Need Mark IV tech help

[Cameronhimself]

So today I fired up the old Mark IVA and all of a sudden, the LED's get dim on the footswitch and I stop getting sound from the guitar. I also notice that the LED's on the amp itself are no longer lit. I can no longer switch channels on the footswitch; the Loop and EQ switches work, but the LED's are dim. The tubes light up like normal, the preamp tubes look fine, the fuse is intact, but no dice. Everything starts up like normal, except no LED's and no guitar sound. I can still hear the normal amp hum, but nothing else. Any ideas?

 

[avi8r2005]

Check to make sure your loop isnt engaged with nothing in it. Also check your switching on the back to verify set to footswitch. Check all the somple things first, more often than not its the dumb little things that get us. Also check the amps function without the footswitch to check funtionality.

 

[Cameronhimself]

Check to make sure your loop isnt engaged with nothing in it. Also check your switching on the back to verify set to footswitch. Check all the somple things first, more often than not its the dumb little things that get us. Also check the amps function without the footswitch to check funtionality.

Thanks but yep, did all that and no dice. I plugged straight in; nothing.

 

[cradlefish]

It's likely the solder maybe loosen up on contact over the years of being hot when it's running.

I have the same issue. What I did was lightly tap or wiggle the led and it should illuminate nice and bright again. You'll have to do this often until you resolder it.

 

[Big Block]

I blew out the footswitch circiut on my Mark IV and it had the same exact symptoms. Better take it in.