Mark IV - Strange Footswitch LED Issue

[GD_NC]

The Loop LED on my footswitch will not turn completely off. It toggles between ON/DIM instead of ON/OFF.

The Loop LED on the amp is fine and the loop is switching in and out correctly. I just cant get the LED to turn all the way off on the footcontroller.

I've checked all the obvious stuff cables/connections and looked inside the foot controller and don't see anything wrong. It's especially annoying because I just got the amp back from having it serviced. It worked perfectly for a week then this issue crops up.

Any ideas what might cause this? Anybody else had this problem with their Mark IV?

 

[Boogiebabies]

Tap it with your fingernail. The LED's on these amps seem to get stuck once in a while.

 

[Restless Rocks]

The loop and EQ switches are latching types as opposed to the momentary contact used for the channel switching functions. First thing to check would be if the switch is completely opening the circuit when in the off position. When these switches go bad replacement is usually the only recourse as it's very difficult to clean them like you would a pot. Also this doesn't completely rule out the possibility of a bad voltage regulator in the circuit. It's very difficult to diagnose these things when the item is not physically on the bench in front of me.

 

[GD_NC]

The loop and EQ switches are latching types as opposed to the momentary contact used for the channel switching functions. First thing to check would be if the switch is completely opening the circuit when in the off position. When these switches go bad replacement is usually the only recourse as it's very difficult to clean them like you would a pot. Also this doesn't completely rule out the possibility of a bad voltage regulator in the circuit. It's very difficult to diagnose these things when the item is not physically on the bench in front of me.

How do I check the switch? It appears to work correctly. The loop light on the amp works and the loop turns on/off as it should. Can I verify it with a muti-meter somehow?

 

[GD_NC]

Tap it with your fingernail. The LED's on these amps seem to get stuck once in a while.

Thanks for the reply!

That was my first thought too. This amp has a bad R2 LED (now fixed) that required an occasional thump. I've checked, thumped and wiggled the obvious stuff: Plug, cable, LED, flipped the Loop assignment switch a few times etc...

 

[bryan_kilco]

are you sure your FX Loop is set to OFF on the back of the amp? I noticed, that if the switch is ON, and you try to tap the button on the footswitch, it will slightly dim the light but not go off.

I know this probably isnt the case...figured I'd ask.

also, an LED or 2 on my footswitch sink down inside the pedal sometimes. and my EQ LED on the amp itself sometimes doesnt light up, and if I tap it, bam - lights right up.

 

[GD_NC]

are you sure your FX Loop is set to OFF on the back of the amp? I noticed, that if the switch is ON, and you try to tap the button on the footswitch, it will slightly dim the light but not go off.

Yes - I checked the assignment loop switches. That does not seem to cause the problem.

also, an LED or 2 on my footswitch sink down inside the pedal sometimes. and my EQ LED on the amp itself sometimes doesnt light up, and if I tap it, bam - lights right up.

I opened the footswitch and checked the connections. All the LED's seem to be well seated and making good contact. Wiggling and pushing does not make it blink.

FWIW - It's really easy to snap your footswitch LEDs back into place. Just open the back of the footswitch. pull back the plastic sleeve around the LED, then push it back up into place, then slide the lower sleeve back up to lock it in place.

Thanks for the reply! I think I've done all the trouble shooting I can do. I going to take the amp to the M-B service center later this week and get it fixed.