Possible to control the Boost level on a Vox Pathfinder?

[Little Ricky]

Didn't work as planned. I received the  Pathfinder yesterday and opened it up today. using a 1MA pot I connected the center lug to the junction of R8/Q1 and the outer lug to the junction of R6/Q1.

The pot works as on on off switch about midway it cuts out the volume completely, whether the boost is engaged or not. Makes a sound almost like the Enterprise going into warp and then nothing.

[J M Fahey]

Then you connected something wrong.
And what do you mean by "the" outer lug?
There's 2 of them and they are not the same.
Is it mounted or still in your hands?

[Little Ricky]

Looking at the back of the pot, lugs facing up,I used the left side lug. It's mounted but easily accessible. Wires are attached to the Q1 side of the resistors 

[J M Fahey]

Make these 2 tests:
1) unsolder the wires from the pot but leave the other ends still attached to the PCB.
Play, and switch distortion on and off. What happens?
2) place your ohm meter tips on the pot lugs.
Set it to 0/5/10
Post the resistance values measured.
Thanks.

[Little Ricky]

Thanks.
OK, I'd like to tell you there was a problem with the pot... but I can't. I tacked the wire to the wrong side of the resistor. I corrected it and it works perfectly. Thanks

[Roly]

Thanks.
OK, I'd like to tell you there was a problem with the pot... but I can't. I tacked the wire to the wrong side of the resistor. I corrected it and it works perfectly. Thanks

Yowza!  :dbtu:

[danmahoney]

Hi Guys,
   I`m not great at reading schematics and am still not all that clear on the mod. Can you walk me through some specifics, ie: Are you connecting wires from the 1Meg pot to the actual lugs of Q1, or are you connecting to the resistors (R8, R6)? If the resistors, are you on the Q1 side of the resistors and are you soldering to their contact point from the bottom or top of the PCB? Also could you let me know which lug on the pot goes to where exactly on  the PCB? Thanks so much, any help would be greatly appreciated!
Dan

[Roly]

Hi @danmahoney.

Repeating the circuit fragment from the previous page;



The copper PCB trace that connects C6 to pin 6 of IC1b, C7, R6, and Q1 is basically just a bit of wire.  You can pick up a connection to that anywhere along it on the copper side, or by soldering a wire to the lead of one of the components connected to it (such as R6), anywhere that is physically convenient.  This goes to one of the three tags on the pot.  Looking at the pot from behind with tags up it should go to the left side tag.

The centre tag on the pot similarly has to connect to the trace between Q1 and R8, again copper side or component side of the PCB, whichever gives the shortest and neatest wiring between board and the pot.

HTH

[danmahoney]

Hi @danmahoney.

Repeating the circuit fragment from the previous page;



The copper PCB trace that connects C6 to pin 6 of IC1b, C7, R6, and Q1 is basically just a bit of wire.  You can pick up a connection to that anywhere along it on the copper side, or by soldering a wire to the lead of one of the components connected to it (such as R6), anywhere that is physically convenient.  This goes to one of the three tags on the pot.  Looking at the pot from behind with tags up it should go to the left side tag.

The centre tag on the pot similarly has to connect to the trace between Q1 and R8, again copper side or component side of the PCB, whichever gives the shortest and neatest wiring between board and the pot.

HTH

Thanks Roly, that helps a lot! I`ll probably go with trying to connect to a leg of the resistors. With R6 would I be connecting to the Q1 side (leg) of the resistor as I would with R8?
Dan

[Little Ricky]

I just tacked the wires to the trace side of the board, on the q side of the resistors.

[danmahoney]

Thanks Ricky, with your and Roly`s input it should be easy!
Will have to wait a few days for the pot to arrive but then I`m all set to go. Thanks for taking the time to shoot the pic!
I`ll let you know how it turns out, all the best.
Dan

[Roly]

Thanks @Little Ricky, that's an excellent crisp picture that should answer most of the questions.   :dbtu:

[danmahoney]

Thanks guys, much appreciated!
Any opinions on doing the LED mod at the same time?

[Little Ricky]

I would. You can do both mods right from the back of the pcb.

[danmahoney]

I would. You can do both mods right from the back of the pcb.

Ok thanks Ricky. Two quick questions: what did the mod change about your tone and did you just lift an end or completely remove the LEDs?
Dan