[joebog1]

As far as the oscillation goes in the amp, it sounds like you don't have the input grid tied down and the amp is using the output impedance of the oscillator as a "grid leak". It will probably raise a discussion BUT:

I start at the input stage and plug valves in and check all is well and operation of that particular stage is "as expected". Sometimes it's your layout that is flawed and not the circuit at all. I did notice that your "box/cabinet" is jam packed and that's NOT good in a high gain amplifier. Ideally, when one looks inside an amplifier, you should almost "see" the circuit in the layout, especially if the design uses "English" style circuit drawings.

A circuit diagram has a very logical and progressive design. It shows the input stage on the very left, the phase splitter (or extra voltage amplifiers) in the approximate middle and the output stage (and sometimes the power supply) and output transformer on the right. I always try and set up the chassis in just the same fashion: input on the left and output on the right of my bench. After making umpteen dozen amps for Hi-Fi I try and follow this convention. On a circuit diagram the components are placed vertically or horizontally, there are not any "diagonal bits". Very rarely do circuits cross over each other, by which I mean a plate resistor is far away from the input grid, in fact the grid is on the "bottom" of the valve with any grid leak going directly vertically down to earth, and any series resistor or capacitor from the previous stage is usually drawn horizontally from the left and the plate resistor going vertically up to the supply rail, and any coupling caps will be drawn horizontally to the right. So if you half close your eyes, its an almost straight line for your signal from left to right. JUST as we read a circuit diagram.

I hope Im not preaching to a master at all, but rather you check your layout for logical progression. Sometimes an amp of mine will not work correctly, I leave it on a shelf for a week and don't think about it at all. I then put the amp back on the bench and lo and behold I have made a whopper somewhere, thinking to save a couple of inches of wire.
I then use an extra six inches and the wire that was causing the feedback coupling disappears.

Keep up the good work
best regards
Joe