VFS2A VOX footswitch question.

aienco

New Member
Joined
May 18, 2022
Messages
14
Reaction score
4
Hello all from down under once again... I have a Vox amp and only posted here once before. Been informed this is as good a forum as any other for Vox stuff?

I have been battling with, what I thought would be a simple issue, for some time.

I have built a Vox VFS2A footswitch. For those unfamiliar with these, it is a simple two button foot switch with LEDs. One turns reverb on and off, the other tremlo.

Tremolo works fine with LED and all. However the Reverb will only work if I disconect the negative of the LED. I am using a switched stereo jack and a sp footswitch. The amp supplies voltage to the output of the foot switch. It is around 16V. The tremolo works because when you plug the footswitch in, it is in the open state. So the ground and signal are not making contact. So when switched, they make contact and I just connect the LED through a resistor to the same points.

The REVERB when you first plug in, is in a closed state. So the signal and ground are making contact and when I switch to open the contacts the reverb works fine. UNTILL I connect the LED. The led is connected to the signal of the reverb and the sheild. Reverb does not work, but led does. Disconnect the Shield and the Reverb works, but the LED doesn't?? I know I can do this with a battery. But I know this is NOT how vox do it. All the diagrams and schematics for the vox footswitch do NOT work properly. All links I find to the schematic do not work.

I have been trying for a while to find a way of separating the sheild into two so the one that goes to the reverb LED is not connected to any other sheild.

Any guidance would be gratefully appreciated. I have invested so much time and money in this, that I would have been far better off just buying a new vox footswitch to start with.
The first image is what I started with. The 2nd is where I am at now.
 

Attachments

  • 1.jpg
    1.jpg
    951.5 KB · Views: 3
  • 2.jpg
    2.jpg
    926.4 KB · Views: 3

Jon Snell

Active Member
Joined
Apr 12, 2020
Messages
151
Reaction score
131
Location
Jurassic Coast, England
A clue to the model number and type of your VOX amd would help as there are subtle differences in the foot switches.
Here is the only available schematic from Korg. We can tell it is from Korg, check out the STERED Plug 🤣
 

Attachments

  • Screenshot 2022-05-31 at 07.53.34.png
    Screenshot 2022-05-31 at 07.53.34.png
    83.4 KB · Views: 5

PelliX

Well-Known Member
Joined
Jun 16, 2020
Messages
2,550
Reaction score
5,026
The REVERB when you first plug in, is in a closed state. So the signal and ground are making contact and when I switch to open the contacts the reverb works fine. UNTILL I connect the LED. The led is connected to the signal of the reverb and the sheild. Reverb does not work, but led does. Disconnect the Shield and the Reverb works, but the LED doesn't?? I know I can do this with a battery. But I know this is NOT how vox do it. All the diagrams and schematics for the vox footswitch do NOT work properly. All links I find to the schematic do not work.

Could you confirm the values of the resistors you used? I don't actually have the footswitch for either of my VOX amps, otherwise I'd gladly inspect its guts. Have you tried increasing the resistor on the Reverb switch side?

I have been trying for a while to find a way of separating the sheild into two so the one that goes to the reverb LED is not connected to any other sheild.

No point in splitting, the shield is connected to the chassis, aka common ground in the amp itself.

Any guidance would be gratefully appreciated. I have invested so much time and money in this, that I would have been far better off just buying a new vox footswitch to start with.
The first image is what I started with. The 2nd is where I am at now.

Depends, if you learn something this way, it may still be a better deal in the end, right? :)

I gather you're quite new to making these sort of devices - welcome aboard! That said, I would either 'omit' the shrinktube until you have a working layout (no shame in putting this together on a breadboard first if you feel more comfortable that way), and when you do install the shrinktube - heat it ;)

Quick afterthought:

I am using a switched stereo jack and a sp footswitch.

I can't make it out on the pics, but I presume you've got the right contacts for the switched jack? No need to use a switched one here, but it won't hurt either - provided it's wired correctly.
 

aienco

New Member
Joined
May 18, 2022
Messages
14
Reaction score
4
The resistors play no part in it. They just limit the voltage to the leds and they work. 470 ohm.
The shield in this case is actually not attached to the case as the socket is an insulated socket.

I really hope I learn somthing. So far I have learned that this is expensive and time consuming if you are not sure what you are doing.
 

PelliX

Well-Known Member
Joined
Jun 16, 2020
Messages
2,550
Reaction score
5,026
The resistors play no part in it. They just limit the voltage to the leds and they work. 470 ohm.
The shield in this case is actually not attached to the case as the socket is an insulated socket.

I really hope I learn somthing. So far I have learned that this is expensive and time consuming if you are not sure what you are doing.

Uhm, I'd be looking at a higher value there, maybe 1K5, maybe 2K2. Sure, you can have an insulated socket, but it's a TRS connector on the amp side - so S(hield) will always be shield unless you put in a TRRS jack or something else with an extra conductor - but even then, they would be bound at the amp. Long story short: that's not your problem. :)

The AC15 uses a 3k3 pull up resistor from the +15v supply.
The pedal resistors need to be more than 3k3 to allow the pedal to work.

I think Jon has a point here. Would you care to try this?
 

aienco

New Member
Joined
May 18, 2022
Messages
14
Reaction score
4
Where are you suggesting a pull up resistor? The only resistors are on the Anode of the LED to lower the voltage from 16V to 2V. A 3k3 resistor in its place, would render the LED in active?
 

Jon Snell

Active Member
Joined
Apr 12, 2020
Messages
151
Reaction score
131
Location
Jurassic Coast, England
R39 and R70 are pull up resistors.
Ths is why I suggested the value;
It's not rocket science to know that the base of the switching transistors require at least 0.7v to make them work.
Could work as low as 1k8 as there is an LED to help with the voltage drop.
 

Attachments

  • Screenshot 2022-05-31 at 07.53.34.png
    Screenshot 2022-05-31 at 07.53.34.png
    71.1 KB · Views: 3
  • Screenshot 2022-05-31 at 09.43.18.png
    Screenshot 2022-05-31 at 09.43.18.png
    64.7 KB · Views: 3
  • Screenshot 2022-05-31 at 09.43.44.png
    Screenshot 2022-05-31 at 09.43.44.png
    57.2 KB · Views: 3

aienco

New Member
Joined
May 18, 2022
Messages
14
Reaction score
4
Sorry for my ignorance, It works fine for the Tremlo, however for the reverb it doesn't. I only assumed it is because the Reverb is in the closed state when off and open when on. The LED Ground Cable on the reverb is what stops it working. If I disconnect the ground, it works but no led. So I have been going about this all wrong. I just by chance right now came across this diagram attached. It wasn't there the last few days nor earlier today.
Does this seem to be the way it should work?
 

Attachments

  • voxfootswitch.jpg
    voxfootswitch.jpg
    298.8 KB · Views: 3


Top