Studio Technologies Gen II - Manual (Page 14)

Issue 3, July 1991 Generation II User Guide
Page 16 Studio Technologies, Inc.
Power Supplies
The first step in troubleshooting the
Generation II is to remove the top cover
(two Phillips head screws on each side
panel). It is common for failures associated
with contemporary audio equipment to be
power-supply related. The components
most likely to fail in the power supply are
the 3-terminal regulators (one each for +15
and
–
15) and the large filter capacitors.
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.
Analog Problems
If the power supplies are not at fault, use
standard troubleshooting procedures to
locate the problem. A simple technique is to
connect an audio signal to the line input and
trace the signal (again, using the schematic)
until the source of the problem is found.
Alignment
Alignment is required after any repair in-
volving the compandor, BBD, or associated
circuitry. Alignment is not required after
repairs are made to the line input, band-
reject filter, summing/gain, difference/gain,
meter, or line driver circuits. The following
paragraphs will aid in aligning the circuits,
which will restore proper operation. It is
important to perform the alignment proce-
dures whenever you have replaced any
components in the aforementioned circuits.
Alignment can be tricky and, if possible,
factory repair and realignment is recom-
mended.
Caution: DO NOT attempt to adjust any of
the trim pots inside the unit before you
understand the entire alignment procedure
and are equipped to go through the entire
process.
All signal measurements are made in refer-
ence to test point COM. This test point is
common to the +15,
–
15V, and
–
22Vdc
power supplies, pin 1 of the three connec-
tors, chassis ground, and earth ground via
the power cord.
Procedure
1) Apply power to the Generation II. Be
Very Careful: High voltage is present
in the power entry area.
2) On the Generation II’s front panel: set
the mode switch to the music mode,
and the stereo intensity control to the
fully counterclockwise (min) position.
3) On the Generation II’s circuit board: set
the system status switch to the front
panel mode, input level switch to 0,
output level switch to 0, and input trim
pot R1 (accessible via the back panel)
to 50 percent the (middle) position.
4) Connect the signal generator output to
the line input, located on the back
panel.
5) Set the signal generator frequency to
1kHz, with output level to OFF so that
no signal is getting sent to the line input.
The signal generator signal must be a
sine wave.
Initial Compandor Adjustments
1) Again, ensure that no audio is coming
into the unit.