No Sound In Panasonic TV Repaired
This Panasonic CRT TV came in for repair with the complaint of no sound. Usually no sound symptom can be due to open speaker, broken speaker wire connection, Mute, corrupted EEprom data, missing dc supply to sound output IC, bad sound output IC and etc.
Once the TV cover was removed, I checked on the speakers first and found both of the speakers were good (have Ohms reading).
Next, I checked on the DC supply to the sound output IC-see the photo below:
On the DC supply side to the sound output IC, I measured and got 21.2 VDC but on the other side of the fusible resistor, I got almost zero volt. This usually indicate the resistor already opened circuit.
Since this is a fusible resistor with low ohm (2.2 to 4.7 ohm), this means something had shorted that caused the resistor to open circuit. Chances is very high the sound output IC was shorted.
When I set my meter to Ohms range and checked on the sound output IC vcc pin to ground, I’d got .001 Ohm which means it had a direct short circuit. This is the reason why the fusible resistor was open circuited.
I replaced both the resistor and the sound output IC and powered it on, I was very happy to hear the sound came back again.
Conclusion- Assuming if there is no short circuit and the VCC pin to the sound output IC measured 21 Vdc, then my next step would be to direct replace the sound out out IC and retest. If still no sound then I will reprogram the EEprom IC.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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