I have a manley 250 amp. Uses 10 el34's in output stage. individual trim bias, and a master bias supply adjustment. All tubes check out and are matched (by me on a calibrated Mercury 2000 and bias probe). Amp has a soft start feature that warms up the circuits using about 10% power. Problem is that tube number 5 goes into over bias condition then the HT voltage fuse blows. In soft start mode, #5 runs at about .200MV where it should be around .065MV as it used to do and the other tubes still do. If I put the amp in operate mode, full power, the bias for #5 climbs till the HT fuse blows. Tube test fine. Moving tubes to a second amp does not move the problem. question is if the 33ohm resistor indicated in the bias circuit burned out to an open condition, would it cause this. I don't think it's the individual trim bias since in softsart mode, the bias trim range does alter the bias for #5. But it's basically a few hundred MV off. If I pull tube #5 and it's partner tube #10, the amp runs fine, bias is good for all remaining 8 tubes, fuses do not pop. Again, the tubes are fine. I have plent of new tubes to use to diagnose, as well as being able to test #5 and have tube #5 perform normal in my second Manley amp. I'm attaching the bias area of the schematic. Over the week end I'll pull the amp out of the rack, and test the individual components in the circuit of tube #5.