Front panel audio problem - asusp4p800 + hp compaq tower

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wolf7878

Hi all,
My problem is:
I changed my chassis to a hp compaq dc7600 tower and now the front
panel audio is not working correctly: only the headphones working the
mic is not. If anyone can help how to change the wiring to work the
mic, I tried several way. I attached an image, on the left side with
the case wiring (more precisely it is the connector of the old
motherboard from the case), and on the right side is the asus mobo
connectors.
Thanks in advance.
Regards, Wolf

http://img152.imageshack.us/img152/6726/frontaudioqa4.jpg
 
wolf7878 said:
Hi all,
My problem is:
I changed my chassis to a hp compaq dc7600 tower and now the front
panel audio is not working correctly: only the headphones working the
mic is not. If anyone can help how to change the wiring to work the
mic, I tried several way. I attached an image, on the left side with
the case wiring (more precisely it is the connector of the old
motherboard from the case), and on the right side is the asus mobo
connectors.
Thanks in advance.
Regards, Wolf

http://img152.imageshack.us/img152/6726/frontaudioqa4.jpg
Click to expand...

I would use a multimeter and verify the names on the HP
side. In particular, I don't like the mention of "sleeve"
on pin 3.

The three contacts on a 1/8" stereo miniplug are:

Tip, Ring, Sleeve.

With an AC'97 microphone, connector signals are

Mic-In, Mic-PWR, Ground

The headphone jack would be

Left-Out, Right-Out, Ground

The signals on the Asus pin 1 and pin 3 are
MIC2 and MICPWR, and they should go to Tip and Ring
respectively. For some reason, the HP has "sleeve",
which would be the ground on the connector. So I'd
want to check and see if they really did that or
that is a typo.

Paul
 
Thank you for your answer, now I try to get a multimeter and will
check the contacts.
Then I write back with the result.
Regards, Wolf

Paul írta:
 
Hi Paul,

So here are the wires from the hp side (I checked with a multimeter):

1 - black (thin) -> mic tip
2 - black (thick) -> mic and headphone sleeve
3 - white -> mic ring
4 - nc
5 - red -> headphone ring
6 - green
7 - black (thick) -> mic and headphone sleeve
8 - nc
9 - yellow -> headphone tip
10 - blue (btw. it is marked as nc!)

The two black (thick) wires (2 and 7) are grounded together.

Any idea?

Thank you in advance.

Regards, Wolf

Paul írta:
 
Hi Paul,

So here are the wires from the hp side (I checked with a multimeter):

1 - black (thin) -> mic tip
2 - black (thick) -> mic and headphone sleeve
3 - white -> mic ring
4 - nc
5 - red -> headphone ring
6 - green
7 - black (thick) -> mic and headphone sleeve
8 - nc
9 - yellow -> headphone tip
10 - blue (btw. it is marked as nc!)

The two black (thick) wires (2 and 7) are grounded together.

Any idea?

Thank you in advance.

Regards, Wolf

Paul írta:
Click to expand...

FP_AUDIO header on the P4P800 (copied from your picture).

1 2
MIC2 x x AGND
MICPWR x x +5VA
Line_out_R x x BLINE_OUT_R
NC x
Line_out_L x x BLINE_OUT_L
9 10

Your HP wiring looks like this -

Tip, Ring, Sleeve
Microphone MIC2, MICPWR, AGND
Headphone Line_out_L, Line_out_R, AGND

black thin MIC2 x x AGND black thick (MIC sleeve)
white MICPWR x x (NC)
red Line_out_R x x green
black thick AGND x nc?
yellow Line_out_L x x blue NC?

MIC TIP x x MIC SLEEVE, HEADPHONE SLEEVE
MIC RING x x (NC)
HEADPHONE RING x x
x
HEADPHONE TIP x x

Your original complaint was that the microphone was
not working. Yet, the microphone tip, ring, and sleeve
seem to be connected to the correct pins. In fact,
the wiring is consistent with an AC'97 header (the AGND
on pin 7 isn't, but shouldn't matter).

