender Bassman

[Stratohawk]

Hello all, I have a 1967 Bassman and I'm trying to figure out what mods have been made to it. According to the serial number it is a 1967 transitional blackline sivlerface. The tube chart says AB165 but it has been serviced and modified about 10-12 years ago right before I bought it. The wiring doesn't look like any pics of AB165 wired Bassman I've seen, it looks more like a cross between AA864 and AB165. I'm trying to figure out which circuit I want to clone when I go to build a Bassman with my father this winter, I'm looking for thick rich tone with lots of headroom like my 67 has.

So can anyone tell me anything about my amp from these pictures?

Thanks
Chris

[soundmasterg]

Its definitely been modded, though what they did is hard to tell from a picture. You would have to trace out the wiring and draw up a schematic of what they did in there.

Greg

[52 Bill]

To my eyes, it looks like the entire amp has been modded or changed. Even the fibre board looks new. The ac cord comes in from the bottom, the power tube sockets, the added pot near the driver stage, all of the wiring to the tube sockets, the output transformer mounting, the choke mounting, the power supply has only two diodes, etc. The basic workmanship is not Fender factory, the lead dress is kind of messy.

What is the history of the amp?

[sgelectric]

It's hard to tell, but the pot by the driver tube appears to be a relocated bias pot that is connected to the bias supply by the black wire.
The two large power resistors that go from the power tubes to ground suggest a cathode bias scheme.
It may be that the power amp has the combined fixed/cathode bias circuit that was implemented in the circa 1968 Fenders.

http://www.webphix.com/schematic%20h...sman_ac568.pdf

Just a guess.

[Bruce / Mission Amps]

KLUGE alert
I don't see a single thing on the board that is original... no carbon comp resistors, after market capacitors... wires don't look original, power tube sockets are not original... etc etc. Just way too much.

Now if you are really trying to copy that thing... I think you are totally on your own unless you want to pay somebody to reverse engineer it, which I doubt has crossed your mind.

Unless you like the way it sounds (and it could sound great as is)... I'd strip all that amateurish crap off, leave the filament string as is and start over.