input jack grounding slop

This forum is for discussions on all kinds of Peavey bass amplifiers.
Post Reply
wingy
New Member
Posts: 1
Joined: Wed Jul 26, 2017 2:20 pm

input jack grounding slop

Post by wingy » Wed Jul 26, 2017 4:14 pm

Hi everyone. First time poster. I have a Peavey Combo 115 whose hi-gain input jack crackles when under high-vibration or when cord plug is wiggled ever-so-slightly. Meticulous ohm meter testing has found the reason, but I am not sure how to fix. I have proved to myself... that the ground is intermittent on that jack. The guitar cord plug (all plugs) have a tiny bit of up/down "slop" but ONLY when the jack nut is snugged down. When the jack nut is loose, the plug has far less up/down slop, and thus the ground stays connected nicely. Also, this problem does NOT happen on the low-gain input jack.

BOTH jacks have been replaced... but not necessarily with official Peavey parts. Still, they are the correct-looking/fitting jacks.... PCB mounted.

Here's what is happening. When the jack nut is tightened, the jack actually gets less-deep. The tip-clip on the jack actually moves a tiny bit forward, toward jack nut, when the nut is tightened. This causes the plug to have a tiny gap between the threaded collar on the jack, and the face-surface on the plug. In other words, when the guitar cord plug snaps into place, the plug is not fully "seated" against the threaded jack collar. About 1/64th of an inch gap is happening (between jack collar and plug "cartridge")... allowing the plug to move SLIGHTLY up/down inside the jack hole. This causes intermittent ground connection as plug vibrates inside the jack hole.

Loosen the jack nut, and the problem is gone, and the plug can't be moved up/down as easily, or at all.

Does anyone know if there were/are some badly-manufactured replacement jacks floating-around on the planet?

It's a brand new jack. I installed it hours ago, and it has the same symptom as the previous jack, which was replaced 6 months ago (and rarely used).

I ordered 3 jacks, about 6 months ago, and immediately installed 2 of them, one for hi-gain, one for low-gain. When hi-gain jack started crackling at a recent gig, I replaced the hi-gain jack AGAIN... using the extra from that previous order.

Were 2 of 3 jacks... received during that order, possibly mis-manufactured by some crappy company? Anyone heard of this before? I rarely use the high-gain input, but we did some outdoor stuff recently, and I needed full "audio welding" (hi gain jack). Of course, cranking-on the wattage... just makes the amp case vibrate even more. :?

Anyway, I am thinking about putting an extra jack-washer or two... BEHIND the amp face-plate, and see if that causes the jack to "maintain its depth" even when nut is tightened. I'm not sure if it will work, but that's the only solve I can dream-up, right now.

Oh yeah, I thought about putting a small amount of solder inside the jack-collar hole... to cause a little extra "squeeze" on the grounding surfaces. But... this might make the plug a bit more difficult to insert, and it seems like a kludge/temp fix.

I ran a tiny piece of copper wire... from under the jack-nut (then tightened it), and pinched it into the metal plug-cover on my guitar cords. Problem goes away. With that little jumper in-place, I can wiggle the plug up/down forever, no problems. This "jumper" between jack-ground and plug-ground... fixes the issue... no matter how tightly I tighten the jack nut. So, I pretty much KNOW that it is the plug... vibrating inside the jack-collar... that is causing the issue.

Strange, huh? Sorry for long-winded post. I've been everywhere... re-flowed all solder, heavy inspection with magnifying glasses, but all that is moot, because... loosening the nut makes the guitar cord plug... tight again (not allowing any tiny up/down movement of the plug - works), and my little jumper wire between jack ground and plug ground... also eliminates the problem. Go fig, huh?

I've heard the term "floating ground", but this is ridiculous. heh.

Thanks for thoughts, anyone. Be well.

User avatar
Enzo
Member
Posts: 9535
Joined: Fri Sep 12, 2008 10:24 pm
Location: Lansing, Michigan

Re: input jack grounding slop

Post by Enzo » Wed Jul 26, 2017 7:17 pm

Do you have the actual original jacks still somewhere? Look at the face of the jack - the surface that would be against the inside of the control panel when mounted. Is there a tiny metal point? On many models, the real jack has that extra grounding point to conect to the chassis. You can find jacks that look teh same but lack the grounding point, they will be noisy.

Post Reply