Studio Technologies ISS - Manual (Page 39)

Issue 3, June 1990 ISS User Guide
Page 40 Studio Technologies, Inc.
ISS
6) Connect the signal generator output to
the ISS left channel line input, located
on the back of the ISS.
7) Set the signal generator frequency to
1kHz, with output level to OFF so that
no signal is getting sent to the ISS left
line input. The signal generator signal
must be a sine wave.
Checking the Power Supply Voltages
With the DC voltmeter common lead con-
nected to COM test point: check +15 test
point for +15 ±1Vdc, –15 test point for
–15 ±1Vdc.
Checking for the Correct Rough Setting
of the Compander
1) Again insure that no audio is coming
into the ISS.
2) With DC voltmeter common lead con-
nected to COM test point: check TP5
for 1.35 ±0.3Vdc. If not within this
range, set R69 to give 1.35Vdc at TP5.
3) With DC voltmeter common lead con-
nected to COM test point: check TP7
for 1.35 ±0.3Vdc. If not within this
range, set R56 to give 1.35Vdc at TP7.
Setting the Analog Delay Clock
Frequency
1) Connect common lead of frequency
counter to COM test point. Check TP2
for 64kHz ±0.5kHz. If not within this
range, set R20 to give a value in this
range.
Adjusting the Incoming Audio Test
Signal
1) Connect the AC voltmeter common
lead to the COM test point.
2) Adjust audio generator output level to
give –10dBu reading at TP3.
Adjusting the Compressor
1) Move AC voltmeter lead to test point
TP4. Note the reading that you observe.
It should be –10 ±2.5dBu.
2) Reduce generator output level 20dB.
3) Observe level at TP4. It should have
dropped 15 ±0.3dB. If not, adjust R69
to get this condition.
4) Raise generator level 20dB. Observe
level at TP4.
5) Reduce generator output level 20dB.
Observe level at TP4. It should drop 15
±0.3dB. If not, again adjust R69 to get
this condition.
Adjusting the Analog Delay for Minimum
Distortion
1) Adjust generator frequency to 5kHz.
Set level to give –10dBu when mea-
sured at TP3.
2) Connect distortion analyzer to measure
at TP1.
3) Adjust R18 to give minimum distortion
(THD + Noise). The acceptable mini-
mum distortion is 0.35% or lower. The
usual minimum is 0.25% to 0.10%.
Adjusting the Expander
1) Adjust generator frequency to 1kHz.
Set level to give –10dBu at TP3.
2) Measure level at TP1.
3) Drop generator level 20dB. Level at TP1
should drop 20 ±0.3dB. Adjust R56 to
get this condition.