Other Probable Causes Of Noise; One Or More Red Lights On The Front Panel Are Blinking; Problems With The Whole A/V System - Sherbourn PA7-150 User Manual

NOTE: Never remove the ground pin from any
power cords (if present). This is very dangerous.
If the hum persists, disconnect all the source components
one at a time from the back of the preamplifier, until you
identify the problem.
• Try moving the speaker cables away from any power
cords. Try just one speaker, connecting it to each
amplifier channel and see if one channel is bad.
• Check that the interconnect cables to the amplifier do
not have any broken connections. The best way to do
this is to substitute a known good connection for the
suspect connection. If you reverse the cables and the
problem goes away, the cable may be damaged or
broken. This is possible even if you can't physically
see the break as the strain for pulling on audio cables
can sometimes break the wire internally.
Ground loop isolators are available for audio lines and
video devices. If you need assistance, contact Sherbourn.
Although this is not always an ideal solution, the ground-
ing differences between certain home entertainment com-
ponents sometimes require ground loop isolators. This is
the exception rather than the rule.

Other Probable Causes of Noise

• Speaker noise may also be caused by interference or
noise on your AC line. Make sure there are no large
appliances sharing the line, or halogen lamps or light-
dimming Triac devices.
• Try connecting your system to another AC socket on
a separate line.
• If the hum is heard from within the 7-150, and not
through the speakers, this may also be caused by in-
terference on the AC or DC lines. The power trans-
formers may turn this interference into an audible
noise. Internal hum can be made worse by a shelf or
cabinet resonating, so try moving the 7-150 to anoth-
er shelf.
• Try moving your components further away from the
TV, especially if you notice the screen has changed
color in the area closest to the component.
• If you have very high efficiency speakers, these may
tend to reveal noises, which other speakers do not.
One or more RED lights on the Front Panel are
Blinking
Your 7-150 Amplifier is equipped with a 'Protect Mode' to
minimize the possibility of damage to either itself or
speakers. If a problem is detected, the channel(s) at risk
will shut down, following a red blinking on the corres-
ponding indicator light(s).
Each RED light indicates a fault condition for the corres-
ponding power module.
A fault condition is one or more of the following:
• Excessive Operating Temperature
• Excessive Current (Short Circuit)
• DC on the Outputs
An excessive temperature fault can be reset by allowing
amplifier to cool and cycling power on/off button on the
front panel. Excessive current (short circuit) can be reset
by removing the cause of the short and cycling power
on/off button on the front panel. DC at output is a possible
fault condition that is equipment related and requires tech-
nical assistance. Please contact Sherbourn if you have re-
peated problems causing the RED front panel light to flash
that are NOT thermal or short circuit related.

Problems with the whole A/V System

If you are having more complex problems in your overall
home entertainment system (not just with the amplifier),
please contact Sherbourn Support for assistance.
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