Crazy new frequency thing with my '69 JM

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thisisnickpaige
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Crazy new frequency thing with my '69 JM

Post by thisisnickpaige » Fri Sep 02, 2022 6:42 am

So i have an '69 Jazzmaster with mastery, an AV65 neck and a Bullocks pickup 50s style bridge pickup i bought off Pat (Pacafeliz), that lately it has this awful frequency issue, like a digital distorted filter.
It's this piercing (think cheap distortion pedal, bad pickups, tinnitus) situation going on. Almost like bad modeling amp's version of an AC30; those harsh metallic percussive overtones (think early 2000s British indie rock).
I've tried filtering it out, different amps, different cables, etc; it always comes through.
The rhythm circuit switch has been wonky for a while (need to jiggle it to let the neck come through in the lead circuit, but hasn't gotten any worse). Acoustically nothing has changed, so it leads me to believe something is up in the circuit.
Only mods are a Mastery bridge from years ago, and a swapped volume pot a few years back.
It's always had a percussive sound (see first link below) but now it's intrusive. It's unbearably to play live/plugged in.

Thoughts:
- Could a 60's cap given up the ghost? This thing was pretty grody when i got it: the vol pot was seized open from the first owners acid sweat. (Pat's friend/acquaintance)
- Mastery has the loctite blue on all the springs and screws. Tried the foam under the strings behind the bridge, didn't help.
- Trem is original. Could a loss tension spring be causing this? I haven't adjusted anything.
- It's not fret or nut buzz. This is in the sound

It's not the normal offset overtone thing. The sound is new/has grown after 4yrs of ownership.
It's this harsh brittle metal sound over all positions.

Thoughts? I know it's all a bit jumbled. Link of the guitar to allure the responses.
Image

Links:
Come to Call - Change of Heart (original)
This link shows this guitar's tendency for spanky percussiveness. You can hear the clangy nature of it, so now it's that but over the top. Like that percussive metal tone has overbearingly increased.

And then one for fun because i love this melody. :whistle: :-*
Come to Call - Straight Trudgin’
Jesus

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JSett
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Re: Crazy frequency thing happening on my '69 JM

Post by JSett » Fri Sep 02, 2022 6:51 am

The first thing that springs to mind, what with you saying it happens in all pickup positions, is that the issue is somewhere in the shared wiring.

Is it present in the rhythm circuit as well as the lead circuit? If so, I reckon it's that iffy switch up there...I think it's the ONLY place everything is connected to that doesn't lead to some level of exclusivity once switched. Apart from the output jack.
Silly Rabbit, don't you know scooped mids are for kids?

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timtam
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Re: Crazy new frequency thing with my '69 JM

Post by timtam » Fri Sep 02, 2022 7:18 pm

Further to johnnysomersett's suggestion, a schematic is key to understanding which parts of the JM's wiring is shared between lead and rhythm circuits and which are not. So if you hear the fault with one setting but not another, or alternatively for all settings, it should be clearer which part of the circuit is implicated.
Image
"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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thisisnickpaige
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Re: Crazy new frequency thing with my '69 JM

Post by thisisnickpaige » Sat Sep 03, 2022 8:46 am

johnnysomersett wrote:
Fri Sep 02, 2022 6:51 am
...is that the issue is somewhere in the shared wiring.
timtam wrote:
Fri Sep 02, 2022 7:18 pm
...a schematic is key to understanding which parts [are] shared between lead and rhythm circuits
I'll have to check, but i don't recall if it was the rhythm too.Obviously with all that roll off it might be less pronounced up there. Can let y'all know.
As i'm not good with schematics, could you help me to understand which parts are shared according to this diagram?
Jesus

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timtam
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Re: Crazy new frequency thing with my '69 JM

Post by timtam » Sat Sep 03, 2022 6:53 pm

thisisnickpaige wrote:
Sat Sep 03, 2022 8:46 am
johnnysomersett wrote:
Fri Sep 02, 2022 6:51 am
...is that the issue is somewhere in the shared wiring.
timtam wrote:
Fri Sep 02, 2022 7:18 pm
...a schematic is key to understanding which parts [are] shared between lead and rhythm circuits
I'll have to check, but i don't recall if it was the rhythm too.Obviously with all that roll off it might be less pronounced up there. Can let y'all know.
As i'm not good with schematics, could you help me to understand which parts are shared according to this diagram?
It's just like following a street map. You can see the two independent circuits for the lead and rhythm circuits - mostly what you expect ... all the lead circuit controls are in the lead circuit, and all the rhythm circuit controls are in the rhythm circuit.

The schematic shows that the two circuits first part ways at one pole of the rhythm/lead switch - where the neck pickup either goes into the rhythm circuit or to the lead circuit's toggle switch. And they come back together at the other pole of the same switch, where the two circuits' outputs go to the output jack. Flipping the lead/rhythm switch flips the connections from one circuit to the other at both 'ends'.

So the shared parts are the neck pickup up to the lead rhythm switch, and the section from the switch to the output jack. Grounds are also shared (ie every component that needs a ground gets it from any convenient, common ground point).

So the switch settings under which the fault is evident - and when it isn't - should lead you to the most likely culprits ... based on what components are "in circuit" when the fault is evident.
"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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