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Tips
& Tricks
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My
Main Outs died, any advice? August
2, 2002 ~ BHQ recently posted the following
problem: <
Hello all. My main outs didn't survive the trip to
Amsterdam and back. The signal is intermittent and
very quiet and I'm assuming they are for all
practical purposes dead. Have any of you had the
problem of outputs dying and if so, how
easy/difficult was it to repair or get repaired? I
figured I would ask my X peers before I flip out
and drop a ton of cash getting it professionally
repaired. ;) btw, I've temporarily circumvented the
problem by running an insert cable out of the
headphone jack. > To
which Shifty replied (at length): "Before
you read this, you should know that in my travels
scanning through the operating system of this
machine, I have discovered diagnostic messages. I
couldn't figure out how to actually run the
diagnostic tests for it, but it would useful to
know, perhaps Ensoniq Tech Support can
help!" General
Output Signal Diagnostic Guide -------------------------------------------- Hmmm.
you might want to figure out where the problem is.
The signal path goes: dsp->codec->mini-amplifier->output
jacks/headphones. So
my first question is, how do the headphone outputs
work? Do
they sound crappy, *exactly* like the main outs? If
so, then the problem is "upstream" from the
mini-amp/codec etc. If they sound okay, then it's
probably just the soldering between the mini-amp
and the headphones. If
you need to trace the signal further up the
chain: If
you have some probes, or can improvise (small paper
clip?) you can pop the top off, make and run a
sequence that continuously generates sound through
the main outputs. Listen to that through an amp.
Then, connect your homemade probe to another,
separate amplifier. Probe the signals that go from
the codec out to the mini-amplifier. The codec is a
burr-brown PCM1718 (Note: Burr-Brown was recently
bought by TI, everything is on TI's website, you
can still search on "PCM1718") and is located
near-ish the main output jacks. It's a very small
IC, 20-pin ssop. You can see Burr-Brown's logo on
the chip, it looks like this: http://www.burr-brown.com/elements/bb1.gif Take
a look at the picture on page 3 of the PCM1718
spec: http://www-s.ti.com/sc/psheets/sbas050/sbas050.pdf You
want to find the output pins, they're numbers 9 and
12. Pin 10 is the analog ground. So, connect pin 10
to the "ring" of an amplifier and 9 to the "tip" to
test the right output. And instead of 9, pin 12 to
the tip to test the right output. What you want to
hear is the same as the expected output, only much
quieter. If it sounds good, then the problem is
downstream - bad amp, bad jacks, etc. This is a
Good Thing. Because you can take it to any good
electronics shop and they can fix the output
amplifier for you. If
it still sounds like @#&* coming out of the
codec, then you need to get yourself an
oscilloscope. Use it to examine the *digit inputs*
to the codec. Those are pins 4, 5, and 6. Take a
look at those signals. They should appear like
digital highs and lows, 5V peak to peak. The bit
rate should be somewhere a bit higher than 44.1 kHz
* 32. Again, looking at page 3 of the PCM1718 spec,
you can see the pin descriptions. Pin
4 should be a clock @ roughly 44 kHz * 32 Hz. Anyway,
what you want to find out here is If
that still doesn't help, you gotta go even DEEPER!
You should examine all of the other pins on the IC
to make sure they're cop acetic. That page 3 of the
spec should help you. You
could resolder/reflow the flaky pins on this chip.
Perhaps you could replace the 10uF capacitors on
pins 8 and pins 13. If
the problem is upstream from this chip, though, you
are in trouble, because that means it's from an
Ensoniq custom IC! The only options you have are to
combine parts from broken ASR-X's. if
ALL ELSE fails, here's what you do: go on eBay, put
it up for sale and say that you have the ULTIMATE
GLITCH ROCK INSTRUMENT! :) :) BTW,
I wrote this to be a very general diagnostic guide
for people, since your headphones work, you are
very lucky...it's probably just a weak solder joint
problem (1/4" jacks should NEVER be soldered to a
board, they should ALWAYS be panel-mounted, because
solder can't handle the stress). Take it to a
decent shop, and they'll resolder for you. It
should take less than 1 hour, and should cost less
than $50 - a minor annoyance compared to the bugs
in the O.S. :) -N |
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