INTERNAL SYNCHRONIZER (OPTIONAL ACCESSORY QSLI)
This device has two functions:
A)
It measures the amplitude of the playback pilot signal on the tape. With the meter
switch in the position "Pilot Playback" the meter indicates the amplitude. The
normal value should be between 1 and 2 V on the lower middle scale.
B)
It can modify the tape speed of the Nagra in order to render the playback pilot
signal synchronous with a pilot signal coming in on the "Pilot" socket on the right
side. For this speed correction to take place, the Nagra must be switched to
"Loudspeaker Playback" and the "Pilot" indicator should show a white cross. The
white cross is only shown if the external pilot reference signal is correct and a pilot
signal is played back from the tape.
When the meter switch (12) is in the "SYNCH" position, the meter is connected to the QSLI, and
shows the difference of phase between the external pilot signal and the playback pilot signal from
the tape. Thus, if the signals do not have exactly the same frequency and phase the needle will
oscillate. This can be seen on "Playback" (without the loudspeaker). One complete oscillation left,
right, left, every 2 seconds corresponds to a speed error of 1%, which can be corrected by the
QSLI.
By putting the main function selector in the (Loudspeaker Playback) position the QLSI is switched
on, and the needle should be stationary. If it continues to oscillate, then the frequency exceeds the
synchronizing capacity of the QSLI. If the Nagra is equipped with frequency meter circuit QFM, and
the needle is stationary and if the pilot indicator shows a white cross, synchronization is practically
certain.
There is one exception, however, if the playback frequency from the tape is grossly incorrect (e.g.
100 Hz instead of 50), the needle will not be able to follow the beat and will remain stationary in the
center of the dial.
If this is suspected, switch to Playback. The needle should oscillate. If need be, upset the tape
speed by blocking the left hand tension roller momentarily. If the needle remains in the center, the
recorded pilot signal is incorrect.
The speed varier QSV-2 is very useful in these cases. In attempting to adjust the speed (on slaved
playback) the QSLI has to adjust itself in order to prevent the speed varier from operating. The
needle of the meter will show this adjustment and will prove that synchronization is correct.
SPEED VARIER QSV-2
This is an external accessory for the Nagra 4.2. It is plugged into the ACC socket (39) on the left
hand side of the recorder. It enables the speed to be varied manually up to ±12%. The QSV-2 is
used for the following applications:
A)
To transfer a tape whose pilot signal originated from a camera whose speed was
out of tolerance.
The QSLI synchronizer allows the automatic correction of speed errors up to ±2%.
It is not unknown for cameras to have a speed error greater than this tolerance.
The speed Varier allows the offsetting of the average speed, which will then be
corrected by the Synchronizer in the normal manner. Naturally, under these
conditions, the tone of the sound will be altered, but this is inevitable.
B)
Transfer of a tape whose pilot signal is interrupted. A very convenient method of
indicating the start marks (or end of takes) as well as the take identification is by
short interruptions of the pilot signal. During these interruptions, the slaving
between the Nagra 4.2 and the film recorder is suppressed. It is important that the
speed change during the suppression is not brutal, otherwise audible wow will be
heard. To avoid this, it is sufficient to make approximate correction with the aid of
