Ran it through google translate:
Catastrophe, my amp TSA15H is down>
At certain times, a "srach" sound appears, for 0.25 seconds, once a day or every 2 minutes !!!
In some cases, at this point, the ON / OFF indicator goes out!
Solution failure 1:
This is a component supply failure.
The 12 Volt regulator (U3 BA12T in the diagram, U201 7812 on the PCB), which powers the 12AX7 heater, is in the TO220F (Full plastic package) case, switches to thermal protection: the ON / OFF indicator turns off and the Voltage on the lamps of the preamp causes noise.
I replaced with a 7812 TO220 (with metal tab, thermally conductive paste and without insulation). Because of this, the radiator is a bit warmer ... and the 7812 a little colder ;-)
This is a manufacturing defect.
When I touch a lamp of the power amp, a 6V6, the sound "srach" appears!
I suspect a socket defect. It is one of the yellow threads, filament, whose contact is bad.
I cut the insulating sheath and I find the twisted but unwelded wire on the lug.
I clean, I weld, I place a sheath
My TSA15H finally works like a new one: dbtu:
Good work !!!