The blue and green, are supposed to be returning analog
signals from the headphone jack. They are intended to
support a "muting" function on Lineout on the back of the
computer. In theory, when a headphone plugs in, red (5) to
green (6) would be open circuit, yellow (9) to blue (10)
would be open circuit. When the headphones are not
plugged in, switch contacts are supposed to connect red to
green, and yellow to blue. The switch contacts make the
Lineout work, when no headphones are present. And when
headphones are installed, then no signal is sent to Lineout.
That is what gives the muting function for AC'97. Cheaper
cases don't have the switch feature, and may leave (5) to (6)
shorted, and (9) to (10) shorted on the case side.

I would check carefully again, what relationship there is
between pins 1, 2, and 3 of your HP wiring. Using the ohmmeter
on a high range, there should be no connection between pin 1,
2, and 3. If you were using an electret microphone, it would
take power from pin 2. If pin 2 is being loaded, and pulled
down, that would stop the electret from working. So I'd be curious
as to what is up, between pins 1, 2, and 3.

Did the wiring ever work ? Was there ever a working
microphone with the original HP setup ?

Paul
 
Paul said:
If you were using an electret microphone, it would
take power from pin 2. If pin 2 is being loaded, and pulled
down, that would stop the electret from working.
Click to expand...

That should have been pin 3. The electret takes power from pin 3,
which is MICPWR. MICPWR should be somewhere between 3 to 5 volts
or so, with a 2K ohm series resistor. Electret microphones vary,
as to how much voltage they need at a minimum.

To test that your microphone works with your P4P800, test the
microphone using the jack on the back of the computer first.
If your microphone is an electret, the same MICPWR should be
available to you on the rear microphone connection.

In the sound control panel, sometimes there is a hidden
setting, to switch between MIC1 and MIC2. Make sure that you
have selected the right microphone, when doing your testing.

Note the "Advanced" button below the Microphone setting. When
you click that, there should be a selector for MIC1 or MIC2.
I couldn't find a picture of the Advanced dialog...

http://forms.analog.com/Form_Pages/soundMax/images/mixer3.GIF

Paul
 
Hi Paul,

Thank you for your kind assistance again.
The same headphone-mic pair perfectly working with the rear panel
connectors (so I think on the mobo side everything is ok). Beside this
when I plug the mic and headphone to the rear or even to the front
connectors, the soundmax program automatically detect the devices and
offer the configuration of them. If I use the rear panel and I choose
this configuration step both device work perfectly. If I use the front
panel and I choose this configuration step only the headphone working,
at the testing of the mic it says no siglnal on the mic.

Regards, Wolf
 
Hi Paul,

Thank you for your kind assistance again.
The same headphone-mic pair perfectly working with the rear panel
connectors (so I think on the mobo side everything is ok). Beside this
when I plug the mic and headphone to the rear or even to the front
connectors, the soundmax program automatically detect the devices and
offer the configuration of them. If I use the rear panel and I choose
this configuration step both device work perfectly. If I use the front
panel and I choose this configuration step only the headphone working,
at the testing of the mic it says no siglnal on the mic.

Regards, Wolf
Click to expand...

Ok, your next test is a simple one.

Pull the HP wiring harness from the FP_audio header.

Using your finger, touch the MIC2 (pin 1) pin. If the microphone
circuit is working, you should pick you some "hum" in your computer
speakers. (Turn the volume down on the speakers first, then bring it
up gradually, so you don't blow out an eardrum.)

The purpose of doing this, is to see if the MIC2 still works or not.

With the HP wiring harness in place, take a 1/8" to 1/8" male to
male audio cable. Plug it to the microphone jack on the front of
the computer. Touch your finger to the tip of the exposed 1/8"
plug. Is the hum picked up ?

You could also do testing like this, by connecting a line level
audio source to the microphone jack. But the hum test is a bit
safer, as there is no risk to your line level audio device.

If you can pick up hum, then the next step is verifying the electret
voltage on the microphone ring contact. Assuming the mic is in fact
an electret, and not a piezo or a dynamic (magnet plus coil) microphone.

There is some trivial on microphone powering here. "Sound Blaster way"
describes what is typical on AC'97.

http://www.epanorama.net/circuits/microphone_powering.html

Paul
 
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