interesting.  another forum says do not start a new thread for the same device.  different strokes folks.  the only confusion is keeping the trends straight  :loco
otherwise Im pretty good with discernment.  probably bench the amp this weekend and practice with the pot connections as small and delicate as they are on PCBs.
but knowledge of operation flow wouldnt hurt.
I see that AUTOMIX plug lifts CT GND off of Q2 base turning it ON that turns Q1 ON.
must be sending + voltage to either FS-2 or FS-3 through FS-1 to operate the CMOS switches ?  this is what is confusing to me.  the switches, CMOS and foot :loco
pretty straight forward after signal hits U5A then its OP amp to hop amp til it gets to the power amp stage.  goes through two driver/phase inverter IQ1 and IQ2.  one is getting inverted signal from OT secondary.  then 6L6GC pp output :duh

PS:  at the same time AUTOMIX Q1 ON is sending bias voltage to U2 that beefs-up the signal from U1A while U4 is OFF...

hmmm...  more thinking.  maybe Q2 is sending CT GND to FS-2 or FS-3 through Foot Switch.  U2 does the combining while foot switch connects FS-1 GND to either FS-2 or FS-3 turning each OFF/ON

still trying to figure out the foot switch with the OP amp and CMOS data.  looks like COMBINE has something missing in the foot switch diagram.  combine what.  connects pin-1 to F.S.-1 at Q2 then SELECTOR selects between pin-2 and pin-3 connecting F.S-2 or F.S.-3 at U3 and U4 CMOS.
all I can figure is that plugging into J4 AUTOMIX is always connected through J3 BRIGHT.  U4 is switched ON/OFF cutting BRIGHT amp U1A into U5A or U2 that mixes or not with NORMAL amp U1B.  U3 switches NORMAL ON/OFF.  the foot switch does this somehow while making hard connections between F.S. points.  something else U2 has pin-9.  there is no pin-9 in a CA3094 OP amp.  must should be pin-4 Vcc-

this may be helpful for anyone trying to find Peavey parts
http://www.ampix.org/albums/userpics/10003/PV_Semi_Cross_Ref.pdf
this is pretty cool op amp illustration
http://www.williamson-labs.com/480_opam.htm
I may get a chance to bench the Peavey this weekend  :dbtu:

for those interested in the ugly beast
http://www.sacmusic.de/amps/reload.html?pea_cl.html
now you know what were talkin about :dbtu:
what did I know about amps back in the day.  thought that it was longer ago than 79 but I must have just been coming out of the fog of the 70s.  a favorite gig piece borrowed frequently by a buddy locale venue musician.  the clean channel or BRIGHT in Peavey land is pretty good actually when the thing is working.  NORMAL whatever that is channel is kind of gritty by tube amp standards.  I am now learning solid state after favoring tube amps, old radios and such for so long.  hope you dont mind the dribble but I am having fun with new interests  :lmao:
still more to come  :duh

true.  discussion redundant.  thermal.  solder.  got it  :duh

might should consider loosening the face plate mounting screws in case the amp winds up on its face again.  something has to give either mounting screws or pots :dbtu:

you would think that 1.6v at U5A would not be enough to cause thermal issues at R46 pot.  but it acts thermal by nature after running normally then 'yoink' high frequency time with no MID control.  plugged guitar out/in to every input, switched foot switches, change control settings.  same thing.  turn OFF amp come back later back to normal.
BTW diagram doesnt say about the two ground symbols.  one is chassis the other is BUSS for CT at 0v

yes in tube radio world it is known as a Dim Bulb Tester.  high current is dropped across the bulb protecting your equipment instead of high current across expensive delicate components such as transformers.  you can gage the bulb size by device power consumption.  100W power consumption = 100W bulb.  not to be confused with power output which is not close to power consumption :duh

so if R46 low side is going open neither C29 or C58 is never grounded.  that might account for the highs being amplified.  funny how the amp operates normally then suddenly has failure.  let it rest it goes back to normal then operating awhile fails again.  no static no noise more like an electronic component failing.  but I have been fooled before  :loco

thanks for the input guys.  it has phase shifter with speed intensity and color control.  high speed = tremolo.  all original with square magnet speakers.  no need to change them because you can use the 4ohm 8ohm output jack to any cab you want.  I have tried different speaker cabs with some noticeable difference.  the input/output loop is a nice feature.  I did play around with both once upon a time.
shorting power supply filter capacitors will fry any resistors in the circuit.  dry shorting electrolytic capacitors = high current.  better fried resistors than output transformer.  I have used coffee filter and Elmers glue to mend speakers.  Elmers is water soluble, flexible and strong.  coffee filter paper is tuff and flexible.  repairs still going strong.
the issue with my unit is that it suddenly goes into a treble sound with the MID pot losing its control.  almost like a heat component failure.  like electronic switching.  I am thinking now that maybe one of the small electrolytic capacitors is dried-out and grounding some signal in one of the op amps.  not knowing characteristics of op amps I am only guessing.  yes it does have the original capacitors in it...   
short op amp tutorial would be great :dbtu:

yes phase shifter temolo.  different speeds different effect.  great reverb.  select and combine switches.  all in the original foot switch.  check out the schematic attached to see how they do the switching with transistors.  mine is all original.  I have a lot of tubes to swap out.  not much difference really.  everything works fine except for the MID cutting-out

greetings Enzo.  thanks for your reply.  I see that this is an active forum.  great.  new here
that should be the correct diagram VT Series.  bought amp used back in the 70s.  got the print from the factory more recently but some time ago.  factory pretty good about sending a diagram.
from memory I thought TREBLE but checking today it is the MID that suddenly has no control.  plays fine for awhile then MID quits.  no control but no scratchiness.  the sound becomes treble although there is control with BASS and TREBLE.  I would guess that the MID pot is bonkers stuck at the high side but I am not a solid state person.  I know that tone stacks are tone stacks and pots are pots but maybe something kooky unknown to me going on.  any further circuit analysis appreciated

by tone control I mean treble.  see in first section solid state
maybe R45 going short

greetings.  new to the forum.  I have an old original Peavey 212 Classic hybrid SS front end with 6L6GC output.  after playing for awhile the tone control cuts out.  jumps to a high frequency and stays there until next time after being off for awhile.  the control turns UP/DOWN but no change :loco
any thoughts
likes/dislikes this amp
whatever
I am familiar with working on tube amps, radios and some with transistor radios
first attempt at attaching schematic.  check it out