Or was , extensive mods by Jason Sansome 2007. Numerous problems now. PCB removed , replaced with hard wired tag board. Added valve for reverb tank plus its matcher Tx. Mains Tx changed. Any chance of finding schematic of this mod or some sort of generic overview ?
Instead of the original 3x 12AX7 it now has 2 and 2x 12AT7 and a 5AR4 rectifier
Download the schematic from
-- David dgminala at mediacombb dot net
"N_Cook" <
** You need to find a schem of the Bandmaster-Reverb Amp AA768.Shame all the ones Google turns up are illegible.
.... Phil
"Phil Allison"
** This is probably close enough:Ignore the Vibrato circuit.
.... Phil
I have the diags for AA768, it's not brilliant but fairly readable. email me if you want a copy.
Ron
Ta for that, I have it in the Aspen Pittman Tube Amp vol 3 book which hapens to be a very clear schematic. I think I've found the distortion problem, duff 12AX7 socket pin. Remaining problems are both large Tx only held to the chassis by wishful thinking. And excess hum (for this owner), bad replacement pots (tagged, not the original pcb ones). The output matcher had to be moved to accommodate a different speaker, and not well mounted . Badly blanked off front panel holes for niow deleted functions. Other than the cab little seems original, o/p Tx, choke, knobs, chassis , valve bases and the jewel pilot lamp holder is about the sum of it Luckily surplus Rexine in the amp cavity to salvage for where their pet rabbit has eaten the exposed covering. Researching the output bottles , nice little page about the company, I like the "retro" industrial instrumentation
Or like the AB868 with the vibrato ch removed
Another thing that has remained from the original. That manurey/goaty / caproic acid smell that emerges when Fender (and other USA-made) amps are opened to the air in the UK. No one else has come up with another explanation - so I will stay with the US-patented use of fatty acids from abattoir sources as a part of the formulation of the insulation of transformer magnet wire. Then some reaction to UK humidity or UK-specific microbial action. Not an unpleasant smell , just agricultural, not what you expect to come from electronic kit. This amp has a UK made mains transformer replacement so the smell , if from inside the transformers then from the choke or the output Tx . I deliberately kept the cab in another room this time , no smell there, so not horse glue used in the cab making.
Or like the AB868 with the vibrato ch removed
Another thing that has remained from the original. That manurey/goaty / caproic acid smell that emerges when Fender (and other USA-made) amps are opened to the air in the UK. No one else has come up with another explanation - so I will stay with the US-patented use of fatty acids from abattoir sources as a part of the formulation of the insulation of transformer magnet wire. Then some reaction to UK humidity or UK-specific microbial action. Not an unpleasant smell , just agricultural, not what you expect to come from electronic kit. This amp has a UK made mains transformer replacement so the smell , if from inside the transformers then from the choke or the output Tx . I deliberately kept the cab in another room this time , no smell there, so not horse glue used in the cab making.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.