Operating instructions

4. When a wideband reader synchronizer is used, it is necessary for the
MTR-90 to reproduce the complex waveforms of the SMPTE code at 10
or 20 times normal play speed. To enable the MTR-90II to reproduce
time code accurately at these speeds one of the following changes must
be made:
A. The WBR-1S is a piggyback PCB attached to an audio channel PCB.
This modification must be done by Otari, and is available installed
on either a new or your existing audio PCB. The WBR-1S can also
serve as a normal Audio channel PCB (switchable) if so ordered.
The WBR-1S also includes two logic bypasses that permit it to be
free of the mute and attenuation requirements discussed in Steps 1
through 3 above. The WBR-1S features an adjustable phase trimmer
to optimize the performance of the board for the head and speed
being used.
B. Due to technical advances in SMPTE time code readers since 1982,
it is possible to modify a standard Audio PCB to be a dedicated
SMPTE code channel PCB, instead of adding a WBR-1S.
1. Install 10 kΩ resistors across both R101 and R125 on the
Audio PCB.
2. Cut the traces leading to pin 12 on the "B" side, and to pin 34 on
the "A" side of the PCB edge connector.
3. Add a wire jumper from Pin 3 of IC 105 (+ voltage) to the end
of R589 that went to the edge connector.
5. When constructing interface cables for use with the MTR-90II, care must
be taken to prevent crosstalk between the 9600 Hz signals used for
capstan speed reference. The 9600 Hz signal is sent from the MTR-90II
to the synchronizer to enable the synchronizer to loop the capstan
control signal back to the tape machine when the synchronize is put into
bypass.
The MTR-90II is equipped with an automatic reference switching circuit that,
when the tape machine is in External Reference mode, looks for a 3.5 to 5
Volt TTL FM signal with a range of 25% to 250% of 9600 Hz. If a signal
meeting both these parameters is not present, the MTR-90II will
automatically be switched to 100% crystal reference.
If there are any questions regarding these suggestions for preparing your
MTR-90II for SMPTE interface, contact your local Otari dealer, representative,
or Otari technical support.
The following information regarding interface of the MTR-90II to various
synchronizers has been provided by the synchronizer manufacturers.
MTR-90III Operation and Maintenance Manual
October 1990
Appendix A
A - 3