When you get a quick blast of sound then dead set its usually high voltage
shut down ( HVSD ). Caused usually by the main power supply putting out too
much voltage, failure of HVSD circuit, OR a heavy load on the HV circuit.
If you have a variac & AC amps meter we can help with it.
ALSO post a few "nudies" of the chassis, it connects better than anything
to our minds........
73 Zeno
LFOD !