Footsw doesn't go to CH2. Works on individual 1/4in switches

[Jiveman]

My original MKV footswitch stopped switching to CH2. CH1 button goes to CH1. CH3 button goes to CH3. But CH2 switches to CH1, for some reason.

The manual channel knob in the back switches to all channels. Also, the individual 1/4 inch switch inputs in the back appear to work fine (using my Voodo Labs 4 channel midi switcher).

You guys think this could be one of the switch relays or something? I'm still under warranty, so I might call Mesa to see what they say. In the meantime, I thought I'd toss it over to the forum for opinions or any possible past experience with this. Anyone?

I don't have another footswitch cable to try right now... But I might get one (because I need the 8-pin one anyways... This one is 7-pin, although it's worked fine so far).

 

[bandit2013]

The 7 pin cable will not allow you to activate the effects loop. They gave me the 7 pin cable by mistake when I got my amp at GC. In case you were wondering the difference between the two.

Does the LED on the footswitch change or not when selecting CH2?

If the manual rotary switch on the back of the amp is working, I do not believe it is related to a switching relay. Most likely due to poor connection with the midi cable. I have issues with a replacement cable (took the 7 pin back to GC for an exchange to an 8 pin, that was a hassle since the manager did not want to do that but I negotiated to have it replaced since I was not going to leave with the wrong cable.)

However, when I have issues, it is the EQ that drops out. It is all in the connector of the cable. Try swapping ends and see if that makes a difference, sometimes that works, sometimes not. The channel selectors on the footswitch are momentary "on" switches that set a digital latch. When you select another channel, it resets the latch used for the other channels. Also probably uses a here is a driver chip in the footswitch, not exactly sure what is in there since I have not been successful in pulling the board out completely. Chances are the switch is not making full contact and the driver defaults to CH1. This is all an assumption of course. Considering there has to be a supply to light up the LED's and a ground (shield of course), the Reverb, Effects Loop, EQ, Mute, and Solo are simple ground switches. The channel selector has to be a binary 2 bit signal on two of the wires (not sure how they coded it, [00, 01, 10]. If one of the connections are loose, only part of the channel information is being sent to the amp. 0x and 1x where X is don't care and assuming that the x is = logic 0 at the amp (has a pull down resistor on the decoder). Yep, probably loose wire or pin to receptacle connection on the Midi interface.

 

[Jiveman]

Yes, I know about the differences between 7-pin and 8-pin, and I've also had the EQ cut in/out before. But this is different.

The LED on the footswitch itself changes to CH2 when I push it, but the amp actually switches to CH1 (say, if I happened to be on CH3 before that, for example). I I was on CH1 and then push CH2 button, then the amp doesn't do anything (although you can hear the relay click like it's doing something), it stays on CH1. So in all cases, the footswitch shows the correct LED for the pushed channel, but the amp only switches to CH1 or CH3.

 

[bandit2013]

I was going to go deep into the weeds, almost willing to take my footswitch apart to study the circuit and provide a list of possible issues that could be part of your problem. However, I am not going to do such, sorry. I did take my footswitch apart once and was a real pain to reassemble. I had different issues and mostly related to the cable but had to make sure it was not a bad solder joint somewhere, only to find a dumb *** ground wire mounting method which placed excessive bow on the circuit board which is not good practice so I fixed it and also re-soldered the DIN receptacle pins on the PCB. I should have taken the time to map out the circuit but I did not.

You either have an issue with the footswitch controller, may be a bad solder joint that finally opened up, or more than likely it is related to the 8pin DIN cable. (it is not MIDI, I made that mistake too but could not find such since MIDI standard uses a 5 PIN DIN ). The one I have is problematic. Mostly works unless I move it which typically results in relay chatter in the amp. Good reason they do not provide 10W/45W/90W power mode selection on the footswitch.

