Next test was at pin 4 of the audio chip with a metal probe. I used a frequency counter to check the 10.240. Do you hear a slight signal? Now key the test radio and listen to the rig under test, do you hear anything? does the meter move?įirst test was at pin 2 of the PLL chip. Key the radio under test with the test rig set to the same channel. This is when your test radio comes in handy. I am not just talking about audio, but there is no detectable 27 mhz signal on TX or RX. I still use the basic 29 schematic theme when checking these radios. On the bench at this moment is a Uniden PC 66XL. If the chip is bad it can short the voltage to ground and stop many circuits from running. If all is good you will hear a loud roar you can expect the audio chip is good. Failure of the 10.240 crystal does happen often. If you find no 10.240 check the solder connection to the crystal. When a radio comes in that does nothing but light up, the first thing I do is check the 10.240 mhz crystal oscillator. See, a lot of times with just using what you have the problem may stand out in front of you. If you touch components do they feel hot? And dont forget the test equipment you were born with.ĭo you see anything out of the ordinary like burnt traces, blown components?ĭo you hear anything when you transmit to or from the test rig? a good DVV, frequency counter, watt meter dummy load, and a test radio. But to do this you will need a few pieces of test gear to do so. Instead of going in and shot gunning the problem it would most likely be easier to find out what is working. Or the radio meter moves on receive but you hear nothing coming out, you would check the speaker and the external speaker jack.īut what if the radio has no trans mit or no receive? Or worse yet has neither ? You would start with the simple stuff like checking the mic. Say the radio transmits power but there is no modulation from the rig. It was given to me and I updated it.Ĭool, Well we will get started with the basic stuff this week. Then in the end discuss how to make your own test equipment like using the 29 as a signal generator Just to give the guys that want to learn a bit of a heads up. Post a description of components and what they are. Post a schematic with the various stages marked. What I like to do is start with a chassis like the cobra 29. I see so many folks trying to troubleshoot radios and do not even know where on the board to find the problem let alone on the schematic. There are a lot of folks here full of technical knowledge and I think this would be a good tread to help others that want to know learn and understand what is going on in these little set’s. I have picked up some free time now and it may be something to help those that want to learn. If any are interested I like to start a thread on understanding how CB radios work.
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