To G?ran:
OK, shorted pin 13 to ground. Still same result: the SMPS refuses to starts and ticks herratically.
I've checked the signal across A and K of Q30 (the PUT): it fires up every 20 msec (I live in Italy) but there are some spurious pulses in between.
The pin 9 shows a steady +0.6V with sparse negative pulses going to approx 0 V.
To Albert:
I really don't know how a dummy load must be connected to raw outputs! Some people told me to load +17V was sufficient, some others the +108, now you and others say that the load MUST be distributed across the raw outputs! I'm really confused now...
And yes, I've disconnected the supply to HV unit obviously... since the SMPS block sits on my workbench, alone.
Some times ago (several months ago I suppose), a friend of mine fixed a 7904 SMPS; he told me that as a load he had connected a 20 ohm resistor on the +15 (regulated output) and nothing else and the smps worked ...
