I would follow Evan's advice.? I know the videos you refer to and they are very good. There are 5 (I think) on building the amp and a further "Troubleshooting" video.? You need to follow all the steps in the troubleshooting video as I mention below.
Did you start at the PTT section and make sure that is working O.K. You then need to check what is happening at L9 when switching between Rx and Tx.? That then leads onto Q4... is it being turned on.? Is there a positive voltage on the input of IC1 ??
If you have checked as above then, if there is no 5v output IC1 is not looking good. We don't know if you did the checks outlined above as you stated you checked the input to R10 (I think it's the input you measured) which would show that there is 12 volts there but doesn't tell us if the transistor is turning on and passing that voltage to IC1.
Just to be sure and narrow down what is happening might I suggest....? go through the troubleshooting video again and do the testing at each stage as shown in it. You do NOT need to hook up the QCX.... indeed it would be better if you don't at this stage. Just supply 5 volts to the amp's PTT switch and it would be easier if you could just switch this off and on easily....? I use a press button switch for this. Now you can supply 12v to the amp and by means of the PTT 5v switch you can change between Tx and Rx.? Having got the 5v PTT line set up you can now go through the testing steps shown in the series of videos. You will be switching between TX and Rx as you test voltages at all the places shown in the video. You do NOT want to connect the QCX as you do not need a signal through the amp at this stage. Once you have verified the voltages for Tx and Rx at each stage you will then probably have identified the problem. If everything checks out as it should you may then need an oscilloscope, but you do need to check the DC voltages before you get to that stage.
Make a chart of the voltages as you test each step shown in the videos, have two columns one for Rx and the other for Tx voltages. You then have something to go on and can compare with the same test points on the videos.
Please attach a dummy load while testing just to be on the safe side. Probably don't need it as you are not putting a signal through the amp and amplifying it but it won't hurt to attach one anyway.? Once you have followed the steps in the video about troubleshooting then you should know a good bit more about the amp than before.
In a nutshell...?? provide 12v or so to power amp. Arrange 5v to the PTT to switch amp between Tx and Rx. Follow the troubleshooting video. Do NOT connect up the QCX.
Hope that helps.
Reg??????????????????????????????? G4NFR
