Mark IV Reverb Issue

[CudBucket]

Just noticed that on channel 3 of the IV I just picked up that on the treble strings, it sounds as if the note is fretting out. Like a metallic sound from a low action. But the strings aren't buzzing at all. It's not happening on the guitar and being picked up by the amp. I don't hear on the channel 1 or 2 though. I've tried 2 guitars and 2 cabs. Happens in all cases.

The head is immaculate and appears to have stock tubes. So what's the consensus? Check preamp tubes first?

Dave

 

[Restless Rocks]

Yes check the tubes first. Wiggle the tube gently in the sockets a little and see if you hear noise. If a IVa swap V3 first as it is the lead channel tube. If a IVb both V3 and V4 are shared by the reverb and lead channel. If that doesn't get it then carefully check the tone controls of the lead channel for looseness. Rotate them several times especially the treble and the lead presence as well. These are often damaged by getting banged on doors and soforth. If you hear any crackling when you turn them try a good contact cleaner/lube. This may or may not be the problem but could help you narrow down the decision to take it to a tech.

 

[CudBucket]

Yes check the tubes first. Wiggle the tube gently in the sockets a little and see if you hear noise. If a IVa swap V3 first as it is the lead channel tube. If a IVb both V3 and V4 are shared by the reverb and lead channel. If that doesn't get it then carefully check the tone controls of the lead channel for looseness. Rotate them several times especially the treble and the lead presence as well. These are often damaged by getting banged on doors and soforth. If you hear any crackling when you turn them try a good contact cleaner/lube. This may or may not be the problem but could help you narrow down the decision to take it to a tech.

Interesting. I think I've located the issue. I did a number of things. I removed my Boss DD-20 from the loop. Turned the loop off. Tried the different modes. As soon as I turned the Reverb to 0, the issue went away. The more reverb I through into the signal, the more I heard it. Looks like I may need to change V3 and/or V4.

Thanks!

Dave

 

[Restless Rocks]

Open up your reverb tank and check that all the springs are connected on the little hooks at the transducers.

 

[CudBucket]

Open up your reverb tank and check that all the springs are connected on the little hooks at the transducers.

That's the next step. I just tried 2 new Mesa preamp tubes in V3 and V4 with no improvement. The amp had a loose fan when it got here so it's possible the tank took a jolt.

Dave

 

[CudBucket]

Wierd. I opened the tank and everything looks ok. Still, when I use the reverb, I get that wierd sound. Gonna call Mesa tomorrow.