Fender Bassbreaker 007

[lowell]

Ok. First one in my shop. Multiple PCBs and lots of molex connectors. Anyone got ahold a schematic for these yet? Treble is acting like a volume. I traced the caps that I see connected to the Treble pot and none of them read dead short.

[Enzo]

Phone call to Fender and ask?

[lowell]

Emailed em last night, but yeah a call is probably ideal.

[lowell]

Nope, won't provide it.

Guess I'll be doin' this one blind

[nosaj]

Ok. First one in my shop. Multiple PCBs and lots of molex connectors. Anyone got ahold a schematic for these yet? Treble is acting like a volume. I traced the caps that I see connected to the Treble pot and none of them read dead short.

Give us some board numbers maybe pull something that way. This is the 7watt?


Thanks, nosaj

[nosaj]

Give us some board numbers maybe pull something that way. This is the 7watt?


Thanks, nosaj

May not be the answer but heres some links for thought on the issue at hand.
Vintage Amps Bulletin Board ? View topic - '59 Bassman Treble down = Volume Up.

Tone controls acting like volumes! Need Help!

Hope they help.

nosaj

[lowell]

I had to step away for the rest of the day. I couldn't stop thinking about it though, and realized it's gotta be that the mid/bass section isn't passing signal. That'd make the Treble act as a volume since it's the only one passing signal. The amp definitely sounds THIN too. Time to bust out ye ol scope.

[Enzo]

But out the ohm meter. From the bottom end of the treble control, what resistance to ground as you rotate the bass and mids controls.

[pdf64]

I've seen credible reports of this issue occurring with DRRIs etc; it seems that the pots short somehow and that a squirt of pot cleaner can fix it.
It can't hurt to try it!

[lowell]

That seems SO unlikely, but I believe you... I'll try it. And I'll check ohmage.

[lowell]

WTH!!!!!!!!!! I sprayed the mid/bass pots - fixed!!!! Thanks pdf64!

Enzo, there was only 54ohms to ground from bottom of the treble pot, before spraying.

[lowell]

Cut out again shortly thereafter, cleaned em all twice again and it seems solid. Gotta be this humid salty air.

So, theories on this? Oxidation conducts well enough to cause the 54ohm "short."?

[Enzo]

I would suspect contaminants inside the pot, this is not a very old amp, right? Like maybe a tiny flake of metal inside riding in the lubricating goo.

I guess I was wondering, while it works, what range resistance do you see as you turn the bass and mids controls from zero to max while reading the low end of the treble. I am assuming in my head something similar to a zillion other Fender tone stacks.

[lowell]

Unfortunately the owner was on his way to pick up another amp and grabbed this one too so I can't take the measurement.