Deaf Alesis HD24
wrote ...
The first thing I would do is to check the analogue power supplies,
which should be something around +15v and -15v. (possibly as high as
+- 18v) If one or both voltages are not present in the analogue
section, the machine may well behave as though there is no analogue
circuitry present, while the computing section, running on 5volts,
will be unaffected and even unaware the analogue section is not
working.
If the analogue section uses 8 pin DIL op-amps, this is the easiest
place to check - select a convenient chip and carefully meter each of
the 8 pins in turn, with the negative meter probe on a ground point.
Make sure you don't short 2 pins together with the probe, or you could
kill the chip.
Thanks, Gareth. Alas, the analog I and O boards are all small-pitch
SMD components, so the trusty method of checking VCC and VDD
for +/-15V isn't quite as convenient. Now that I have it back home,
I'll do some better troubleshooting ("fault-finding" has a different
meaning over on this side of the Pond! :-) I'm going to try to see if
I can discover what the nominal voltages on the power harness are
supposed to be.
The HD24 worked great on the 230V 50Hz in Romania, but now that
it is back home here in 120V-land, maybe it has become wimpy? :-)
(The switched-mode PS runs on 100-240v, no user control, so I
didn't forget to set the power back.) The digital parts of the unit
work perfectly, which would appear to indicate that the +5 is good.
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