SPDT issue - Thought this was simple...

[ghostsauce]

So I'm in the middle of hacking my Dr Boogey once more.. and I put a 10nf smoothing cap across lugs 1 & 3 of the volume pot, but I put it on an On-Off-On SPDT because I like it both ways.. One side of the switch works and sounds great, and the other side and center OFF kills the signal entirely.

On one side of the switch the signal has to run through the cap, otherwise it's just a straight wire back to the volume pot. It's not a polarized cap.. What's happening that I'm not aware of?

[slacker]

How have you connected the switch? I can't see how you could wire it so the off position killed the signal.

[ghostsauce]

Lug 1 of the volume goes to the center lug of the switch.. Lug 1 of the switch goes to Lug 3 of the volume, and lug 3 of the switch connects the 10nf cap and then to lug 1 of the switch.

So if I'm right, the signal in one position should come in and go straight out Lug1 back to the volume pot without hinderance... In the center position it doesn't go anywhere, and in the 3rd position the signal goes out Lug3, through the 10nf cap to Lug1, then back to volume pot...

I used an On/Off/On because that's all I had, but it should still work I think. Looking at it now I realize I don't need the straight wire back to the volume pot, I think... I can just attach it to the other side of the 10nf cap and send it back there... leaving the center OFF and the first ON as dead connections.

[ghostsauce]

It's the one at the bottom right with the 2 yellow caps in parallel. (They're 5nf each). 

http://ghostsauce.net/random/DBMods2.JPG

[ghostsauce]

It's got to be something really stupid, I guess... cause the other two switches worked perfectly fine.

[slacker]

How you've wired it in one On position of the switch the cap is connected across lugs 1 and 3 of the pot. In the other On position you're connected lugs 1 and 3 of the pot together, lug 1 is connected to ground, so you're shorting the signal to ground.

What you want to do is connect the middle lug of the switch to lug 3 of the pot, then connect the cap between lug 1 of the switch and lug 1 of the pot. Lug 3 of the switch shouldn't be connected to anything.

[ghostsauce]

AHA! Hehe, what a rookie mistake. Thanks man!

[GGBB]

center OFF kills the signal entirely.

Are you sure its on-off-on and not on-on-on?

It sounds like you did this:

  ---------------------------
  |                               |
  |                           VOL3
  |-----C-----|               |
SW1          SW3        VOL2----->
           |                      |
         SW2                 VOL1
           |-----------------|

At SW1 lugs 1 & 3 of the volume are shorted killing the signal because volume lug 1 is ground.  Center on would explain why middle also kills the signal.

In addition to an on-off-on, you need this to make it work in both outside positions:

  |-----------|-----C------|
SW1       SW3          VOL3
          |                       |
        SW2                 VOL2----->
          |                       |
          |                    VOL1
          |------------------|

To use the on-on-on for this so that one outside position is the disconnect, do this:
               
  |              |-----C------|
SW1       SW3          VOL3
          |                       |
        SW2                 VOL2----->
          |                       |
          |                    VOL1
          |------------------|

[ghostsauce]

There, that's better.. thanks for the help! It was an On/Off/On, and so when I hooked it up so that lug3 is disconnected, and Lug1 goes to the 10nf cap combo and then back to the volume pot it now works as was supposed to.

Hehe, this is what I get for trying to do it 20 minutes before walking out the door with it.