Dear group,
I have this one-chip china-made auto-scan FM radio which has a problem. It has a "SCAN" and a "RESET" buttons on it. The scan button is used to tune and lock to a station. Another push on the button would step it to the next higher station. The reset button is used for reseting it back to the lowest band again. It was able to receive frequencies from 88MHz up to 103.3 MHz but not able to detect anything above 103.3 MHz. I know there were at least 2 stations above 103.3 MHz but I could never receive them.
The fault was there when I bought it new. As the set is very simple and it was made almost identically to the datasheet as shown below. The block diagram and the surrounding components are on Page 2 of the datasheet. The audio part is just 2 NPN transistors cascaded together to drive an earphone.
The datasheet is as below, just click on "data sheet view"
Would someone be kind enough to just take a look and teach me which component might have turned bad and caused the above problem.
Thanks in advance and best regards.
Allen