Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Effects => Topic started by: super&plexi on October 14, 2016, 09:57:11 pm
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Anyone have experience with changing out old pots for new; old A/Bradley orig. 100k actual (2.7 R-139K) for new PEC Canada both sealed, actual reading (44.5R-89.5K)... To mount the new pot I have to cut shaft, grind notch for gear, & either drill hole or notch end for "c" clamp, or the one that has 2 holes & opens w/pliers that use opposing force (name escapes me) Basically I'd rather sell the new pot (paid abt.$18) & try different one if its gonna screw w/overall performance. I've had numerous wahs, & almost every one of oldies (67-72) had pots that read similar to the wider sweep-2-4Rs low, 110-150k high... Did they drift w/age, wear, or were they made that way? I love the way the old ones scream!
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... almost every one of oldies (67-72) had pots that read similar to the wider sweep-2-4Rs low, 110-150k high... Did they drift w/age, wear, or were they made that way? ...
I can't answer about how the pot will sound in the wah circuit.
However, on a Les Paul forum owners of original bursts have noted that the 500kΩ pots in those guitars often "drift" up to 800kΩ or more. The general wisdom there is that the "drift" is due to decades of the wiper scraping along the carbon track, eroding some of the resistive material and thereby increasing the total resistance of the carbon track.
One can imagine the same happening with a wah pot...
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Thanks HBP.... you're always quick with a new piece of info. Got me to thinking about bastardizing one of my older pedals for a pot, but upon checking it again the highest side was still about 89k, but the low side is holding out at about 11 or 12 ohms. That got me 2 figure close enough so I wired up this mess with clips and found out a little more about how the pot works in the circuit.
It seems the high-end comes from the wiper to rear most tab...low Ωīs, & the deeper rolled off tone comes from wiper 2 the front tab closest to the switch...High KΩīs. If the pot was indeed 44Ωīs like I thought, I could just put a few Ωīs resistor in parallel with the middle wiper and the rear most, and had a resistor in series to the front wiper from the switch if I needed it but it looks like the rotation will run out before I even reach the full 89 k.... do you think I should post these findings in another thread in case somebody could benefit from them, and thanks again.
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That 2nd to the last sentence should have read 'and add a resistor', not had a resistor...
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I'm sure the info will help someone down the line...