Panasonic TC - 29 v30r color TV audio distortion, and with a crackle, small volume and fault maintenance methods |
| Time£º2014-05-26 10:16:37 Source£ºNetwork Author£ºUnknown Clicks£º1391 |
|
4wrservice manual download site
4wrservice manual download site
V board is a separate circuit board, erect E plate on one of the main board, the installation position of inconvenience charged to measure. To avoid maintenance detours, before to remove the V board and carefully analyzed the V board the function of each connection terminals, found that in addition to the basic circuit, signal input, output, and besides, there are the V2 terminals (1) feet for headphones mute function (with headphones to use the headphone jack linkage switch closed sound of the bass boost function), (4) feet for shutdown mute control, (4) feet for the subwoofer volume control (connected to the volume control level from the CPU, the flow of ascension bass linked with volume, such as loudness control), 6 feet to the stereo mode control (CPU output corresponding stereo mode control voltage, by controlling the feet high and low level change to realize the "standard", "music" and "speech" selection and control of three kinds of audio). 4wrservice manual download site
4wrservice manual download site
After the V2 and the feet to measure dc voltage, found 3 feet is 0.78 V voltage (the voltage shall be the normal work of the foot 0 V), oscilloscope measurement with a whopping 0.8 Vp - p interference signal. Trial was taken to the foot of short circuit, fault disappear. Thus proved that the cause of the problem is introduced by the end of the jamming signal destroyed the normal work of the V board, V board itself, in fact there is no fault. 4wrservice manual download site
4wrservice manual download site
V23 feet and shutdown mute circuit connection, see this part of the circuit shown in figure 3, its working principle is: the normal work, by the deputy sent 8.5 V dc voltage E18 switch power supply terminals, after R2424 current limiting, D1225 voltage stability for b very Q2429 about 7.3 V voltage, the voltage at the same time the D2429 C1230 charging, Q2429 voltage slightly higher than b e at this time, Q2429 in off state. When using the switch on the television to cut off the ac power, deputy switch power supply also stop work, E18 feet disappear terminal voltage of 8.5 V, the voltage on the C1230 Q2429e, discharge, b Q2429 conduction, the voltage to the V23 C1230 was beyond cure, the voltage in V board mute control triode conduction, thus cutting off the V13, 4 feet of audio signal output, avoid the shutdown appear the noise of the moment.
3 Home Previous 1 2 3 Next Last |
|