HamCall (October 1991)/HamCall (Whitehall Publishing)(1991).bin/bcast/audvid/mtr90fix.txt

Text File | 1990-10-14 | 2KB | 33 lines

The capstan and tachometer rollers on the Otari MTR-90 can
develop a problem that you will swear is caused by your
synchronizer or by an adjustment on the tape machine itself.
The symptom of the problem is an uneven rewind or fast forward.
The tape tension arms will slap against their stops and be quite
noisy about it also.  Sometimes the machine will jerk for just an
instant in play mode as well.
What has happened at this point in your machine's life is the
big brown rollers have become glazed and the tape is actually
slipping against them.  Since the 90's drive system is a closed
loop servo, any slipping between rollers and tape causes error
to be introduced instantly into the system.  The servos then try
(as all good servos do) to compensate for this error by quickly
changing speed.
Barry Ross at Otari service says to prevent slippage in the tape
path, clean the brown rollers with 98% isopropyl alcohol (not the
watered down 72% version at drug stores.)  If your rollers are
too far gone to be cleaned, simply replace them.  Barry also
says the glazing is accelerated by using the machine with
synchronizers.  I've changed the rollers on the one here at
Alpha Audio and the difference is remarkable.  You can crank up
the wind speed so that the MTR-90 winds just about as fast as a
Studer 24tk.  And it handles 14" reels like they were toys,
giving me a lock-up time of less than one second.
So now armed with this information, I hope you won't be fooled by
glazed rollers.
Oh, one other thing that maybe everybody doesn't know.  The
cooling fan on the MTR-90 has two speed settings (60Hz and
50Hz).  The switch is available behind one of the side panels.
The 50Hz setting quiets the machine down substantially and
doesn't seem to affect the cooling at all.
Good luck.  I hope this information is useful to you.
Joe Sheets, Chief Engineer, Alpha Audio, Richmond, VA.