Cool, Well we will get started with the basic stuff this week.
Some things are easy to fix. Say the radio transmits power but there is no modulation from the rig. You would start with the simple stuff like checking the mic. Or the radio meter moves on receive but you hear nothing coming out, you would check the speaker and the external speaker jack.
But what if the radio has no trans mit or no receive? Or worse yet has neither
Instead of going in and shot gunning the problem it would most likely be easier to find out
what is working. But to do this you will need a few pieces of test gear to do so. a good DVV, frequency counter, watt meter dummy load, and a test radio. And dont forget the test equipment you were born with.
Your senses.
Do you
see anything out of the ordinary like burnt traces, blown components?
Do you
smell anything burnt?
Do you
hear anything when you transmit to or from the test rig?
If you
touch components do they feel hot?
Do you
taste ..opps, we want go there
See, a lot of times with just using what you have the problem may stand out in front of you.
When a radio comes in that does nothing but light up, the first thing I do is check the 10.240 mhz crystal oscillator. Lots of time I fine the problem there. If you find no 10.240 check the solder connection to the crystal. Failure of the 10.240 crystal does happen often. If all good there go to IC 4 pin 4. This is the Audio amp. pin 4 is input and pin 9 is output. With a metal probe touch pin 4. If all is good you will hear a loud roar you can expect the audio chip is good. If the chip is bad it can short the voltage to ground and stop many circuits from running. The voltage to the TA7222 is on pin 10.