Mark IIC - footswitching the EQ and reverb

[Tuna141]

The Mark IIC manual states that there is an a stereo jack near the preamp tubes, that will allow you to switch turn the EQ on/off and increase /decrease the level of reverb using a footswitch.

Well, after many years of ownership, I decided to give it a try. It didn't work -the EQ never turned off or ON and there was no change in the reverb tone.

Has anyone ever tried this? Does it work? Are there any tricks to it?

 

[Boogiebabies]

Did you use a stereo jack with a dual footswith?

I use the Mesa and it works fine, but the reverb never had any change in effect.

One of those cheap black dual button switches will work as well as long as it has a stereo jack. It needs the tip to short the reverb and the ring to short the EQ in order to work. If you use a normal 1/4 inch footswitch, it will only turn your reverb on and off.

 

[Tuna141]

BB - thanks for the reply.

Yes. The first thing I tried was the 2-button footswitch that came with my Vox AC30CC (switches reverb & tremelo). It's a stereo jack. I even tried pulling it oout of the jack a little, but still no luck.

After that didn't work I tried using the 1-button Boogie's Lead/Rhythm switch and didn't notice any change with that either. I figured I'd at least get either the EQ or Reverb to switch with that mono plug.

I also messed with the EQ switch on the front of the amp to see if that had to be in a particular setting for the footswitching to work, and it didn't seem to make a difference.

Any ideas?

It's not that big of a deal. I thought it'd be nice to be able to footswitch the EQ for a different tones....oh well...

 

[Boogiebabies]

Maybe the contacts are bent inside the amp. If you put the switch in the wrong jack and click the left button, it shuts the preamp down. It does the same with a single button switch with a standard 1/4 inch jack. If you have a standard footswitch, try both jacks and see which one switched in the reverb or shuts your preamp down.

Just double check that you are in the right socket.

From the back of the amp the EQ/Reverb is the one on the right.
The preamp out is on the left.

 

[Tuna141]

Good suggestions.

I am positive I plugged into the correct jack - I was very careful and knew that the jack on the left (from the back) was the preamp out. I used a flashlight to be even more sure I got it right. When I toggled the footswitch my preamp did not shut off - nothing happened at all.

I too was thinking about a possible bent jack. It did feel like the cable/plug was grabbing properly when I plugged it in because I had a hard time removing it - I even burnt' my hand on a not so cool power tube while trying to pull it out (lol).

I wanted to make sure that someone actually tired the footswitch feature and it worked. When I get some time, I'll pull out the chassis and take a look at the jack. Maybe a wire has broken off or like you suggested, possibly the jack is bent.

I'll let you know if I find anything...
Thanks.

 

[Boogiebabies]

The blue wire off the jack is for the reverb and the brown is for the EQ.

Do you have any reverb at all?

 

[Tuna141]

Yes, the reverb works fine, and so does the EQ. In fact everything on the amp works perfectly.

Thanks for the wire color/functions - it may be helpful during my troubleshooting.

You did mention that the switches simply work by shorting the signals to ground. When I get some time, I plan on simply using a wire/jumper to short the signal to ground right at the jack to see if that works. Maybe the footswitch I was using can't be used for switching the EQ & reverb for some reason.

Thanks again....

 

[Boogiebabies]

The Reverb switch is shorted to ground with the shorting jack. When you insert the footswitch, it basically shorts the connection on the V3A cathode and lifts the ground to the tube so no signal can pass. The EQ is just a bridge to inerrupt the voltage. It uses the sleeve of the plug to bridge the circuit when the footswitch is inserted. It's a bit more detailed because of the on/off/auto function, but thats basically how it works. It's an override depending on the EQ switch. I would assume that your footswitch may be the culprit since you have a tight connection.

 

[Tuna141]

Success! Well at least partial success...

I plugged the stereo plug from the Vox footswitch cable into the Boogie's EQ/Rev jack and messed around with shorting the tip and ring to the sleeve (ground). I was able to get the EQ to turn ON & OFF using the shorting method. I now know that the front EQ switch must be set to EQ OFF (down) for this feature to work.

After getting the EQ to switch by shorting, I tried connecting the Vox dual footswitch to the stereo cable to see if it would also switch the EQ. It didn't work.

I had no luck getting the reverb to switch at all. I'm guessing that the wire may have broken off at the jack inside the amp. I really don't care about this feature, so I'll just check it out next time I open-up the amp.

I also tried the Mesa Lead/Rhythm footswitch connected to the stereo cable and that did nothing. Then I plugged it's regular mono cable into the EQ/Rev jack and tried it again, and that also did nothing. So, maybe the footswitch with its mono cable will normally switch the reverb, but had no effect on my amp due to it's broken wire?? (just a guess).

Anyway, I'm psyched that I can footswitch the EQ, now I just have to build a footswitch pedal for it.

Once again, thanks for your help Boogiebabies!

 

[Boogiebabies]

The reverb works through the jack. The tip uses a shorting jack to connect the cathode circuit. If your reverb works, the shorting contact must be working. I have had situations were after plugging in a reverb/EQ footswitch and the reverb was somehow turned off. It would only come on until I switched the reverb back in and pulled the footswitch cable.

I am glad you are getting somewhere.

 

[Tuna141]

Welll...time to resurrect this thread...

I bought some parts and wired up an AB-Y footswitch for my Vox last week. This week's project is a dual footswitch for my IIC. I've already made the cables and now need to wire the box. The box will have two switches and I want LEDs indicators for each function (ability to switch between channels and to be able to tturn the EQ ON/OFF).

I'm all set with the channel switching portion, but am having trouble with switching the EQ: The EQ switches ON & OFF OK, and the circuit can power an LED, but once I connect the LED to the circuit it automatically switches the EQ back ON. I tried increasing the value of the LED current limiting resistor, but that didn't help. Maybe it can't be done without using external power (i.e. battery)?? Any tricks or ideas?

 

[Boogiebabies]

You will need an external power supply. The EQ engages by shorting to ground and the Reverb only passes 2.6V to bridge the circuit.

A friend of mine built the exact footswitch a few years ago. He sent me a schematic, but I have to dig it out of the archives and scan it.

Send me a PM if you are interested.

 

[Tuna141]

****... that's what I was afraid of...

I really didn't want to have to add external power because I used a single stereo jack for the channel switching and EQ switching signals (i.e. 2 signals and a common ground). So, that means that I can't use the "automatic ON/OFF" trick with the stereo jack, and would have to use a separate "manual" switch to turn the power ON/OFF.

Thanks for your schematic offer BB, but I'm all set with that respect. I think I'm just going to build the box with a switch and LED for switching the channels and just a switch with no LED for the EQ. I would have added an LED for the EQ if I could have done it without adding external power.

Thanks again!

 

[Boogiebabies]

No prob.

He used a 9V battery.