Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <nospam-0512042136260001@192.168.1.177>,
Paul <nospam@needed.com> wrote:
>In article <cp00kn$gbl$1@panix5.panix.com>, adykes@panix.com (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/downloads1-3.aspx?refdesign=True&compamodel=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
Thanks for the thoughtful response. I hadn't though
of chassis grounds.
--
a d y k e s @ p a n i x . c o m
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