The practice test was negative. My mistake: My tuner tunes to antenna voltage, no control of adaptation to the PA. This caused the PA to overload, causing the MPS2907 to burn. Repair ok. Change tuner is in progress.
I use follow regulator https://www.ebay.de/itm/Mini-DC-DC-4V-12-24V-To-5V-3A-Adjustable-Step-Down-Power-Module-Buck-Converter/272694825804
In my overvoltage-protection the 0,47µ - C is reduced to 10nF
There is a unknown problem on my QCX: Full QSK works fine, Semi QSK not - no intermission between the characters (version 1.00e)