"Arfa Daily" wrote in message
...

wrote in message
ups.com...
Something on the DSP board is locking up the I2C data bus lines.
Pretty common problem during storm season on similar Pioneer models a
several years ago.
Had my own DSP ic fail in this way. $35 flat pack ic fixed it.

David

David Farber wrote:
This Pioneer VSX-D908S analog/digital receiver will not pass any audio
as
long as the dsp board is plugged into the unit.

First I'll explain what works with this set. With the dsp board
removed,
all analog input functions work as long as you select the direct mode.
The
direct mode bypasses the digital board completely. For example, if
you've
selected CD direct (analog) for the source, there is an electronic mode
switch, located on the main control board, which selects between dsp,
direct, or 5.1. This switch will select the direct mode correctly and
pass
the audio signal. What doesn't work is if you plug in the dsp board,
the
audio does not pass through the same analog/digital mode selector on
the
main control board even in direct (analog) mode. The dsp board is quite
complex but there is a uP there that communicates with the control
board's
uP. Now here's where I have, hopefully, an easy question. Two of the
pins
on
the uP of the dsp board are labeled Xin and Xout and they have no
signal.
On
the uP of the control board, there is good signal at the uP on the Xin
and
Xout terminals. Can I generalize that any uP that has two terminals
labeled
Xin and Xout should have a continuous running clock signal on these two
terminals? Also, would the uP itself be the most likely failure to
cause
this symptom? By the way, I spent a fair amount of time removing all
the
boards and soldering numerous bad connections.

Thanks for your reply.
--

Xin and Xout are usually the terminals that connect the internal clock
generator to the external clock crystal, and you would normally expect to
see a continuous clock signal on at least one of them, but note that you
need to be using a x10 ( low capacitance ) probe on your scope to have any
hope of seeing a signal ( mostly ). On some clock generators, notably one
that runs a DSP chip in a Sony HC system, as soon as you come near the
xtal
with even a low capacitance probe, the oscillator stops, never to restart
until you depower then repower to produce a reset to the DSP chip, so the
upshot of all this is that your DSP oscillator may possibly be running,
and
nothing to do with the fault, and stops when you try to scope it. A better
indication may be if there is any activity on any of the other pins.
However
this also does not give any certain proof of clock activity, as you may be
seeing shared-bus activity, originating elsewhere.

You may yet have xtal trouble though, particularly if it is a surface
mount
genuine crystal, rather than a ceramic resonator, which tend to be more
robust and reliable. I have had a number of these xtals fail in a variety
of
products. Sometimes, they are just reluctant to start up, and just
removing
the xtal, and soldering it back in the other way about, is enough to get
them going. If the problem genuinely is clock related, then it is far more
likely to be the xtal, than the chip.
If it has been subject to storm activity though, then the chip becomes
more
likely, as suggested by the other poster.

Arfa




I do use a x10 low capacity probe. I have tried to touch up the soldering
around the xtal (it's a ceramic resonator type if I'm not mistaken) but it
made no difference. I'm going to try the uP replacement and I'll report
back, successful or not.

Thanks for your reply.

--
David Farber
David Farber's Service Center
L.A., CA