I don't understand what's happening here

[ServiceBob]

I did reverse them "for the fun of it" to no avail. No difference.

I put it all back as I found it and gave it back to my friend.

I guess the "gimmick" is the answer I will have to go with.

Thanks for y'all's input.

[rooster]

OK, what I want to know is who came up with the idea (and solution) to add the coil of wire? The guy's certainly a genius, we need him to join the forum and start solving some amp problems....

[Stevem]

I came upon a similar thing in one of my first Mesa amps I was working on and found out why it was there.

This amp ( and all of this model Mesa amps) had a white wire coming off the plate of a preamp tube gain stage, and this wire was then rapped 3 times around the grid wire for that gain.

I said to myself when a saw this that someone must of been playing games at the factory when this amp was made so I removed the wire, finished the repair that I was making and fired up the amp while looking at the output wave form.

In doing that a saw very clearly that the amp was now oscillating when it was not before, and nothing I did repair wise could have caused that other then removing that wire.

When I reinstalled that wire the oscillating problem was gone!

With that wire Mesa was curing a oscillating problem with reverse feedback, and yes this crutch of a fix that they implemented is also why this model Mesa has such a mid heavy honky tone to it, since that reverse feedback fix also acts to cut high end responce.

[martin manning]

I came upon a similar thing in one of my first Mesa amps I was working on and found out why it was there...

Clearly a negative feedback loop, via the capacitive coupling of the wire wraps on the grid lead. That sort of thing is not uncommon in RF circuits, as mentioned above. The remote coil in the amp in this thread is something different.

[rooster]

Yep, I've seen this in a Mesa amp, too. But as I recall, the wire went to a different tube? Maybe reverb circuit or maybe your recollection is better than mine. In fact, it might have gone as far as the output section? But it was a long wire in the amp I saw, not something that attached to the first preamp tube.

[Stevem]

My mind is not 100% sure it, it may have gone to the grid of a different tube like you recall, but I think it stayed in the preamp section and did not go into the output stage.
Once again though I am not 100% certain.