Examined, in the absence of sound speaker with strong noise, when the sound system, forced to switch to the 6. OM and then switch back to 6.5 M, sound sometimes also can return to normal. In this process, the image is always normal. 43Rservice manual download site
 43Rservice manual download site
Image is normal, the high-frequency head and into the channel, normal fault in the audio circuit, the audio formats forced to switch to the 6. OM and then switch back to 6.5 M, sound can be back to normal, and there is no sound when the speaker has very strong noise, which suggests that the machine's sound system switching circuit fault. The machine's sound system switched circuit as shown in the figure below. 43Rservice manual download site
 43Rservice manual download site
 43Rservice manual download site
When failure occurs, measured the CPU audio formats switch side (15) (foot) voltage is normal (high level), measured Q221 base voltage is normal (high level), but measured Q224 Q223 e - b voltage and normal large difference. After shutdown, and remove the Q224 Q223 check, all normal. Measuring X221 again, found X221 end leakage and unstable, replaced and troubleshooting.43Rservice manual download site