Figure 1.11. Connecting The Hookup Leads - QSC PowerLight3 Series Technical & Service Manual

1.5 PL380 Service Fixture (continued)
2. Turn off the service fixture's power switch and connect it to the
AC mains. The service fixture has a universal power supply that
can operate on any AC voltage from 100 to 240 volts.
Prepare the amplifier
3. Disconnect anything connected to the amplifier's inputs and
outputs.
4. Disconnect the amplifier from the AC mains and allow at least
five minutes for the
internal voltages to
bleed down.
5. Remove the
amplifier's bottom
cover.
6. Set the amplifier on
the test bench next
to the service
fixture, with its
Figure 1.10. Jumpers to be removed
open side up and
from Test Point B
front panel facing
you.
7. Locate the two test points on the amplifier's main circuit board.
Test Point A is located near the output board, while Test Point
B is in front of the power transformer (Figure 1.10).
8. Remove the two jumpers from Test
Point B (Figure 1.11). Set them
aside to be re-installed later.
Connect the fixture and
amplifier
9. Connect the service fixture's two
hookup leads to the corresponding
test points. Make sure you orient
the housings correctly (as shown
in Figure 1.12) when you plug
them onto the test point headers.
As the lengths of the leads
suggest, the long one goes to Test
Point A and the short one to Test
Point B .
PL3 Series Service Manual
TD-000274-00 Rev. A
Pin 1
TEST POINT B
Remove jumpers on
pins 3–4 and 5–6 before
connecting service fixture.
Replace jumpers for
normal operation.
Test Point A TEST POINT A

Figure 1.11. Connecting the hookup leads

Initial tests with the service fixture
These initial tests with the service fixture will allow you to deter-
mine whether the amplifier's clock and control circuitry are working
properly, with no risk of damaging high-power devices or circuits.
Tools and equipment needed
• Oscilloscope (2 channels minimum) and probes
• Digital multimeter (frequency counter is a plus)
Service fixture tests
1. Start-up sequence—Turn on the service fixture's power
switch and watch the amplifier's LED display on the front
panel. The clip/protect indicator LEDs should light briefly and
then go out. (If they stay on, then it is usually because an audio
signal is being put into the amplifier inputs. Disconnect any
input signals for this stage of testing.)
The amplifier should start with its normal sequence. You
should hear a small relay click after about two seconds,
followed by a large relay click about two seconds after that.
2. Regulated +5 volts—Check for the regulated 5 volts DC at
the "+5V REG." terminal (reference to the fixture's ground
Do not connect amplifier
to AC mains yet.
Test Point B
To AC mains
100–240 VAC
50–60 Hz
TEST POINT B
Remove two jumpers
from Test Point B.
Connect long lead to
Test Point A and short
lead to Test Point B.
11