Hi all,   
      
   I posted before while I was fixing up a couple of Quad II amps. After working   
   fine for a number of weeks, one of them just started oscillating like mad   
   before I even could put on a record. The "starting up a harley davidson"-type   
   of oscillation, ending    
   with a squeal when I shut it off. Now, the circuit is almost original, but a   
   lot of things and wires have been resoldered and I have replaced the OPT with   
   another original one, which I strapped for 9 ohms.   
   Swapping out all the tubes for known good ones did not help.   
      
   Last time I checked, all the original resistors were ok and less than 10% from   
   spec. I have raised the shared cathode R to 220 ohms to be able to run 6L6GC.   
   The C's are all renewed: C1 is a Wima pp, C2/C3 are NOS Good-All glass sealed   
   PIO with metal case,   
    C4/C6 are replaced with modern 105C 33 and 47uf. C5 is also modern, but   
   raised to 100uF/100v.    
      
   I know I will soon have to fire up the scope and do my own work, but have any   
   of you had this happen before? Is the most likely cause a bad solder joint, or   
   something like a shorted resistor in the global negative feedback loop?   
      
   Thanks!   
   Martin   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)