This TV was brought in my shop with the picture ok but the sound was not stable…sometimes good and other times not.
I opened the set and went straight to the speaker (power off and power cable disconnected from the power outlet).
Checking on the speaker label I noticed the speaker was rated 8 ohm and a quick test with my ohmmeter got 8 ohms…this confirmed to me that the speakers are okay and therefore I should look elsewhere for the problem.
So the next hypothesis considered for checking is the sound amplifier ic and since I did not have the circuit diagram of this TV, I decided to look up for the sound amplifier ic, To know which is which I followed the speaker wires backward from the pins of the speaker to the main pcb and followed closely the PCB lines and this directed me to an ic TDA 7245.
I did a Google for this IC TDA 7245 for the datasheet and here what I got.
Looking at the circuit you can see pin 3 is very important because it is the power supply pin. I set my meter on 100 VDC range and did a voltage testing on this pin with my meter red probe on the pin 3 and black on cold ground.
To my surprise the Voltage was well within my expected because from the datasheet I was able to see that this IC needs a working voltage between 14 VDC minimum and 30 VDC maximum.
Up to here things are ok, now what else? I decided to check for the signal output for the presence of a signal using a scope and if found no signal and I concluded that the IC TDA 7245 must be the culprit.
Below you can see the pin connection of this IC
I replaced the IC with a new one and after applying the Power I loved what my ears heard…very nice sound…
This Report is brought to you Courtesy of Mr. Beh.
A renowned Technician of all time
City: Tehran Country: Iran
Mr Beh can be contacted directly at email: email@example.com