a little scare last night with the Mark IV

[bryan_kilco]

so...I've been using a 5150 as my main rig lately, and my Mark IV has been sitting around the practice space. Our other guitarist asked if he could use the Mark, so I let him run it at practice last night. I didnt pay attention and later realized he was running a multi-fx processor just for the gate, after his guitar in-line. I told hime that he should run it through the FX Loop, and hooked it up for him. when I flipped the amp back on, the amp was at practice level and wasnt seeming to get the gate that we needed from his processor. with the gate in-line, the amp was noisey as all hell....hissing when on lead channel. So, I run it how he had it in the first place, turn her on and its really quiet. Tone is totally de-saturated and just shitty sounding. I was scared to death....made sure everything was connected properly and last resort I flipped it to Standby then back to ON and it worked fine.
Strange.... :?

 

[rotaryunison]

My Mark IV has been similarly intermittent with the FX Loop. Sometimes it works fine, then others, I flip it on and the volume is at about 1/10th the usual volume and tone is horrible. I'm taking it in this week for a check-up. I'll let you know what they find out.

 

[LithiumZero]

Probably just need to clean the FX loop jacks

 

[shredding]

Mine had the same trouble before when i tried to put in my vox tonelab for the effects in the loop. when I turn on the loop from the footswitch, the volume drops and all the lows are sucked away even with nothing plugged in to the effect loop.

I replaced the preamp tube that controls the effect loop and it works fine since then.

Now I'm using a Gmajor and it never has any issues. This is what I guess: the output level of the tonelab or your effect pedal is too hot (I don't really know if that's true) so it overloads the preamp tube.

 

[rotaryunison]

Mine had the same trouble before when i tried to put in my vox tonelab for the effects in the loop. when I turn on the loop from the footswitch, the volume drops and all the lows are sucked away even with nothing plugged in to the effect loop.

I replaced the preamp tube that controls the effect loop and it works fine since then.

Now I'm using a Gmajor and it never has any issues. This is what I guess: the output level of the tonelab or your effect pedal is too hot (I don't really know if that's true) so it overloads the preamp tube.

How long has the fix been working for? Which tube controls the effects loop?

I have nothing plugged into my effects loop, so I'm not sure why this would happen.