Whatever. I'm trying to get it fixed and your asinine comments are Unwelcome. Idk why some of you guys have to be so rude to those of us that are not 60 some year old techs!!
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Trc 449 no transmit
- Thread starter Staybolt
- Start date
Troubleshooting is a stepwise process, whether it's your daily driver that won't start, or a radio that won't transmit.
You will usually find that the first few things you check are not the cause of the trouble. Once you find enough things that aren't broke, the process will eventually lead you to what really is broke.
I'm a bit surprised nobody asked if the relay goes "click" when you key the mike. Don't laugh. Unless I'm looking over your shoulder there's no way for me to know.
Sometimes the first thing you check turns out to be causing a fault. More often, you'll rack up a list of things that aren't broke before finding the root of the fault.
The next thing I would suggest is to tune in a second radio onto the same channel as the TRC449. Plug a spare coax jumper into the monitor radio. Thread the outer sleeve of the coax plug back onto the cable leaving the center pin fully exposed. The pin at this end of the jumper is now a "sniffing" antenna, to see if a weak signal is being generated inside the radio.
If you can't hear anything in the monitor radio, don't waste time looking at the transmitter's power stages. Even if they're working, they have to have a drive signal feeding into them.
And if you do hear the signal in the monitor receiver, see if the signal is stronger near the rear of the radio.
But this is a big dividing line in the radio, just finding out that your transmit signal is being generated at a low level to begin with.
Yes, the final transistor is a common failure. You'll hear advice to just "shotgun" the problem and change it. But if it has no drive signal feeding into it, that would be a waste of time.
73
You will usually find that the first few things you check are not the cause of the trouble. Once you find enough things that aren't broke, the process will eventually lead you to what really is broke.
I'm a bit surprised nobody asked if the relay goes "click" when you key the mike. Don't laugh. Unless I'm looking over your shoulder there's no way for me to know.
Sometimes the first thing you check turns out to be causing a fault. More often, you'll rack up a list of things that aren't broke before finding the root of the fault.
The next thing I would suggest is to tune in a second radio onto the same channel as the TRC449. Plug a spare coax jumper into the monitor radio. Thread the outer sleeve of the coax plug back onto the cable leaving the center pin fully exposed. The pin at this end of the jumper is now a "sniffing" antenna, to see if a weak signal is being generated inside the radio.
If you can't hear anything in the monitor radio, don't waste time looking at the transmitter's power stages. Even if they're working, they have to have a drive signal feeding into them.
And if you do hear the signal in the monitor receiver, see if the signal is stronger near the rear of the radio.
But this is a big dividing line in the radio, just finding out that your transmit signal is being generated at a low level to begin with.
Yes, the final transistor is a common failure. You'll hear advice to just "shotgun" the problem and change it. But if it has no drive signal feeding into it, that would be a waste of time.
73
Nomad. He said he manually keyed the relay and had RF output, He also stated that the finals were good. So that eliminates the RF chain. Problem seems to be in the keying circuit. It seems that keying the mic is not causing the relay to engage, yet when manually keyed it does and everything down the line is functional. I found his posts a little confusing/contradictory in nature when I read how he could have RF output and then him say he didn't have RF output. I understand now that he only has RF output when the relay is manually keyed and no output when he tries to key the microphone. Just trying to clarify things here. It is a lot easier to troubleshoot a problem if we are all on the same page.
"Tried another mic, nothing. I manually keyed the relay and it does put out power on am so finals are good. It acts like an issue between the mic and keying circuit. Anybody got any ideas?"
"Tried another mic, nothing. I manually keyed the relay and it does put out power on am so finals are good. It acts like an issue between the mic and keying circuit. Anybody got any ideas?"
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You'll never see a better deal on that part. Should probably buy two, just for that rainy day down the road.
73
73
I bought 10 of them a few months back ... just in case they become scarce again.
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Good job. It almost had to be something like that. Looking at the schematic the TX switch on the mic goes to pin 3, pin 3 goes to the CB/PA/MON switch and, assuming the switch is in CB position.... goes straight to the trigger side of the relay.
The hot side of the relay goes straight to the power switch and, if the radio has power, then the relay coil is hot.... not much else to go wrong.
Glad you found it.
The hot side of the relay goes straight to the power switch and, if the radio has power, then the relay coil is hot.... not much else to go wrong.
Glad you found it.