tonestack problem

[andrew]

Hello, I built another Rocket,wired the tonestack as in the Documents, and all was fine except the bass pot was working more like a bass on- off switch.I swapped out the bass pot and this time there was no volume at all except for a very faint signal. I removed the jumper wire that connects the treble and bass pot and the volume came back. I replaced the treble pot and the two .022 caps but I get the same results. Where do I look now? Thanks for any advice.

[Jana]

okay, I'll give it a shot.

It sounds to me like you have a short somewhere in the circuit. The bass is acting like an on/off switch which seems to indicate that as soon as it has some resistance (it not shorting the signal to ground anymore) then you have signal.

Double check all the wiring in the tone stack and verify that everything is as it should be.

Where do you look now? I would suggest the slope resistor. If that was a very low value then you would have the symptoms you describe. Is that resistor the value you think it is?

[andrew]

Hi thanks for the reply. I replaced the volume pot, the 50pf cap, and the 100k slope resistor. No change. If I disconnect the ground lug off of the bass pot the volume comes back. Stumped.

[M Fowler]

Andrew just checking here you did wire the right lug of the bass pot to ground or the buss bar and R9 10k resistor from right lug to ground as well right?

[andrew]

Hi,On the bass pot I wired the center lug with the 10k to ground and the outer lug to ground also. Thanks.

[Firestorm]

What you're describing sounds like a short between the wiper and the ground lug on the bass pot. That would ground out the 10K and both 22n caps so the only signal left would be coming through the 50pf cap.

[andrew]

Hi, I replaced the bass pot earlier but no change. So strange.

[M Fowler]

Thats why I was asking about how you wired the bass pot since you had replaced it. Strange effect going on.

[Firestorm]

Is R9 really 10K (and not 10 or 100 or 1K)? Grasping at straws here...

[M Fowler]

Yes its 10k

[Firestorm]

Wow! You've got good eyes. I can't see all the way to Alabama from here...

[andrew]

10k on the center lug. I disconnected the buss off of the back of the pots and am now grounded at the input jack but it still doesn't right. Maybe its time to just rip it up and start over.

[M Fowler]

Well I used my bifocals to get that visual.

Hey I thought you were referring to the layout

[andrew]

I cleaned off the board and started over using the same parts and pots. I fired it up, it was silent ,then I heard a thump and it worked. Sweet tone flows forth.I never found the problem but thanks for the help.

[M Fowler]

Andrew is the name for the amp Thumper then?