Check the video signal with an oscilloscope and found that the image path Q4006 (MSB709, as chip components, PNP tube) and resistor R3904 damage. Try a 9012 instead of MSB709, three legs bent at right angles welding, using a 75Ω 1/8W resistor instead of R3904. Energized, AV and RF outputs are the image appears, but still no sound.zfzservice manual download site

    Without accompanying audio heads may be due to damage, poor head amplifier, audio switching circuit is not normal, etc., prior to the present embodiment failure should AV output audio path. After investigation, the head is not damaged, the head amplifier is also normal. Remove the audio switching circuit boards VEP04361K, found IC4501 (XLH7770KS) has burst, judgments are caused by overvoltage overcurrent.zfzservice manual download site
 zfzservice manual download site

    The figure shows the principle of the aircraft, IC4501 90 feet for the power input voltage is 5V. Regulator circuit the voltage generated by the Q4501 (2SD655) and IC4501 internal composition of the 12V voltage buck derived. Issue should be out on the Q4501, the road test its c, e electrode resistance only about 20Ω. Under the tube smaller power (from the exterior look should be medium power tube), on which the pressure drop of 7v, so long working hours (local time singing karaoke 0K long and burned) case, Q4501's c, e breakdown between (not completely short-circuited), resulting in IC4501 supply voltage rises to burn. The price is very expensive due to the manifold, and not just for Ic4501 Q4501, it is necessary to improve the circuit.zfzservice manual download site

    After careful analysis of the circuit that can be used instead of the original 7805 voltage regulator circuit, the input interface Q4501 7805 of c-pole output connector e pole, with the circuit board connected to ground, replace the IC-4501 power test machine, sound completely normal, so far Failure to completely ruled out, but also proved to be successful circuit improvements.zfzservice manual download site