Power Amp Test - Warwick WA600 Service Manual

3. Power amp test

Necessary tools: sine wave generator, oscilloscope
1. Disconnect backboard and preamp
board
2. Connect speaker output to the power
amp board
3. Connect external signal generator
(suggested setting: sine wave 1kHz/0V)
to the input of power amp (pin marked on
yellow is input, pin marked on red is
GND). CAUTION! You need to connect to
each other both GND pins marked on red.
Without this connection power amp
safety circuit will not turn on the relay
switch.
4. Connect 4ohm load (at least 600W) to
speaker output on the back of the amp
5. Connect oscilloscope probe to signal
output. Make sure that oscilloscope
ground is connected with generator
ground (GND) or red GND point.
6. Connect power cable, turn on the power
switch and start to increase generator
voltage. You should see increasing clean
sine wave on the scope. While input
voltage reaches 4Vpp, output voltage
should reach 140Vpp. At this point
increasing signal input will not increase
signal output (built in limiter starts to
work)
7. If you don't see sine wave on the scope or
you see the sine which is highly distorted
or clipped at much lower voltage, then
power amp with power supply need to be
exchanged.