Found Cause of Volume Spikes/Drops: So which is "correc

[JoeTele]

Hi,

I posted a couple days ago thinking volume spikes and drops in my normal channel only BF Super Reverb build might be the result of blocking distortion. Well, I got out the chopstick and realized that I was able to trigger these by gently touching/prodding the wire that runs from 0.1 uf cap in the tone stack to the treble pot (followed a twin reverb treb/mid/bass for the preamp). The sensitive area is right by that pot. As it stands, the stable state is the lower volume, with precise prodding of the wire triggering the spikes. Any ideas as to what is happening and which is the correct volume? This is my first 40W amp and it is VERY loud, even at the "low" power. Could the prodding be creating a short around the tone stack?

Thanks!

JoeTele

[Structo]

Just guessing, but it could be a bad pot.

After getting two or three defective pots, I always test the pot for total resistance and sweep of the pot.

I also measure all components before installing.

Saves a lot of frustration and troubleshooting.

Just checked your other thread.

The blocking distortion that I experienced before is more of a cutting out, raunchy tone.

This can usually be addressed by changes in the stopper values and coupling cap values to the power tubes.

[jjman]

If either side of the 6800R to ground is intermittent, this would cause volume spikes.

[JoeTele]

Thanks for the suggestions! I want back to chopsticking, was able to get the amp to stay in "loud" mode and, sure enough, realized the tone stack was disabled. Eventually, I realized that the real culprit was the lead dress of the wire running from the treble pot to the bass pot (no 6800R, amp has Twin Reverb TMB tonestack), which connects to the same lug on the treble pot as the one that connects to the .1uf cap in the tone circuit. Thus prodding that (.1uf) wire was moving the one that runs to the bass pot ever so slightly. I moved the wire to the bass pot a bit and now neither is susceptible to causing the short with mild to moderate prodding. Glad to know what that was. Now, it might be cool to have that short on a switch ...

Thanks again!

JoeTele