The PA final device is a Motorola SRF7042 ldmos. Under the main pcb you’ll find many other SMD parts including the CML chip that handles all the audio processing. The early radios have an issue of exceeding the CML vcc maximum voltage of 4.6v as they run it at 5 volts. A simple addition of a diode, 1n914, in series will lower this to a safe value. Otherwise, the CML chip will fail locking up the host cpu causing a scrambled led display. I repair these radios and this is about the only issue they ever suffer. Very robust and reliable. We run many as repeater and link radios. The whine or buzz you hear may be a result of the CML operation out of its limits. 73, Dan N5MRG
Really nice video. This led me to make a video for the off-road community on a re-branded version of the TYT. I appreciate the effort and technical explanations of the components. Thank you for posting this.
just want to aid to your slight "buzz, humm" ( if you have any other electrical devices), I find tube lights, clock radios to be my problem being to close to the radio, power leads, antanna could pick up line cycle buzz, 73's ...cheers
Just blew a fuse installing my th9000D... and, I believe I crossed the 12V + and - to cause the issue. Now, I continue to blow fuses when trying to power up the radio on ANY of my 12V sources. As I understand it... there's an internal protection diode. Do you know of such a thing? Where would I find it to replace it???
tyt 9000D, I have 2mtrs and 70cm units, this model looks more like 70cm ver, I have my 70cm open atm' a fuse blow 'power crossover' and now no TX I just removed protection diode still no TX all volts are good (12.4 volts on output of trans in this good or bad
Anyone putting the 9 pin serial in for a remote-base radio or repeater the cos or cor output line is always present when receiver radio is unsquelched and receiving any signal so if you put in ctcss decode the radio still has a Cor output upon any signal (useless) for tone decode you will have to add a t32 tone PCB to lock up receiver on repeater input. There's always interference or birdies, qr, ect getting into your input so that's the deal with DB9 kit.
Have you built a repeater using these radios? Asking because I’ve ordered the radios and interface cables. I have outboard squelch boards but I’d rather not need to use one. Tnx in advance
@@sdjakeblues You will find that your radios will not power up in "on" condition after a power outage. There is a connector on the back for "external power" which appears to be an ignition sense port. I think you could wire it to 12v permanently but the small barrel connector is difficult to find. It appears that TYT doesn't really sell that cable. When I made my own, it didn't work. Did you make the repeater and did you just live with the fact that the radios don't stay on?
