Marr/Am Pro hybrid wiring problem

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Ozone7
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Marr/Am Pro hybrid wiring problem

Post by Ozone7 » Wed Oct 07, 2020 6:19 am

Hi

I've got a bit of trouble with some wiring that I hope Timtam and other helpful souls might assist with...

As described in the post on my build (sorry this is now in two places), the Jaguar has Kinman pickups and a 4-way (with series additional option) plus a strangle and phase rev.

The Kinmans were a bit of a chore as they came with a hot+ and hot- as well as a ground wire. Which boggled our minds a bit. I've ended up with two problems:

1: No tone knob effect on bright switch engaged positions although works as a volume pot until right at the end of travel when ALL the top end disappears.

2: A far too savage hi-pass applied by the bright switch.

It's wired with the cap values from the Marr circuit (inc the 56k resistor). But the Kinman has a different tonality to the Bare Knuckles and runs with 250k pots like a Strat, so I'm wondering if that's a factor.
The bright/strangle is currently a 0.003
The tone cap is a 0.01 (but on a 250, not a 1m pot).

Any ideas on what the issues are? The 56k is still shrouded in mystery - is it part of the tone circuit and/or is it relevant for the bright circuit?

Thanks in advance.

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timtam
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Re: Marr/Am Pro hybrid wiring problem

Post by timtam » Wed Oct 07, 2020 7:06 am

It's possible (but not obvious) that the Kinmans and 250k pots have made the 0.003uF strangle cap and other stuff work differently (the Marr has traditional jag values but the Am Pro's Vmods have a 0.022uF tone cap with 500k pots). But first thing to check would be that everything is 100% correct. Does your multimeter have a capacitance function ? You need to verify that the strangle cap is really 0.003uF and the tone cap really 0.01uF. What does the tone pot do when the strangle switch is off (cap bypassed) ? And is the ground side of the tone pot cap really grounded (its omission can make a tone pot act like a volume) ?

The DPDT phase switch should come prior to the 4-way (like in the Am Pro) and just flip the +ve and -ve from one Kinman - one of which (+ or -) will then be hot and the other grounded. The pickup (claw) ground wires should be permanently connected to ground.

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Re: Marr/Am Pro hybrid wiring problem

Post by Ozone7 » Thu Oct 08, 2020 6:52 am

Hey Timtam.

Thanks for your thoughts.
Phase rev switch location is correct and all earths are connected. The tone pot works in non-strangle mode.
But it’s all screwy with it applied.

It’s in with my tech now and he’s run out of things to suggest. He’s had two amp builders look at the schematics and they say the strangle is going what they expect.
To my ear it’s unusable.

I also still have no idea why the tone isn’t dumping HF to ground properly with the strangle switch engaged.

Very frustrating.

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