# SOLVED: Mesa Mark IIb channel switch issue



## warplanegrey (Jan 3, 2007)

I have a 1980 mesa mark IIb That does not switch channels using the foot switch. The channels change just fine using the push pull knob, but for some reason the foot switch that does not switch channels using the foot switch. The channels change just fine using the push pull knob, but for some reason the foot switch doesn’t work. 

I have tested the foot switch and it tests fine. I’ve used different cables and they’re all fine. 

Any ideas as to where I should start looking?


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## silvertonebetty (Jan 4, 2015)

warplanegrey said:


> I have a 1980 mesa mark IIb That does not switch channels using the foot switch. The channels change just fine using the push pull knob, but for some reason the foot switch that does not switch channels using the foot switch. The channels change just fine using the push pull knob, but for some reason the foot switch doesn’t work.
> 
> I have tested the foot switch and it tests fine. I’ve used different cables and they’re all fine.
> 
> Any ideas as to where I should start looking?


Pictures ? 

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## Sneaky (Feb 14, 2006)

Is the switch LED lighting up? Are all the push/pull knobs pushed in?


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## silvertonebetty (Jan 4, 2015)

Sneaky said:


> Is the switch LED lighting up? Are all the push/pull knobs pushed in?


The only knob that needs to be pushed in is the lead


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## Sneaky (Feb 14, 2006)

I think all five are supposed to be pushed in. Also, make sure you are using a mono cable for the switch, not Stereo.


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## silvertonebetty (Jan 4, 2015)

Sneaky said:


> I think all five are supposed to be pushed in. Also, make sure you are using a mono cable for the switch, not Stereo.


Lol I know because I own one










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## Sneaky (Feb 14, 2006)

In the manual it also says make sure all five switches are pushed in. I think the idea being that the pull switches aren’t required eg. treble shift is automatically engaged in lead mode, etc. Now I have a Mk III, so you obviously know more than I do about the IIB.


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## silvertonebetty (Jan 4, 2015)

Sneaky said:


> In the manual it also says make sure all five switches are pushed in. I think the idea being that the pull switches aren’t required eg. treble shift is automatically engaged in lead mode, etc. Now I have a Mk III, so you obviously know more than I do about the IIB.


O ok lol i do agree with the cable .ive heard that for cabnets to heads and stuff

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## warplanegrey (Jan 3, 2007)

Sneaky said:


> Is the switch LED lighting up? Are all the push/pull knobs pushed in?


Yep. Lights up fine.


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## warplanegrey (Jan 3, 2007)

Oh okay so all have to be in? I’ll check that.


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## keto (May 23, 2006)

Possibly the jack?


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## jb welder (Sep 14, 2010)

schematic: http://www.freeinfosociety.com/media/images/4137.gif
Footswitch stuff at the bottom.


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## warplanegrey (Jan 3, 2007)

All knobs pushed in. No joy.


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## silvertonebetty (Jan 4, 2015)

warplanegrey said:


> All knobs pushed in. No joy.


Try another cable


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## warplanegrey (Jan 3, 2007)

Different cable, no joy


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## silvertonebetty (Jan 4, 2015)

warplanegrey said:


> Different cable, no joy


No fun . Could it be a bad cap or tube 


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## dtsaudio (Apr 15, 2009)

Might be a bad relay. Can you hear the relay trip?


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## warplanegrey (Jan 3, 2007)

No, silence from the amp. Stuck on clean. 

But yeah, I’m able to use the push/pull to change channels no problem.


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## dtsaudio (Apr 15, 2009)

I think the relay contacts parallel the pull switch, which is why the switch needs to be in to use the foot switch.
A bad relay, or connection to the relay would explain it. That's at least the area you need to concentrate on.


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## nonreverb (Sep 19, 2006)

I concur. Looking at the schematic, it's the most logical place to check.


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## danielSunn0))) (Dec 28, 2015)

I own a mkIIb and a mkIII and I've had troubles with the relays. I was talking to my tech about it the last time I had to bring the mkIIb in and he was telling me about how one of the weakest designs in the earlier mk series is the relays, and they can cause a series of issues. Something to do with using relays that are underpowered to handle the current that goes through them long term. Layman's terms as I don't know enough to go into detail personally.
The mkIII had switching issues because a relay got sticky, and the other one cooked a relay and it would blow a fuse every time I brought it above bedroom volumes or added substantial gain. Both work like a charm now and have seen plenty of use!


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## warplanegrey (Jan 3, 2007)

Turns out I had a few bad cables. I’m le stupid.


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## danielSunn0))) (Dec 28, 2015)

Glad to hear you solved it, and that it was a rather easy fix at that!


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