ASP8120-issue / 2021.03.19

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C43 worn out

Test-Condition: full load (3R5 @ +18V and -18V)

+18V POWER UP
+18V POWERUP OSCILLATION
+18V POWERUP OSCILLATION / almost finished
+18V Dropout / every half an hour
+18V Dropout and Overshoot (A)
Zomm of prev pix (A)
Zomm of prev pix (A)
-18V POWERUP (best case scenario)
-18V POWERUP (worst case scenario) (B)
Zomm of prev pix (B)
( -18V Dropout )
-18V SHUTDOWN (C)
Zomm of prev pix (C)
Zomm of prev pix (C)

both rails -> oscillation “in sync”…

BOTH RAILS – SHUTDOWN
BOTH RAILS STARTUP
BOTH RAILS STARTUP

after replacing 3x TL072 it looks symmetric…

AC measurements / both rails (occuring every few minutes or so)

after replacing Transistors on negative supply rail:

after replacing Transistors on positive supply rail: