ALESIS HR-16 - Manual (Page 21)

HR-16/HR16B Service Manual 1.00 15
8.0 Common Solutions
A thorough knowledge of the software history can help solve a great many situations quickly.
Also be aware that with devices as full of options as the HR-16(B), there are even more possibilities
for user error (i.e. the user claims that MIDI out isn't working, but on checking the settings, the tech
finds that both MIDI clock, and DRUM NOTES OUT are turned off). Understanding how the user
has the unit in his (her) setup is an important tool in troubleshooting units that act like there is
nothing wrong with them.
While it is simply beyond the scope of this manual to present every possibility, the chart
below offers a majority of solutions to common situations.
Complaint Possible Cause Solutions
Unit is truly "dead". (No lights, or sound) Blown power supply. Replace and retest.
+5V rectifier blown (D5). (Note that 1N4001s
were used originally, but some were found to
be unreliable. We have since switched to
using 1N4004s exclusively.) Troubleshoot and repair as necessary.
Blown DM3AG ASIC. (occasionally these
devices will "short" and pull down the 5V
supply rail) Remove ASIC and attempt power up. Also
note that this type of ASIC failure usually
causes the ASIC to become extremely hot to
the touch.
Blown +5V filter capacitor (C5)
Usually blown capacitors will display a
"distended" appearance. Troubleshoot and repair as necessary.
Faulty or broken power jack. Troubleshoot and repair as necessary.
Faulty or broken power switch. Troubleshoot and repair as necessary.
Broken lead on power choke. Troubleshoot and repair as necessary. (see
section 7.16)
Blown monolithic filter capacitor. (Any of the
small blue RAM capacitors used as bypass
capacitors can become shorted and pull the
rail low. We are currently using ceramic disk
capacitors as replacements exclusively) Troubleshoot and repair as necessary. Note
that when these capacitors fail, they often turn
brown from overheating, and some will
occasionally just burn up.
Unit powers up, but does not function. (No
LCD display, all LEDs on, buttons don't work,
etc.) Unit is simply "crashed". Reinitialize memory and test.
C-20 leaking excessively. Troubleshoot and repair as necessary. (see
section 7.13)
Faulty 8031, EPROM, or SRAM. Troubleshoot and repair as necessary. (see
section 3.X)
Faulty DM3AG ASIC. (Pulling down the 8031
data buss.) Troubleshoot and repair as necessary.
Faulty I/O latch pulling down lines on data
buss. Troubleshoot and repair as necessary. (see
section 3.2)
Other faulty reset component. Troubleshoot and repair as necessary. (see
section 3.1)
Open or short in 8031 data buss. Troubleshoot and repair as necessary. (see
section 3.X)
Open or short in 8031 address buss. Troubleshoot and repair as necessary. (see
section 3.X)
Faulty LCD pulling down lines on data buss. Test with new LCD.
LCD shows no, or scrambled display (the rest
of the unit seems to function normally). Faulty LCD. Test with new LCD.
Faulty LCD cable. Replace and retest.
Faulty 74HC138 (U13), or open between U13
and LCD header. Troubleshoot and repair as necessary.
Intermittent reset. C-20 leaking excessively. Troubleshoot and repair as necessary. (see
section 7.13)
Faulty 8031, EPROM, or SRAM. Troubleshoot and repair as necessary. (see
section 3.X)
D15 is glass package type (Revision A or CA
only). Replace with metal package type (see section
7.2).
R116 is pulling 8031 Vcc too low (revision AQ
only). Add jumper across resistor.
Complaint Possible Cause Solutions