Topward 6603A Linear Power Supply Teardown

[anton74]

OK, an update:
I connected the external PS to the display board, to supply it stable 5V. No fluctuations of voltage were observed.  So, I replaced the 7805 and diode bridge since they could fail under load.  Still, the fluctuations are present.  Finally, I replaced the 100uF capacitor with a new one, even larger capacitor (1000 uF) and that fixed the fluctuations.  Thank you!