Alesis QS Series Keyboards Service Manual V1.00 v 11/19/06
General Troubleshooting
While this manual assumes that the reader has a fundamental understanding of
electronics and basic troubleshooting techniques, a review of some of the techniques used by
our staff 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.
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