TROUBLE SHOOTING HINTS
Check the speaker fuses first when there is little or no sound.
A blown fuse will pass a low level distorted signal. If the pilot
lamp is steady. excessive DC at the output may be holding the
relay open. If the lamp blinks, then the thermal protective
circuitry has shut down the amplifier.
Always check external factors such as cables and signal
sources before dismantling the P505. Once the cover is
removed. do not attempt to move the amplifier by the front
panel handles! Check the internal fuses. The line fuse is near the
power switch. The two dual fuse holders monitor the B + and
B - ‘rail‘ voltage. Failure of any of these indicates a circuit
problem. unless the amplifier was undergoing very high power
tests into a low impedance load. where the fuse sizes may need
to be increased.
If the amplifier requires factory service, and the power
transformer output appears normal when its secondary leads are
disconnected from the diode bridge, the transformer can be
removed, and the rest of the amplifier returned for service. This
greatly reduces the cost of shipping, and the risk of damage in
transit. If you have isolated the fault to the audio module. you
may prefer to disconnect it. and return it as a unit (fan. heat
sinks, circuit boards). Four screws secure it to the chassis. Be
sure you tag every wire as you unsolder it. When packing it,
wrap it first to prevent particles of packing material from
becoming trapped, and provide plenty of cushioning.
d & O -
-
~
-
m
40
0.8
PC-19 COMPONENTS
SQUARE WAVE RESPONSE WITH A REACTIVE LOAD
120 volts peak to peak into ohm resistor in parallel with mfd.
loo Hz
8
