Alesis Microverb IV User manual

10-22-02
Microverb (C4) General Description
The Alesis
MicroVerb IV is the
latest in the line of
popular effects
processors of the micro
series. Similar in
performance to the
MicroVerb, the
NanoVerb is a scaled
down version.
Combining the well
known power of Alesis
custom processing with
small size and
affordability, the
MicroVerb IV (Product
Code C4) and NanoVerb
(Product Code NV) are
based largely on the
design of the MidiVerb
IV. The MidiVerb IV
custom chip set, along
with the latest ADC and DAC technology help make the C4 and NV two of the most
powerful signal processors in their price ranges. Particularly in the NV the use of surface
mount technology helps push the envelope of size and weight verses performance.
Reference designators for the C4 are taken from the Rev. C schematic. Reference
designators for the NV are taken from the Rev. B schematic and are denoted by brackets
{} when components are functionally similar to the C4. Note that for both of these units
there are several different main PCB revisions. There are no functional differences
between these revisions. However, it should be noted that older PCB revisions will have
some wire jumpers that later rev.s incorporated into the PCBs. Figure 1 shows the
simplified block diagram of the C4. As the NanoVerb is even simpler, there is no need to
simplify it beyond the schematic.
Figure 1
C4 Service Manual V1.01

10-22-02
Test Procedures
C4 Self Test
The MicroVerb 4 has two self test modes which allow the user to run diagnostic
tests. In Individual Test mode, the user can select particular tests to run. In All Test
mode, the MicroVerb 4 runs all of the tests in series.
- Power up the unit while holding down the Bank button.
To enter Individual Test mode:
à- Use the Value Dial to select which test to run (each test is described below).à
à- Press Store to execute the test. When the test is complete, you can either select
another test to run or exit Individual Test mode by holding Bank and pressing Store.
à- Power up the unit while holding down the Store button.
To enter All Test mode:
C4 Individual Test Descriptions
4 t0: ROM Test. If the unit passes, the MicroVerb 4 will display "P0" and exit the test
automatically. If the unit fails, the MicroVerb 4 will display "F0" and won't exit the
test. In this case, the user must press Bank to exit.
4 t1: EEPROM Test. If the unit passes, the MicroVerb 4 will display "P1" and exit
the test automatically. If the unit fails, the MicroVerb 4 will display "F1" and won't
exit the test. In this case, the user must press Bank to exit.
4 t2: LED Test. Lights up all the LEDs (first, column by column; then row by row).
The C4 automatically exits this test.
4 t3: Switch/Encoder Test. Checks the buttons and the rotary encoder. The user must
press every button AND rotate the encoder in both directions in order for the test to
pass. After doing this, the user should hold Bank and press Store. If at this point all
of the buttons have been pressed (i.e., the unit passed), then the MicroVerb 4 will
display "P3" and exit the test. If instead not all of the buttons have been pressed, the
MicroVerb 4 will display "F3". The user can either restart the test (by pressing Store)
or exit the test (by pressing Bank.)
4 t4: Edit Knob Test. Checks the Edit A/B knobs. The user must rotate each knob to
show all values (0 to 127) in order for the test to pass. To exit the test, press Bank.
4 t5: MIDI In/Out Test. Before running this test the user must connect a MIDI cable
from the MIDI Out to the MIDI In of the unit. If the unit passes, the MicroVerb 4 will
display "P5" and exit the test. If the unit fails, the MicroVerb 4 will display "F5" and
won't exit the test. In this case, the user must press Bank to exit.
4 t6: DSP RAM Test. If the unit passes, the MicroVerb 4 will display "P6" and exit
the test automatically. If the unit fails, the MicroVerb 4 will display "F6" and won't
exit the test. In this case, the user must press Bank to exit.
Additional Test Procedures
Audio Test. Plug an audio source into the Left Input. Don't plug anything into the
Right Input. Verify that audio is passed through (the Input meters should light). Next, test
the Right Input (with nothing in the Left Input). Finally, plug a different audio source into
each of the Inputs. Verify that the Left Output passes audio from the Left Input and verify
that the Right Output passes audio from the Right Input. In addition, all knobs should be
turned through the entire range to ensure 1. Audio potentiometers are smooth and there
are no audio dropouts or “scratching” noises heard, and 2. Edit knobs/data wheels
correctly switch/change the corresponding parameters in accordance with the unit’s User
Reference Manual.
C4 Service Manual V1.01

10-22-02
Troubleshooting Chart
The charts below were created in an effort to relieve the beleaguered technician
from having to "discover" some of the common faults we have seen. Please note that we
only cover the most likely causes, not all of them.
C4 Symptom Possible Cause Solution
No Lights, No Sound. (Dead). Faulty AC adapter. Replace and retest.
Defective component in power supply circuit. Troubleshoot and repair as necessary.
Loose front panel cable. Troubleshoot and repair as necessary.
No wet (effects) signal. Faulty ASIC Replace and retest.
Faulty DRAM Replace and retest.
Faulty Crystal Replace and retest.
Faulty DAC Troubleshoot and repair as necessary.
Faulty ADC Troubleshoot and repair as necessary.
Distortion. Faulty Power Supply Rail Troubleshoot and repair as necessary.
Faulty op-amp Troubleshoot and repair as necessary.
Faulty DAC Troubleshoot and repair as necessary.
Faulty ADC Troubleshoot and repair as necessary.
Programs not changing. Faulty shaft encoder. Replace and retest.
Intermittent operation. Faulty Crystal. Replace and retest.
Faulty potentiometer(s) Replace and retest.
Poor through hole Solder Check all through hole solder connections,
particularly near the power supply area.
C4 Service Manual V1.01

10-22-02
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.
C4 Service Manual V1.01