Studio Technologies ISS - Manual (Page 40)

ISS User Guide Issue 3, June 1990
Studio Technologies, Inc. Page 41
ISS
4) Raise generator level 20dB. Observe
level at TP1.
5) Reduce generator output level 20dB.
Observe level at TP1. It should drop 20
±0.3dB. If not, again adjust R56 to get
this condition.
Adjusting the Transient Response of the
Expander
1) Adjust generator frequency to 1kHz.
Adjust level to give 0dBu when mea-
sured at TP3. Set the generator to tone
burst mode: two cycles open, 64 cycles
closed. In this way, two cycles of audio
pass to the ISS, then 64 cycles of no
audio, etc.
2) Observe TP1 on the oscilloscope.
Adjust R4 to give the flattest base band
signal. The signal should not over or
under shoot.
The Band Dip Filter Returns
1) Turn mains power to OFF.
2) Remove the Type II Card from the
extender.
3) Remove the test clip linking the two test
points.
4) Reinsert integrated circuit U9.
5) This ends the procedure.
Aligning the I/O Card
The I/O Card provides a balanced output. A
positive excursion on the audio high lead
should be matched in negative amplitude
on the audio low lead. How closely these
excursions match in amplitude is called AC
balance. These excursions are referenced
to signal ground. The I/O Card contains two
potentiometers. These are set to provide
the AC balance. One pot is set for each of
the two channels.
Materials Required for Alignment
• ISS Extender Card System (two cards
and two cables)
• Low Distortion Audio Signal (Sine Wave)
Generator
• Audio Voltmeter with high input
impedance (AC VTVM), quantity of 2
• DC Voltmeter, high input impedance type
• Test Probes for above
Procedure
1) Place the I/O Card onto the Extender
Card System. Refer to the ISS Techni-
cal Manual for Extender Card installa-
tion details.
2) Turn the ISS mains power on.
3) Set the ISS to: I/O Normal, mode to
MAN, BYPASS.
4) If your facility uses resistive loading of
audio outputs, load the ISS left and
right line outputs with your standard
load, e.g., 150 ohms, 600 ohms, etc.
5) Connect the signal generator output to
the ISS left channel line input, located
on the back of the ISS.
6) Set the signal generator output to 1kHz,
with level set to your nominal operating
level, e.g., +4dBu
Checking the Power Supply Voltages
With the DC voltmeter common lead con-
nected to COM test point: check +18 test
point for +18 ±1Vdc, –18 test point for –18
±1Vdc.