I have a CZH-05B FM transmitter. It recently went low power. It will transmit but not more than 20ft. I looked in and found an over heated resistor, maybe two, they are close together, a shorted transistor and a
9 volt regulator putting out 10.8V. I made an assumption that the output transistor was OK since it did transmit, and these parts were in the predrive circuitry. I ordered the parts, installed them and not much change in the signal, I think there is a little more output but it's still not right. So I opened and checked the 9v regulator output. Hmm, it 11.x volts output. The part I removed is labeled 78L09, it is an sot89 part. The part I order is the same. The part I got is labeled 8H612. I'm not sure it is the right part. I have searched for an 8H612 and find nothing. The part I ordered is supposed to be a ST Micro part. I don't know how they mark their parts, But I expect it would say 78L09. I will try to call tomorrow and verify. uh, Monday.The second problem, I should have checked the output transistor, it is shorted. The part on the transistor is K2 092, Marked K2 and then under that is the 092. I have a second unit that has the output transistor marked K2 021. These are surface mount transistors, I can not find any information on these transistors.
Help with either problem appreciated. Mikek