N-Bomb said:
I tried plugging in an old set of speakers with a dodgy AC adaptor,
and now the PC won't output any audio... when I try to get it to sense
the connectors, it says failed for all of them. What could be the
problem here?? Thanks for any help
What exactly is a "dodgy AC adapter" ? Are you getting a shock from
the product, implying AC is leaking through to the input side ?
Ideally, amplified computer speakers should have isolated power. Something
like a two prong plug, as that implies the computer will be establishing
the ground level.
All the AC'97 sound reference designs I've looked at, use AC coupling
of the inputs and outputs. The "strong drive" ports, like anything intended
for driving headphones, might use 100 microfarad (uf) capacitors for that
coupling, while input channels or weak (600 ohm) outputs use 1 microfarad
caps (likely ceramic). If a high DC voltage is applied to a large capacitor
like that, it could be the inrush current could fry the AC'97 chip. If a
high AC voltage is applied, you could exceed the breakdown voltage of the
chip pins.
It could be, that somehow your speaker setup has driven current backwards
into the jacks on the motherboard. If there was DC voltage greater than
the breakdown voltage on the caps for example.
Looking at the ALC850 datasheet, it is unclear how their jack sense
works. The registers in the chip consist of:
MX66 Sense Function (can be set to sense tip or ring contact of 6 stereo jacks)
0h: FRONT-OUT (pin-35/36)
1h: SURR-OUT (pin-39/41)
2h: CEN/LFE-Out (pin-43/44).
5h: MIC1 In (pin-21)
6h: MIC2 In (pin-22)
7h: LINE In (pin-23/24)
MX68 Sense Function Information (indicates sense cycle worked or not)
Information Valid bit, IV
0:After a sense cycle is completed indicates that no information is
provided on the sensing method
1:After a sense cycle is completed indicates that information is
provided on the sensing method
MX6A Sense Detail (sense cycle identifies device plugged into jack)
S[4:0]
For output jacks:
02h: Not specified or unknown
05h: Powered speaker
06h: Earphone or passive speaker
For input jacks:
12h: Not specified or unknown
13h: Mono Microphone
15h: Stereo Line-In
so it sounds like the chip is no longer returning "information valid".
Either return the motherboard under warranty, and get it fixed, or
simply plug in a separate sound card and use that. I doubt the problem
is software related, but if you want, using Add/Remove, uninstall the
software, then reinstall the software package. If it still isn't
working, it is likely some fried hardware.
To know more, you would need to see what voltage shows up on the 1/8"
stereo plugs on your "dodgy" speakers, with respect to the ground level
of your computer case. Using a voltmeter, measure from computer chassis
to the tip and ring contacts of the speakers. Try the voltmeter on the
high AC range, and then switch to high DC range, and measure again. (You
want to use a high range, so the voltmeter isn't damaged.) You might
get some idea of what is leaking out of the speakers plugs, waiting to kill
whatever it is plugged into.
Paul
