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A7V8X-MX-UAY 5 VOLTS ON SPEAKER?
In article , oostrich
wrote: many thanks Dave for the reply, a bit strange the 5 volts, but anyway do you have any idea why the speaker may not work? i have tried 2 speakers, none work. maybe this mb is different?, cheers oostrich I downloaded another copy of the manual, and I see a piezoelectric buzzer in between the area bounded by the CHA_FAN header and the PANEL header. Maybe the buzzer is supposed to function instead of a speaker ? Is that buzzer actually present on your motherboard, or is the picture in the manual incorrect ? Considering the drive circuit for the speaker (assuming it is installed and present on the motherboard), it is pretty hard for it to be damaged. The only failure mode I can think of, is if you accidently shorted the +5V connection to an adjacent GND. That might draw enough current to burn out the connection to +5V. Apparently, motherboards don't have polyfuses on that pin. To test that theory, I'd unplug the computer from the wall, then get an ohmmeter and check the resistance between the +5V pin on the PANEL connector, and a +5V pin on some other header or connector. For example, one of the pins on a disk drive power plug goes to +5V, and should read close to zero ohms between a power plug and that +5V pin on the PANEL connector. The drive transistor might have failed - it should be a three legged plastic device in the vicinity - but it would be hard to test. In the figure below, I'd touch a 1K ohm resistor from +5V to the base (B) lead on the transistor, then listen for a click in the speaker, as a way to test that the transistor works. +5 / | __/ |_____| _____ SPKR | |__ | \ / \ \ 33 ohm / resistor \ | | C B | / _______|/ 2N3904 |\ | \ | E | ----- --- GND - The 33 ohm resistor shown in the circuit, is a current limiter, and that thing should have a 1/4W to 1/2W power rating (depending on whether the designer planned for a 32ohm speaker, or planned to make the circuit bulletproof against the speaker being shorted). I don't see any suspiciously large resistors in the area of the PANEL connector, to help identify where the drive circuit is located. As you can eyeball the board, you may be able to see the copper track that connects to the corner pin labelled "speaker" in the manual - if you follow that wire, it should take you to the current limiting resistor and the driver transistor. Paul On Tue, 30 Mar 2004 11:38:27 +0800, oostrich wrote: on page 1-22 in the motherboard manual it shows there is +5 volts on the case speaker connector. why does it need 5volts, case speakers dont need this voltage. my internal speaker does not work when connected to this connector, my case speaker has 2 wires like 600 million other case speakers out there , why the 5 volts? thanks oostrich |
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