ZenV4 oscillations problem

[fastcross]

I have as soon as mounted a channel of the zen v4 and it seems to me that it oscillates alone (seems to me to 166Khz. "2 microsecond X cm" one complete cycle of the sinusoide occupy me 3 small checks) amplitude 10Vpp, a light lowering of the feeding tension as soon as it begins the autooscillazione. Regulating Vr4 the oscillations disappear, but on Q1 instead finding half feeding find nearly the usual value of the Vcc regulated. You could indicate something to make to me. I have already controlled cables, masses, long courts, weldings, already replaced c3 c12 q3. Q1 R0 R1 many warmth, if I insist raising the tension with the variac until 42v regulated to you, burns Q1 Q2 R0 R1 Thanks Alfei Oriano orialfei@tin.it

[MikeW]

If you have long leads coming from your main power supply caps you may need a bypass cap on the +V line right at the board. I used 220 uf. 63 volt caps.