JVC BR-S822U doesn`t load tape, LED indications is missing
 

Hi all! Happy New 2022 Year!) Anybody please help me to find a way to repaire my JVC broadcast recorder!) I bought a used BR-S822U for my studio to digitize old VHS cassettes. There were no traces of previous repairs, owner told me that the unit got stuck while loading a cassette and has since stopped working above 1 year ago. Now it does not try to accept the cassette, and the LED indication on the front panel is missing or random (there is also a black screen on the TV-out without any symbols, it looks like a reboot occurs every few seconds and the system does not booting till to error code indication). Also, 2 seconds after turning on the power, the TU motor starts twitching cyclically. Nothing else happens (The same situation if I removed all the boards available from above, except FUSE board). It looks like the main board is in some kind of peripheral polling cycle, but does not come out of it. I pressed the "reset tape counter" and "eject tape" keys combination at power-up according Service Manual - nothing changes. There is another interesting observation: when I remove the main SYSCON board and turn "on" the SW1.1 on M.CTRL/RSY board ("Load end stop mode, Reel FG duty adjustment mode", p119 of ServiceManual), the mechanism starts sequence of loading the tape (this is without any cassette) until the pinch roller is close to the Capstan shaft, the TU and SP reels start to rotate in the correct directions, but the Capstan and Drum motors do not start. Is this correct behavior or not? :question: Now I have no idea where the problems are localized - on the SYSCON board (ROM or peripheral ports), but maybe in the MechanControl Reel or Drum/Capstan control boards. All values of power voltage and fuses are good, also as all of IC stabilizators on boards too. Optical sensor for cassette door is work. I havn`t second similar device for checking modules:hmm: I will be glad to advice on tactics for localizing the problem!
Some photos of this perfect SVHS device) http://barrys8trackrepair.com/BR-S822Upics.html