Alesis DEQ230, Service Manual, Page: 5 / 38

Confidential Alesis Service Manual 8-31-0103-A
General Troubleshooting
While this manual assumes that the reader has a fundamental understanding of electronics
and basic troubleshooting techniques, a review of some of techniques may help.
° Visual Inspection - A short visual inspection of the unit under test will often
yield results without the need of complex signal analysis (burnt, or loose
components are a dead giveaway).
° Self Test - Alesis products that utilize microprocessor control contain built in test
software which exercises many of the units' primary circuit functions. Self test
should always be done following any repair to ensure basic functionality.
° Environmental Testing - Applying heat and cold (heat gun/freeze spray) will
often reveal thermally intermittent components (Clock crystals, I.C.s, and
capacitors are particularly prone to this type of failure).
° Burn in Testing - Leaving a unit running overnight often reveals intermittent
failures such as capacitors that begin to leak excess current after a significant
amount of time.
° Cable Checks - Wiggling cables can reveal intermittent failures such as loose
cables or poorly soldered headers. Remember to check power supply cables as
well.
° Flexing the PC Board - Poor solder joints and broken traces can often be found
by pressing the PC Board in various places.
° Tapping Components - Sometimes tapping on a component (particularly
crystals) will cause it to fail.
° Power Down/up - Turning the unit off and back on rapidly several times may
reveal odd reset and/or power supply failures.
° Reset Threshold - A Variac (variable transformer) can be used to check reset
threshold levels. This can be particularly useful in helping customers with low
line problems.
° Compressors - Using a compressor/limiter is often helpful when attempting to
solve low level noise problems, as well as assisting with DAC adjustments.
° Sweep Tests - Sweep generators are very useful in checking the frequency
response envelopes of anti-aliasing filters.
° Piggybacking - Piggybacking I.C.s is particularly useful when troubleshooting
large sections of logic. This is especially true when working with older units.
° Assembly/Disassembly Organization - When removing assemblies, organize
screws and clips with the assemblies that they were removed from. Organizer
trays save a lot of time during re-assembly since similar screws and clips will not
be mixed with each other.