Bass Pot Not Functional / 5F6A Bassman

[plexi50]

Hi all you ampomaniacs! How have you been? It's been a while.

I have one of the strangest issues on an amp i have ever run across. It is a Bassman 5F6A and the bass pot has no noticeable interaction what so ever. The 1 meg A pot is good. I also changed it out as a last resort but put the original back in afterwards. I have tested several .1 tone caps and they are all good trying alternative caps here and there. .022 - .047 - .1 etc.

The wire to the bass cap to the pot itself is good and has continuity. I'm not drunk nor do i drink. I may start again. Not really.
What in outer space may be the cause of this. Because it makes absolutely no sense and i am starting to feel like a dumbass.

I just laughed! It's actually funny at this point!

[sluckey]

Is this a real 5F6A or a clone? If clone, did it ever work? The tone caps should be 250pF, .02µF, and .02µF. Are the treble and mid pots the correct value.

Don't you have a real 5F6A that you can compare?

[bnwitt]

Or is it a PCB reissue?  Have you checked the Mid Pot connections from the Bass pot?

[plexi50]

It is a 1977 Traynor Bassmaster that i made a few changes to the fish eye board. The Volume's-Mid-Treble-Presense work fine. Yes bass pot functioned when it was a Traynor Bassmaster. Yes i have a real 59 bassman and have built many clones in the past. This is weird!

[sluckey]

It is a 1977 Traynor Bassmaster that i made a few changes to the fish eye board

My crystal ball suggests a wiring error or incorrect component value.

[plexi50]

It is a 1977 Traynor Bassmaster that i made a few changes to the fish eye board

My crystal ball suggests a wiring error or incorrect component value.

My ball says the same thing. But it don't get any simpler than this. The only thing i think it could be is there may be a wire under the board on that particular eyelet that i am using. I'm going to lift the bass cap to treble cap lead off the board. Right back. Waiting for solder gun to heat up.

[plexi50]

No change. I just did find an oscillation though around the pot wires. Im going to reverse the treble pot with the bass pot. On the traynor the treble pot is at the end of the control panel next to the presense pot and the bass pot is the first pot from the volume pot. Long wire leads. That's got to be it. Will tell in a few.

[plexi50]

No change. Bass pot is producing nothing in tone change. 

[John]

It's almost got to be the ground lug of the bass pot is not providing a path to ground. Or there is a ground missing *somewhere*.

[John]

http://el34world.com/charts/Schematics/files/fender/Fender_BASSMAN_5F6A.pdf


If that's the right schematic, your bass pot "end lugs" should show zero ohms to the bottom lug of the treble, and top lug of the mid pot. If your treble and mid pots are working, I think it's gotta be that. (bad connection)


I see the layout has the treble connected to the bass pot wiper. For yucks, gator clip the wiper to the outer lug of the bass pot. 

[plexi50]

I hooked the bass pot as shown in the AB763 Super reverb and i have bass. Why wont it work the way i have always done 5F6A & Marshall builds?  Weird.

[shooter]

Why wont it work

I have watched otherwise great minds "loose it" over ?'s like that, and I don't help by saying, dude, it works, lets go rock climbing

[PRR]

> I hooked the bass pot as shown in the AB763 Super reverb and i have bass. Why wont it work the way i have always done 5F6A

What is the difference?

[plexi50]

The same other than the Super reverb having a plate driven EQ vs the 5F6A cathode driven EQ.

[Apexelectric]

Just recently had a similar issue. When I took the mid pot out of the equation and replaced it with a 6.8k resistor then it worked fine. Might look to see if your mid pot is your issue.

[plexi50]

Just recently had a similar issue. When I took the mid pot out of the equation and replaced it with a 6.8k resistor then it worked fine. Might look to see if your mid pot is your issue.

Well it works but i have not run into this problem before. Something new to ponder i guess? Nay.