wiring question - volume pot with extra resistor?

[simonm]

I looked under the hood of my Magnatone Mark III today. It's a single pickup guitar from 1957, and I didn't see what I was expecting. Firstly, there is a 0.05 100V ceramic disc capacitor rather than an axial /PIO type, and secondly there is a 47K resistor between lugs 2 and 3 (or is it 1 and 2, I can never remember) of the volume pot. It looks like this - like Gibson '50s wiring + the resistor:



It seems that ceramic disc caps were around in the '50s. They would have been relatively expensive, but it's not inconceivable that it's original, but a replacement is more likely if the orig died. I'm more perplexed by the resistor - is it effectively limiting the power of the pickup?

Has anyone seen this arrangement before? The guitar is in very good condition, has been in its case for x years and is all original, with no play-wear or other mods.

I didn't check the pot value (doh!) but the tone pot is 100K, so maybe the vol is the same. Codes are mid 1957.

The soldering looks like it could be original, but maybe the resistor has been added? What do you think?





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[frus]

the resistor in that place would make the taper "more logarithmic", probably the pot is linear so this helps it get somewhat logarithmic feel
see here:

http://www.geofex.com/article_folder...ets/logpot.gif

[simonm]

the resistor in that place would make the taper "more logarithmic", probably the pot is linear so this helps it get somewhat logarithmic feel
see here:

http://www.geofex.com/article_folder...ets/logpot.gif

All roads lead to geofex!

Thanks a lot!
It is a linear pot, and I was thinking it might be a taper thing, nothing else would make sense, but didn't understand why.

[frus]

read the whole article then if you're interested

The Secret Life of Pots

[simonm]

i read it before, about 10 yrs ago, but totally forgot about it. R.G: what a guy!

[Chuck H]

That resistor, being connected to the grounded and center lugs, also reduces the pots maximum load to only 47k!?! Which seems pretty low for a guitar. Do we know if this guitar is stock? perhaps this is an error on the part of someone that rewired it.

[Steve A.]

...there is a 47K resistor between lugs 2 and 3 (or is it 1 and 2, I can never remember) of the volume pot.

I always thought that the numbering on pots was arbitrary but for most factory schematics that actually number the terminals "1" is the CCW outer terminal typically grounded in guitar controls, "2" is the wiper and "3" is the CW outer terminal typically ungrounded. I would have switched 1 and 3 if it was up to me but their numbering system does make sense because you can have a volume control with just the wiper and the grounded terminal. It isn't a potentiometer (which requires 3 terminals) but it does cut the volume as you turn the knob CCW (they used exactly that configuration as the volume control in my 1937 Rickenbacher Silver Hawaiian steel guitar. )

As for your picture I really doubt that it is factory wiring because of the flux left on the solder joints to the pot case- and the funky way the cap and resistor were added. Just my take on it...

Steve Ahola