Volume Pedal Help (again^2)

Steve Feldman · From: Central MA USA

This is mostly unrelated to the similar, concurrent thread.

I recently got an Emmons vol. pedal that has only ~60% of the signal strength/output of my Goodrich L120. There is also a slight, but noticable, rolling off of some of the highs. I can think of only two possibilities:
1) The string is not adjusted correctly for maximum output, or
2) The new replacement pot that's in there (some 500K, Type K, made in Canada pot) is inferior to the standard GeoL/Goodrich (Clarostat) pot.

Can anyone advise me how to correctly adjust this string, or determine if the pot is opening fully? I'd like to check out the string situation before I replace the pot.

Any thoughts on whether it's even worthwhile fooling with this other pot?

Thanks a lot.

Steve

[This message was edited by Steve Feldman on 15 September 2000 at 04:50 PM.]

Keith Hilton · From: 248 Laurel Road Ozark, Missouri 65721

Steve, one way to check is to put a ohm meter between the in and out. When the pedal is wide open, ideally, there should be zero ohms. If working correctly, there will be a few ohms, even if rotated fully. The pulley inside this particular pedal is large. John Hugey had his turned down where it was not so big around. I have measured a lot of these pedals and commonly find 20,000 to 80,000 ohms between the in and out when wide open, The large pulley may not be allowing full rotation, or the rotation degree of the pot may of somehow changed. I don't know if the shaft rotation of the pot has changed or what, since the original movement design. I think the old rotation used to be 312 degrees. If the manufacturer has changed the degree of rotation, even slightly, then it won't work as the pedal was originally designed. I am familar with the pots made in Canada, and I think they are as good as Clarostat. The big questions is if the original specifications of the Allen Bradley pots were transfered when Clarostat bought out Allen Bradley. The rotation of pots in Canada may be slightly different than your pedal was designed for.

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John Lacey · From: Black Diamond, Alberta, Canada

Steve, you may want to adjust the pot to come on at different times. Some guys like to have it come on slightly when it's fully upright. To adjust, loosen the set screw holding the pulley in place, rotate the pot shaft with some needle-nose pliers while attached to the guitar and set to taste.

Jerry Roller · From: Van Buren, Arkansas USA

Steve, that is a brand new pot which came from Paul Franklin Sr and you may wish to adust the on position with the pulley to suit your taste but from all I can learn from guys who know, it is a very quality pot.
Jerry

Steve Feldman · From: Central MA USA

Thanks for the info folks. And I know where the pot came from, Jerry, I just didn't mention it.

I checked the ohms between the 2 hot leads of the input and output jacks like you suggested, Keith. 5 ohms when fully open. I measured it while manually holding it open all the way. My Goodrich measures ~0.8 ohms fully open.

I don't know it the difference between 5 ohms and <1 ohm can result in this loss of volume and loss of highs, but I may just go out and swap out the pot because as this thing is right now, it ain't-a cutting it.

Any final thoughts?

BTW - I hope things are getting squared away for you there, Keith with the situationthat cropped up a couple of weeks ago. I never tried one, but you've obviously got a really great vol. pedal. Thanks for the help.

Jack Stoner · From: Kansas City, MO

Steve, check the other open volume pedal thread. I have a schematic for the "Myrick Mod" posted there but it also shows how to wire the standard pot in a volume control. Could be it's wired wrong??

ajm · From: Los Angeles

Theoretically, if it's a 500K pot and there's nothing else in the chain, it should work just like any other 500K pedal. I'm going to assume that it's wired up, or should be, like a normal (whatever that is) volume control.

Open it up so you have access to the three pot terminals. Disclaimer: These are really simple ideas and I don't mean to "talk down" to you, but since I don't know your electronics background, and there is a problem, it pays to look at everything we can think of. If you've already done this stuff, just ignore me.

You'll need an ohmmeter/DMM for this. Also, the pedal is not plugged into anything for this.

A few things to try or make sure of.....

1) Put one lead on the case of the pedal. Find the pot terminal that is connected to this. It's the ground and should be one of the end terminals on the pot.

2) The center pot terminal should connect to the output jack.

3) The remaining terminal is the input jack.

4) Armed with this knowledge, make sure you hook the cords up correctly when using it. (Yeah, I know, but I've seen it done before.) It will probably still work either way, but you may notice a difference in tone.

5) To the best of my knowledge there shouldn't be any other parts like resistors or capacitors inside the pedal. If there is, this may be the problem.

6) I've got an old passive Fender volume pedal, and sometimes getting the string on right is tricky. I set it so that when the pedal is all the way down the pot is at its full on rotation. (I think someone else touched on this.) When it's all the way back you can't hear anything coming through, even though the pot is not technically all the way off.

7) With the DMM measure between the two outside terminals of the pot. Regardless of how the pedal is set it should measure the value on the pot (500K ohms). If it is much less than that (250K on down) this could definitely be the problem.

That's about all I can think of. Any other ideas?

Steve Feldman · From: Central MA USA

Thanks for the help, everyone. I determined that the pot was OK, but the string was not opening it up fully (only ~270 deg as opposed to ~315 deg max rotation). I tried several times to adjust this, but whenever the pot/string was set to open fully (which worked well), it would not close and so I had signal coming through in the 'off' position.

I must have tried tweaking this a dozen times until I finally stripped the hole in the base plate for the set screw. I never could get it. Seemed like the pedal base/platform assembly did not allow enough travel to range from full on to full off for the pot.

Well, I'm frustrated with this thing, but thanks once again for the help.

Steve

Oh - one more thing. Seems like volume pedals that use a string to articulate a pot is using a pretty cheesy kind of technology. No disrespect to any makers or vendors, but it just never seemed so ridiculous to me as it does now.

[This message was edited by Steve Feldman on 16 September 2000 at 09:26 PM.]

Jack Stoner · From: Kansas City, MO

The "string" usually doesn't cause problems and that system is fairly reliable.
The string system is a lot smoother than the gear type that was used on some pedals.

With the Emmons pedal, you have to put some tension on the string with the spring that the string is attached to. If it's not moving through the full rotation of the pot the string is not routed properly (too many or not enough turns on the pulley).

Steve Feldman · From: Central MA USA

Well - I'll retap that foot plate and try again, Jack. I've had that thing configured with every kind of tension and/or slack combination I could figure. Bottom line for me (at this point in time) is that I could never get it to move through the full rotation of the pot. I can force it to operate to the full open position, but that seems to restrict it from closing fully - and vice versa.

Strings just seem like some kind of 'squirrel cage' technology.

I'll try again after I figur out how to tap that hole.

Thanks.

Jack Stoner · From: Kansas City, MO

Steve, I wish I could help you more but the late 80's was the last time I worked on an Emmons volume pedal.

Steve Feldman · From: Central MA USA

Thanks Jack, I appreciate all of y'alls help!

John Lacey · From: Black Diamond, Alberta, Canada

One more thing to check, Steve. Make sure that the pedal can travel it's full length while on the guitar without hitting the floor prematurely with the string mount shaft. Then you'll have to raise the legs.

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