In article <cp00kn$gbl$(E-Mail Removed)>,
(E-Mail Removed) (Al Dykes) wrote:
> Is the fix to just pop in a real sound card ? I assume I can disable
> the mobo sound in the CMOS, somehow.
>
> One channel of the mobo sound output jack on my A7N8X Deluxe has gone
> out. The volume control applet shows that all the balance controls
> are centered. A reboot doesn't fix anything.
>
> When I slide the balance control to one extreme I hear _nothing_. In
> the other direction I get full level audio in one ear.
>
> I've tried a couple pair of headsets and the effect is the same. I
> wiggled the jack and don't get any intermittant connection. I have
> this output jacked into the HiFi system fill time, so it doesn't get
> many insertion cycles. Even if it was the jack I don't think
> it can be fixed.
>
> Any suggestions ?
All the outputs are capacitively coupled. About all you can do
from a diagnostic point of view, is monitor the output right at
the chip pins itself, for debugging purposes. In the reference
schematic, I don't think there is anything hanging off the Lineout
left and right signals (no sharing circuit):
http://www.realtek.com.tw/downloads/...pamodel=ALC650
Best site for download - 2MB
ftp://202.65.194.18/pc/ac97/alc650/alc650_data5.zip
Unzip file, then unzip ALC650_DEMO_CIRCUIT_VER_11.zip, to
find alc650_demo_circuit_ver_11.pdf
So, things to check.
1) Something grounding to the bottom of the board ? Some of the
A7N8X family boards use 9 standoffs, and your cases may have had
10 standoffs screwed into them. The extra standoff can short to
some of the audio circuit.
2) Check the FPAUDIO header. Jumpers sometimes corrode. Remove the
two jumper plugs and reinstall them in their original location.
That little bit of scraping, may improve the contact of the
shorting jumpers.
3) If using front panel headphone jack, remove wiring assembly from
FPAUDIO, and put the two jumpers back. See if Lineout returns, in
which case, the problem is with the front panel wiring.
4) When all else fails, examine the demo_circuit above. Line-L and
Line-R are pins 23 and 24. With no audio output signal applied,
the DC level on the pins should sit at mid-rail (i.e. the output
is driven by a DAC, and code point 0x0 should be a voltage between
VDD and VSS, perhaps 2.5V. To work, the quiet voltage cannot get
too close to the rails, or the signal will be clipped). Compare
the reading on pin 23 and 24 for similarity, as much as anything.
You can also flip the meter to AC volts, and take a measurement
for both channels. Next, take a recording of a stereo 1KHz test
tone, and play in on Lineout at full volume. Probe with meter
again, and see if the AC reading on both channels is the same.
The output is supposed to be 1Vrms or so, and a typical cheap
multimeter when set on AC, will read the combined total of the
AC and DC components (and I'm not even going to guess what the
reading will be). If, again, both channels read the same, higher
value, then you know the chip isn't blown.
Note: The pins are extremely tiny, and chips with these tiny
pins cannot take a lot of probing. I use needle points on my
multimeter, for circuits like this. If you probe too much, you
run the risk of scraping solder off one pin and onto a neighbour,
or bending the IC pins. You really need to work with the board
outside the case, and use a good magnifier on a stand, to be
able to probe safely. I don't really consider this step of
debugging to be that practical (I probably would be throwing
in the towel at this point, rather than wasting time pulling
the board etc.)
5) In demo_circuit, page 4, upper left hand corner, the ref
design shows the inclusion of room for serial resistors. So,
that makes the audio path: chip, series 1uf capacitor, series
resistor (could be a zero ohm shunt), FPAUDIO header jumper
plugs or front panel audio wiring, then back through the
circuit board, to the Lineout jack on the back.
There is an "onboard AC97 audio controller" in the BIOS, and you
can disable that if you want. Check Google to see if anyone has
had problems with installing a third party sound card on the
board. I don't remember any posted problems with that.
HTH,
Paul
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