MTR-90 MKIII transport -- bi-directional -- closed- loop -- servo system

[digitall2000]

hi

today while checking the record and erasure operations on the mtr-90  mkIII i started
havin problems again with the MDAs or some other part of the tape drive "gizmos"

after going through hell trying to set the tensions, servo voltages and adjusting
feedback system as per the otari mtr-90  mkIII manual plimousse turned me
onto a document by steven smulian on the proper way to setup the
" MTR-90 MKIII transport bi-directional , closed- loop servo system "
and the machine came to life and had been running smoothly

today the machine was consistently, when in rewind mode, popping the
- 40V  breaker on PSU and pretty slow to start up into play mode (2-3 sec.)

if when in stop mode,  i pull the supply swing arm forward slightly the machine
starts rewinding the tape slowly and gradually speeds up the rewinding over time
and none of the transport controls have any affect on the machine in this state
i have to push the swing arm back toward the supply reel until the tape stops

does that point to the MDAs, PSU, tension, drive gain?

also

gyraf and others have stated that if one of the transistors on the MDA is bad, to
replace them all, all on the board that tests bad or all on all the boards?
what about the smaller driver transistors and the diodes?
does anyone know the equivalents for these?

thanks for all yer help so far
and for any future help and advise

lance

 

[NadMk]

If it has a weird behavior would point to the Logic Transport.
I don't find any reason to replace all IC's if there is just one faulty.