I explained this on the wrong header. My friend blew the final and I have replaced it with a new one. Also replaced blown power diode and have unit powering up and functioning except....1/10 of a watt is the only reading I am getting on transmit (Should be 5 to 15 watt). I cannot find any board layouts to determine what is what so, I am flying blind. Bias resistors or electrolitics????
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Re: No transmit after blown final was replaced.
I tried to answer this the first time you posted :). If the finals got burned that bad I found that the bias resistor sometimes will get a burned foil and not make good connection. Also 1/10 watt sounds like the driver isn't amplifying from the buffer. Might want to check for burns on the foil all around the final stages, including where the antenna connector mounts to the board. Don't believe the caps are blown but as a last resort.... Its really hard to troubleshoot without the radio on the bench . Good luck. Tom
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You have to press the transmit button to get the radio to send a signal that you can calibrate the SWR meter to. If you are pressing the transmit button and nothing is happening then it could be a blown final transistor, a bad switch, bad microphone connection etc.
There is a good chance you could have blown your final transistor. It could also be something is no malfunctioning in your mic. Is it on frequency? Hook it up to a frequency counter and make sure channel 19 reads 27.185. If it is your final transistor it blew for a reason. Most likely it got hot from a high SWR. 1-1:5 is the goal and no higher than 2. If it he SWR is higher then 2 the check your coax cables and adjust your antenna. Good luck.
Firts you have to check for carrier.For this you need an swr meter.2) Check continuity between the pl259 tip and antenna.3) Check for modulation (voice) if all of the above are OK. 4) Check if your display changes to transmit when you press the mike. IF all fails,then try another mike.
I am assuming you have called out for a radio check and not gotten a reply, or even better tested it with friends radio. Just because the meter doesn't mover doesn't mean that its not transmitting.
So as long as you tested it with another radio, and it is not transmitting it could be any number of things. If you have never had antenna tuned so the swr is low, or your swr was high for a long time, your final transistor is most likely blown.
TX switching transistor could be blown, trace could be gummed up.
If your ant light is coming on, the is a problem with your antenna. Could be disconnected, and that can lead to a blown final.
At any rate, your problem most likely requires a tech. Take it to a repair shop.
well that leaves 2 mor parts the transmit final and the current resistor these have straight 12 volts applied when the radio is turned on . if you look at the final it will be burnt or blown apart on the heat sink. replace them and you shoul be up and talking again.
Initially, pls confirm that there is modulation (transmit audio). The reason I asked is if IC4 (TA7222P) is blown, then the radio would have no audio amplifier which would explain no receive audio. Additionally, the final and pre-final (TR15 & 15) gets is modulated TX+12 through D8 from T1 which in turn is the output of IC4 through C48.