I'll paste in some information below that is one explanation for those symptoms, but I must emphasize that it is not necessarily the cause of your problems on your particular computer.
An explanation for this combination of symptoms
* Speakers don't work * Headphone jack does work * Reinstalling audio driver does not help * Audio test in Dell Diagnostics passes
The Dell laptops like yours with a Sigmatel 92xx audio chip utilize IDT's Universal Jacks technology, which is somewhat complicated. In addition to the usual mechanical parts, the jack also uses current & impedance-sensing techniques to trigger software configuration and switching (to send the audio signal to the speakers). So there are three areas of potential failure: mechanical, electronic, and software. Sometimes, a little very gentle wiggle of a plug in the jack will get it to resume normal functioning, at least temporarily. There is a sensing pin in the jack (Sense_A pin) that is used to detect the presence of plugs and it can be the cause of failure to trigger the software switching.
Normally the audio test in Dell Diagnostics would confirm that there is a hardware problem, but the Universal Jacks can cause a false positive result in Diagnostics. That is because Diagnostics operates in DOS, outside of Windows, so a Windows software misconfiguration is irrelevant to the test even though in this case it is caused by hardware. So the audio test can pass in Diagnostics, correctly signaling that software configuration is the immediate cause of the problem, but missing that a hardware problem, the bad jack or sensing pin, is the root cause. In these instances the only reliable diagnostic procedures are to try a new motherboard or to use PC Restore (called Factory Image Restore in Vista) to restore the computer to its original configuration as shipped from the factory. If the speakers still don't work after PC/Factory Image Restore then there is definitely a hardware problem even if it passes the normally infallible Dell Diagnostic audio test.
Having said all that, I'll backtrack a little because the other symptom you report that the audio has "disturbance not clear" is a symptom of mechanical failure within the jack, not the sensor pin. Either way my bet is on the jack.
Thanks a lot for your inputs .I will see if I can restore it back to some old setting ,though its 2 years old laptop.Is there any way to simply replace the jack or motherboard on the whole needs to be replaced.
The jack on most of the Dell laptops including the 640m is not a replaceable part in the sense that you can buy it and put it in, so for units that are still under warranty the entire MB gets switched out.
Jim Coates
4 Operator
•
13.6K Posts
0
October 29th, 2008 12:00
I'll paste in some information below that is one explanation for those symptoms, but I must emphasize that it is not necessarily the cause of your problems on your particular computer.
An explanation for this combination of symptoms
* Speakers don't work
* Headphone jack does work
* Reinstalling audio driver does not help
* Audio test in Dell Diagnostics passes
The Dell laptops like yours with a Sigmatel 92xx audio chip utilize IDT's Universal Jacks technology, which is somewhat complicated. In addition to the usual mechanical parts, the jack also uses current & impedance-sensing techniques to trigger software configuration and switching (to send the audio signal to the speakers). So there are three areas of potential failure: mechanical, electronic, and software. Sometimes, a little very gentle wiggle of a plug in the jack will get it to resume normal functioning, at least temporarily. There is a sensing pin in the jack (Sense_A pin) that is used to detect the presence of plugs and it can be the cause of failure to trigger the software switching.
Normally the audio test in Dell Diagnostics would confirm that there is a hardware problem, but the Universal Jacks can cause a false positive result in Diagnostics. That is because Diagnostics operates in DOS, outside of Windows, so a Windows software misconfiguration is irrelevant to the test even though in this case it is caused by hardware. So the audio test can pass in Diagnostics, correctly signaling that software configuration is the immediate cause of the problem, but missing that a hardware problem, the bad jack or sensing pin, is the root cause. In these instances the only reliable diagnostic procedures are to try a new motherboard or to use PC Restore (called Factory Image Restore in Vista) to restore the computer to its original configuration as shipped from the factory. If the speakers still don't work after PC/Factory Image Restore then there is definitely a hardware problem even if it passes the normally infallible Dell Diagnostic audio test.
Having said all that, I'll backtrack a little because the other symptom you report that the audio has "disturbance not clear" is a symptom of mechanical failure within the jack, not the sensor pin. Either way my bet is on the jack.
Jim
udayverma
3 Posts
0
October 29th, 2008 15:00
Jim
Thanks a lot for your inputs .I will see if I can restore it back to some old setting ,though its 2 years old laptop.Is there any way to simply replace the jack or motherboard on the whole needs to be replaced.
Thanks for your time.
Jim Coates
4 Operator
•
13.6K Posts
0
October 30th, 2008 00:00
The jack on most of the Dell laptops including the 640m is not a replaceable part in the sense that you can buy it and put it in, so for units that are still under warranty the entire MB gets switched out.
Jim
udayverma
3 Posts
0
October 30th, 2008 05:00