 

[bandit2013]

Here is a link I found, now that I would like to know more about the footswitch internals but came across this which may help with intermittent issues. It repositions the ground tab on the female DIN connector of the footswitch. I will have to try this and see if it helps me with issues I have.

http://www.dirtyhurricane.com/gear/Mesa_FTSW_FIX.pdf

 

[Jiveman]

Thanks for all your help. No need to crack open your footswitch, but thanks for even thinking that. I guess it makes me feel a little better if the problem is in the footswitch, and not the amp itself.

I'm going to try and get an 8-pin DIN cable, just 'cause I need that anyways, and maybe it will solve this issue (I doubt it). In the meantime, I can try bending the grounding connector, but I also doubt that would fix this problem, too.

 

[bandit2013]

I have to mod my footswitch with this trick as well.

Process of elimination helps to debug the problem. I had my footswitch apart a while back, similar issues. I re-soldered many of the pads that I could reach. I was unable to remove the PCB completely so access was difficult.

The footswitch controller must use a 4 to 2 line encoder circuit for the channel selection (similar circuit could be used with the Road King and Roadster) The rest are toggle switches which are not momentary push buttons like the channel switches. Since the LED's are tracking the channel selection, it could still be the encoder circuit but more than likely one of the two wires has a poor connection. Since CH1 is set as default, (the latches for each channel may power up in a tri-state condition may explain why all channel LED's come on when you frirst turn on the amp, tri-state output tends to drive gates on MOS or CMOS chips. If a new cable fixes the problem, great. At least that will cost effective than replacing the footswitch.

I hope you get a resolve on your issue.

 

[Jiveman]

Is the footswitch covered by the 5-yr warranty that comes with the amp? If so, I may take it in to get fixed, if the cable doesn't take care of it.

 

[bandit2013]

That I could not tell you. Not really sure what is and what is not covered. I guess I should read it.

 

[Jiveman]

Got an 8-pin footswitch cable. No difference (except that I can now finally turn the FX on/off due to the 8th pin). But the behavior with buttons/channels 1 and 2 is the same. I'll have to call Mesa next. :-(

 

[bandit2013]

that is a bummer.

Have you tried rotating the channel selection knob on the back of the amp a few times? It is possible the contacts of the switch need to be cleaned, switch usually will self clean the contact surface when moved to a different position to due wiping action. I would definitely try rotating the channel select switch back and forth a few times. I had to do this with the effects assign loop as I could not get it to work until I did this. Always kept it on footswitch position. After rotating back and forth it fixed the issue I was having.

Oh on the footswitch jack (amp and footswitch control) the ground tab was already in its proper place).

Good luck with the footswitch problem.

 

[Jiveman]

Well, went to a friend who also has a Mark V and tried swapping things around to see if I can determine if it's the footswitch, cable, or amp itself. Of course, it had to be the amp. His footswitch on my amp produces the same problem. My footswitch on his works fine. Cables don't change anything.

So, Mesa authorized repair it is. Thankfully, it's still under warranty.

 

[Jiveman]

Took it to an authorized Mesa repair, and between them and Mesa, they decided that it must get shipped to the mothership for this repair. :-( I might be responsible for shipping one-way, but then the rest should be covered under warranty. Hope everything turns out well. Will report results, when I have them.

 

[Jiveman]

Just got my amp back today, after it spent a couple of weeks at Mesa (plus some time shipping back and forth from Boston to Petaluma and back, etc.), and I'm happy to report that the problem has been identified and fixed! According to Mesa, it was a faulty footswitch input chip LM3914N (this is on the amp itself, to be clear).

Tried it for a bit tonight, and everything appears to be great with channel footswitching! It was a bit late, so I couldn't crank it in my apartment, but first chance I get, I will (been missing it, man!).

Well, there ya go. Hopefully one day, this thread will be helpful to someone else, as well.

Oh, and forgot to say: THANK YOU Mesa for great customer service! Very responsive on email and attentive to detail!