Alesis MIDIVERB IV, Service Manual

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Alesis MidiVerb IV Service Manual‘ v 03/05/99
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.
1. 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).
2. 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.
3. 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).
4. 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.
5. Cable Checks - Wiggling cables can reveal intermittent failures such as loose cables or poorly soldered
headers. Remember to check power supply cables as well.
6. Flexing the PC Board - Poor solder joints and broken traces can often be found by pressing the PC
Board in various places.
7. Tapping Components - Sometimes tapping on a component (particularly crystals) will cause it to fail.
8. Power Down/up - Turning the unit off and back on rapidly several times may reveal odd reset and/or
power supply failures.
9. 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.
10. Compressors - Using a compressor/limiter is often helpful when attempting to solve low level noise
problems, as well as assisting with DAC adjustments.
11. Sweep Tests - Sweep generators are very useful in checking the frequency response envelopes of anti-
aliasing filters.
12. Piggybacking - Piggybacking I.C.s is particularly useful when troubleshooting large sections of logic.
This is especially true when working with older units.