Please Help Me Trouble Shoot 64 Bandmaster

[JoeM]

DAB,

People here are trying to help. Your post above about the OP trannie was confusing. Apparently the date codes are a year off. I wouldn't think that to be unusual, Fender probably just using old(er) stock until used up. Though the leads on the OPT don't look like the usual neat wiring in BF amps.

I do have a concern that even if the amp is working properly and to spec, you might not like it. If there was some anomaly in the amp causing a certain distortion, having it restored to the original Fender BM sound might not be what you are expecting. Bashing GW for whatever he did or did not do isn't helping, and we're only hearing your side of the story.

[dumbassbob]

I know people were trying to help But I don't think anyone understood what the problem was... I am Not looking for distortion I have a 100 watt Plexi's for that..I wanted my CLEAN... unmuddy sound back..Your right GW didn't do it He had a flunky do it. All it needs is 3-4 hours of close inspection....I am waiting for a email or phone call from Bruce at Mission amps.All the problems started when this prick stole it...

[km6xz]

It is hard to believe this thread is still going.....
A tech with a sweep generator and scope would be able to tell within seconds most of what has been attempted in this thread[s] in trying to determine if the bandpass is different than it ought to be. The absence of information on the bias status is critical also which would swamp all the prior side tracked directions this thread has taken.
If a tech does do a frequency response plot tell them to use a very high source impedance on their signal generator to simulate a guitar and a typical guitar cable. I say this because the input circuit has been changed in in wiring and added capacitance with unneeded coaxial cable that will roll off high frequencies with a guitar but not with a typical 600 ohm or less signal generator. The original wires that are hanging loose are lower capacitance than the very thin coax. I can't see the details of the input jack wiring but is appears to be different than stock. The shiny blob of solder indicates a recent mod.
I notice that several of the redone solder joints are pitted dull grey in the eyelets, the rough surface suggests crystalized solder. Remove all the solder from those and replace with properly soldering.
The discussion regarding the meaning of "clean" has two different meanings to the techs vs. players so DAB took offense at the notion that people were talking distortion and he was talking about clean. For a tech, ALL amps are distorted and especially all guitar amps and the degree and nature of the distortion determines whether it is a clean musical note or not, and the player will think of the term "distortion" as when extreme waveform distortion as an effect is added. A really, actually low distortion amplifier is useless in amplifying an electric guitar, it would sound very thin and with little character to distinguish whether the note came from a horn or a string since the harmonic content would be very low coming from the transducer in the guitar. The fundamental would the the only dominate wave. The guitar has a resonate filter(actually two slopes when a cable is added) that accentuates any upper order harmonics and to reduce the amplitude of the dominate fundamental but the amplifier needs to have some non-linearity(distortion) for the note to have the complex array of upper order harmonics and intermodulation that tells our ears that the instrument the note was generated by was in fact, a guitar.
Fundamentals, the named note, is the same for all instruments and without the differences in upper harmonic, a piano or flute would be indistinguishable.
So the tech's job is to see what distortion products are there, in "clean" mode and whether the upper harmonics are being handled or being abused by the amp so it sound less guitar-like. A known characteristic signal put into the amplifier and the harmonic content and amplitude relationships between the expected harmonics can be viewed and analyzed. He could just listen but not knowing how that amp normally sounds or variations in conditions, playing or interaction with so many variables that are involved with generating a signal by playing, variations in amplifier performance are swamped by playing variables. In diagnosis, reducing or controlling for variables is essential.
Was the OT changed or not, I got confused.
The repeated blowing of the bias cap is something to inspect closer, why or did it actually fail twice? If a tech can't explain why he changed something, like GW did, often they make up a reason to justify the added expense that does not correct a problem. Techs who shotgun all do that and I think it is not ethical but it is very common in the industry.
Has the bias been verified by a scope for balance and cross-over point? Even if the idle current is measured within spec, it does not say anything about the AC large signal performance.
I suggest going with your amp to someplace where you can play it for the tech and point out exactly what you are objecting to. Often the description losing something in the translation but if you both agree that there is a particular observed behavior is present and that a repair will mean that behavior is removed, there should be less question, doubt or argument. When testing in his shop, try to duplicate the operating conditions back home such as measuring your line voltage and telling him what it was so his variac can be set to the same mains voltage.
If you can't visit his shop for a joint listening session, record the tone that clearly demonstrates the problem.
Good luck

[dumbassbob]

My comments about the filter caps and the grid stoppers was meant to point out things that I saw that were different, like the 220K resistors and the double caps in the treble circuit of the tone stack.

My point was that I've never seen a stock Fender grid stopper hung in the air like that, and that it would be nice to see some better photos of that area of the amp.

The schematic for the AA763 shows the first filter caps as being two 60uF caps in series without the balancing /bleeder resistors. This one seems to have the bleeders installed.

I'll leave this one to you guys.

The caps you think a grid stoppers are the 500pf phase inverter that Gerald Fucking Weber goon put in but didn't solder..I had everything redone back to stock by Skip Simmons repair..The ONLY thing that was wrong with the amp was someone reversed the power tube plate wires..G Weber pulled my amp apart and stuck New crap in it Kept the blue ajax caps This is how the amp looked after I put the coupling caps back in and was shipping it off to Simmons amp repair ..He fixed the amp back to stock in one hour,and only charged me $40.00....Amp works great has a really good tone He asked me if I wanted the 350pf caps pulled I said if they didn't hurt leave them in