Weird tone pot dead zone - Please Help!

[TheLarch]

Here's my dilemma with some background - Please Help!:

I have a Reverend Rumblefish XL that I love - totally my #1. Recently, I noticed it starting to display some odd grounding noise that had not been there previously and the tone pot was acting up by starting to feel a bit "notchy" and noisy when turned.

I replaced the noisy tone pot with a CTS 250k audio pot (which I confirmed through codes is an exact replacement of the older pot). Volume pot is a CTS 500k and the cap is an All-Parts Vitamin Q 0.022uf. There is a 3-way switch for choosing between parallel (top, toward strings in playing position), single (in middle) and series, (bottom, away from strings). I carefully re-did all of the wiring as it had been, but now, when I sweep the tone pot to almost fully open (probably 90% of the way) it gets a bit quieter and then goes silent when fully turned open. The bass is totally usable as-is but I want it to be 100% as it is my favourite.

Any ideas as to what this could be??? I thought that the cap could be a problem but I tested everything with it out of the circuit and the problem occurred regardless.

Thanks in advance for any and all help!!!

Stephen

[TheLarch]

Some photos:





Please help - I'm totally perplexed!!

[capnjim]

Maybe its an audio/linear taper thing? I'm not 100% sure how that works, but there are 2 kinds of tapers and maybe you got the wrong one?
Put a multimeter on the pot and see how the resistance changes...you'll know for sure.

[TheLarch]

Originally Posted by capnjim

Maybe its an audio/linear taper thing? I'm not 100% sure how that works, but there are 2 kinds of tapers and maybe you got the wrong one?
Put a multimeter on the pot and see how the resistance changes...you'll know for sure.

I also thought that could be the issue but the original pot codes (5666000) translate to a 250k audio pot and the dead zone is happening with both the new CTS.250k and 500K audio pots.

[capnjim]

That is strange, maybe try changing the cap even if it tests good

[capnjim]

You might want to start at the begining. Try one pickup with one volume and tone. Then the other without the switch.
Maybe its a pickup phase thing?

[top028]

Are you using the shielding tape as the ground? I had a similar problem before. I soldiered all pot cases and hard wired all the grounds together. (it looks like you have a wired ground in the pics, but I can't tell for sure) Maybe there is a ball of solder that fell into the pot. Shoot some cleaner/lube in there.

[Andyman001]

Originally Posted by TheLarch

I also thought that could be the issue but the original pot codes (5666000) translate to a 250k audio pot and the dead zone is happening with both the new CTS.250k and 500K audio pots.

or the new one and old one?

+1 for testing it with a multimeter

[TheLarch]

Thanks to all for the help - it is truly appreciated!

Volume pot is an older 2007 500k CTS and works perfectly fine.

Tone pot is a new 250K audio taper CTS and works fine but for the dead spot - with the multimeter it tested open when it went to the dead zone.

I tried a different 0.022uf cap and the issue remained.

Maybe a dumb question, but could the fact that one leg of the cap joins with the grounding wire that connect the pots and also the grounding wire from the bridge be a potential cause? If this could be a cause, where should that leg go?

Thanks again.

Stephen

[TheLarch]

In another interesting wrinkle, I solved the tone pot dead zone by moving the wire that ran from the input jack inner ring from its original location on the top lug of the tone pot to the joining the bridge ground on top of the tone pot. The general noise floor seems a bit higher but i think that may be due to the 500k volume pot. I might experiment and swap in a 250k volume pot as this bass is plenty loud and I keep the volume around 60% for the best balance.

Thanks again for all of the help!