Chapter 6: Troubleshooting; Hum; No Volume; Distorted Or Low Level Sound - Alesis RA-100 Reference Manual

CHAPTER 6:
TROUBLESHOOTING
Begin the troubleshooting process by re-reading the manual to make sure you
didn't miss some important point regarding the unit's operation. After that,
try the following techniques for specific problems.

Hum

Turn down the volume controls. If the hum goes away, then the source of the
hum is either in a unit feeding the RA-100, or in the input cables feeding the
RA-100. Check your cables and other units.
If the hum persists, there may be a ground loop. Follow the advice given in
section 3.4. Also, check to see that the RA-100 is not situated near other
devices with large external hum fields.
If a loud hum continues, there may be a problem within the RA-100.

No Volume

Turn up the volume controls with no signal feeding the RA-100, and listen
very carefully to the speakers. If you hear any hum or noise, no matter how
low level, then the RA-100 is receiving power and the problem probably lies
in the equipment or cables feeding the RA-100.
If the speakers are absolutely dead and make no noise whatsoever, check the
speaker cabling.

Distorted or Low Level Sound

If either of these problems occurs after the RA-100 has been on for a long time
and running under a heavy load, it is possible that the output protection
circuitry has kicked in. Let the unit rest for a minute by turning off the power
and see if the problem goes away. If it does, check for thermal problems such
as obstructed air flow around the unit.
Bad cables can also cause distorted or low level sound—yet another argument
for using the best cables you can afford.

Thin Sound/Sound that Changes Unpredictably in a Room

This is generally the result of mismatched speaker polarity. Refer to section
3.2 for information on how to test for proper polarity.
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