Trem unit and signal disruption but only for bridge pickup

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VANRNR
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Trem unit and signal disruption but only for bridge pickup

Post by VANRNR » Thu Aug 04, 2022 10:50 am

The guitar is an American professional II with the Panorama trem unit. Using the bridge pick up only, and regardless of whether it’s being tapped or not, the signal will randomly diminish in volume and quality, but if I work the tremolo arm vigorously in a more exaggerated sense than I would while playing (think repeated divebombs), the signal strength of the bridge pick up will return. This does not happen when using the neck, combined or the rhythm circuit. Things will rock along with no disruption for some random period of time and then the pattern repeats.

My first thought was that the grounding wire beneath the tremolo had depressed into the finish and was no longer making a good ground connection to the plate. This was my best guess even though it was only happening with the bridge pick up. So, I exposed more of the ground wire and also folded a very small wedge of aluminum foil under the wire to enhance the contact with the tremolo plate. This did not solve the problem. (I also inspected the cavity to make sure that the trem unit wasn’t in some way catching on the ground wire and saw nothing unusual). Next, I rigged wire to connect directly from a string to the tremolo plate to see if that would clearly demonstrate a grounding issue, but it made no difference.

I’m stumped, and would appreciate any ideas you folks may have. Thanks!

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timtam
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Re: Trem unit and signal disruption but only for bridge pickup

Post by timtam » Thu Aug 04, 2022 6:17 pm

That's a weird one. Since the bridge pickup is tapped on the Am Pro II, and that's done from a push-push switch - that also appears to carry the ground connection for the trem - that's where I would be looking. See PDF below. Look for possible shorts between bare wire ends, poor solder joints, etc. BTW the wire colours to the switch part are apparently drawn wrong in the PDF.
https://www.fmicassets.com/Damroot/Orig ... master.pdf
"I just knew I wanted to make a sound that was the complete opposite of a Les Paul, and that’s pretty much a Jaguar." Rowland S. Howard.

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camilonava27
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Re: Trem unit and signal disruption but only for bridge pickup

Post by camilonava27 » Fri Aug 05, 2022 2:35 pm

The ground wire for the trem unit should be connected to the push push switch where the pickup is tapped, check that out. Good luck!

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VANRNR
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Re: Trem unit and signal disruption but only for bridge pickup

Post by VANRNR » Tue Aug 09, 2022 3:37 pm

Thanks for the insights and suggestions. I decided on a two-prong approach. First, I inspected the ground solders and found one to be questionable so I reheated it just enough to let the solder flow smoothly. Second, I decided to connect the ground wire directly to the base of the levered plate that holds the strings by attaching the ground wire to the closest Allen screw using a small ring terminal. Fortunately, the factory gave me a couple of extra inches of ground wire to make this workable. I took a picture to attach but I can’t seem to upload it.

It’s been a couple of days and I have played the guitar several different times. I haven’t noticed any of the signal disruption, so fingers crossed, this gremlin has been laid to rest.

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