Enzo...quick update
Fr: Seeker (yamaha g100)
First off, you guys are good and thanks for everything. Long story short a guy traded me an old bogner 75 watt head for my G100 412.  Major mouse nest in it and needs lots of TLC but I think this will be a good start on the SS pre-amp with tube power amp I wanted to build. The 412 cab was a bit unpractical for my apartment anyways (according to my wife anyways lol).  But thanks again, I really enjoy watching/reading you guys in action.
Seeker

Hey Enzo
Yamaha here,

Tried the reverb thing and yes, the frizzies are still there.  I'm too tired and frustrated tonight (not having a good health week) to find the proper schematic.  I'll look tomorrow when I'm rested and hopefully feeling better, in regards to the dc voltage etc.  Thanks again.
Till later
Seeker
PS: good to narrow it down to the power amp..thanks....will remember this "trick". My amp does not have pre-out or power in...I forgot that I could use the foot switch control circuit.  One quick question...Is the distortion circuit between the pre and power amp or "in front" of the pre-amp....hmmmm I guess I will find out by looking at the schematic.

Thanks
Seeker

In addition....
I had not used this amp for over a year due to another issue...Just played it for the last hour and I lied..it really bothers me.  I think the "frizzyness/decay was even more predominant after the amp "warmed" up.
Seeker

Howdy

I too am new at ss amp repair, so I'm afraid I can not offer assistance.  However I will be interested to read the replies.  I have the same issue' I think' with my '75 Yamaha g100.  I describe it as the way the note/sound "decays" and I too thought of speaker problems but tried what you did with no effect. Volume does no effect it either.  I do not make my living with this amp and in reality it does not bother me (well just a bit).  I do wonder if it's a "precursor" to a bigger problem down the road.
Thanks for your post,
Seeker

One thing about the pots on this Fishman, unlike other pots I've worked on, is that the shaft going into the pot is smaller than the part of the shaft the nob slides over. There is a portion of the shaft (with no "splines") approx a 64th of an inch long that butts up tight against the threaded part of the pot. These two parts have the same diameter. (I've never noticed this on pots before) This would make it impossible to lubricate unless it was taken apart (if it's even meant to be taken apart).  Other pots you could simply spay/drip in a lubricant.  I guess an important question to ask is.... when you clean a pot from the front (as I did) do you risk contaminating the pot with the pre-existing lubricant,  Or simply put, will it hurt it's performance?
Seeker

Howdy,
I recently cleaned the pots on my 1975 Yamaha g100 412.  I truly thought the bass pot was shorted out given the symptoms. I could not believe the results from a good cleaning..like brand new now.  So my Fishman SA 220 was having the same issues when I adjusted the treble on channel #1...the clip light even came on.  But after reading numerous post I really did not want to disassemble the amp(sounds like quite the process after reading other posts) to try cleaning the pot.  So I thought I would try the following.  I took a piece of 1/4 inch (inside diameter) clear tubing and cut off 1/2".  I unscrewed the nut holding the pot to the "face-plate".  I gently "screwed" the tubing over the treads on the pot till it tightened up (bottomed out).  I used the "factory cut" on the tube because it was a perfect 90 degrees to insure a good seal when it "bottomed out".  Then I inserted the red straw of the contact cleaner down along the side of the shaft, tightly held a piece of tissue around the top to reduce the amount of cleaner escaping  and sprayed. In between spays I rotated the shaft. After 3 good spray I checked it out...did not solve my problem.  I repeated the process two more times and wow..it finally worked. I did notice the pot feels..hmmm..."dry" compared to the other controls.  I'm assuming the cleaner removed any lubricant there may have been on the shaft and this may be the reason it took so many attempt to finally get it to work.....but it worked and I did not have to dissemble the amp.  The amp was used 20 hours in the past week and no return of the problem.  Just one word of caution...wear safety glasses...and of course read the label.  I'm building a better version of the clear tubing "tool"  It is sealed at one end and the red straw is  super glued through a small hole in the side.  This should provide more pressure, forcing the cleaner into the pot past the shaft.  Hopefully I will not need to try it out for a while.
Have a great day.   
PS:I hope my instructions were easy to decipher.

Hey...my first post.

I have an ABI (acquired brain injury).  Learning new things..well let's say it's a big learning curve for me. When learning about tube amps, besides what's recommended by individuals at sites like this (books etc) I found a guy on You Tube named "Uncle Doug" to be very informative.  Just watching him explain something when he is fixing an amps puts things in "context" for me. It's kinda an "applied knowledge" approach to what I've picked up here and there.  I'm starting to build a SS pre-amp with tube power amp like my old Peavey Classic VT series.  I've found the info people post on these sites so helpful ... so keep on postin' and thanks.
Seeker