Thursday, June 26, 2014

BB King Lucille position # 2  push pull tone circuit

This is a 2 way varitone drop in tone pot replacement. Pushed in it is just your basic tone circuit with a standard .022uf or .05uf (.047uf) radial film capacitor. Pull it out and you have position #2 of the gibson style varitone. Position #1 is bypass position #2 has a filter cap .001uf and the choke with a 10Mohm drain resistor and a 51K limit resistor. I build these with either 250K or 500K audio taper P/P guitar pot made by Bourns. . The 250K being a little bit warmer and the 500K a little brighter. I have had many guitar players tell me position 4 5 and 6 of the standard varitone are useless. To much cut and to dark.I modified the gibson spec on all of my varitones and changed the 100K resistor to a 51K resistor. For bass guitar on the other hand the darker filters are more useful. I can build these for any configuration for Bass or guitar. 

Wednesday, June 25, 2014

A simple mod to add a varitone choke using a push pull tone pot replacement. It also works well as a stand alone mod. Its just an easy way to be able to switch the choke on and off. In the pictures I show how to install both a tone cap and a choke on your P/P DPDT switch. For some installations you may want to wire your varitone switch directly to the push pull switch and send your tone pot capacitor directly to ground.  

Start off with the TL021-RC transformer. What we are after is induction for this reason I am only going to use the primary coil. The primary coil has an impedance of 4Kohm secondary 600ohm and the resistance is 148 primary and 64 secondary. The primary coil has 1320 winding's and 440 on the secondary just in case you want to wind your own.  

Solder one wire to the TL-021-R transformer body snip the center tap wire and you are ready to solder it to the the potentiometer body. The body of the bourns push pull  guitar pot is perfect for the match to the inductor. 
You can snip all of the secondary wires if you want to I usually bend them to the side and they will be covered by tape and shrink tubing in the final stages.

There is a little slot in the bourns pot body that is a perfect fit for the little tab on the coil one tab slides into the slot the other tab will just fit to the base or bottom of the switch body as shown.

I solder the tab to the switch body and a little spot of solder at the bottom where the tab fits into the slot.

You can see now there is one free wire after the coil is attached to the body. you can click on the picture for a larger view. The wire is soldered to the switch lug. The way i have it arranged when the switch is pulled it turns the choke on when it is pushed in it turns the choke off. This is a double pole double throw switch so you have 6 lugs total the center lugs are poles one and two the outer lugs are your two positions or throws. The choke wire only needs to be connected to the closet lug in this example will will call it the left lower lug. The capacitor is soldered to the potentiometer lug #1 furthest to the right in the picture. The other lead of the capacitor is pushed through and soldered to both poles. Snip the excess wire.

Then take a short piece of wire and solder one end to the top right lug as shown in the picture. The other end is soldered to the ground lug on the switch body. Solder a length of wire to lug #2 or center lug on the tone pot and you are all done. When the switch is pushed in the signal travels through the capacitor then to the ground wire that is grounded to the body. When you pull the switch the signal travels through the cap then through the coil to ground. All done and ready to install in your guitar or bass!

Buy one for your guitar or bass pre built and ready to drop in.