Following
@NZ8N - his Lead...
This is for the Uniden made style - PC-417 board.
Since your photo has what looked to be a earlier KEPC board - they "kept" Unidens' style of layout using the Hand-Drawn or "analog lazy-wander" of foil traces. The above schematic - I wanted to point out several things.
L16 drives BOTH RX and TX modes. So IC2 being the TX Mixer, may be at fault but then you have other work to do.
You should have signal ALL THE TIME on TP3 - only it shifts 455kHz when you switch between RX and TX.
IC2 can produce work, but the way that the Band Pass Filter in L18 is, may be more of a problem than any 7310 Mixer.
L18 is pretty stringent on what must work for it send any signal to L17.
So let's look at logic.
If you have RX receive, TP 3 shows 16MHz in RX mode, but in TX mode it fails - then a test that the PLL produces to self-check itself - is not being met.
That is where D12 and D18 play a role in helping the PLL do a self-check and make sure that it is producing RF.
D18 goes to the RX side, where the radio uses it's 10.240 clock, used to "down mix" the 10.7 IF - AFTER CF-2 - it should be 455kHz and doesn't need much of a signal to rectify - so it sends it thru D18 back to the PLL when the PLL is in RX mode - there is enough of a signal present so it stays "in lock" and RX works.
But D12 needs the 16MHz with the 455kHz "shift" missing (straight up 10.240 and 16.945 = 27.185 / Channel 19).to work with the 10.240 present at the main Clock back at the PLL - so it "looks" at Pin 7 of the IC TX Mixer, if you are not getting a strong signal - check the slugs and make sure nothings skewed or out of the ordinary at L18 - that is a dual core "stinker" (as I call it) for if it is not tuned right, the rest of the TX mess won't fire up and work for you - the PLL keeps pulling it down because the L18 is a
very tight filter and even prevents signal passage when the 455kHz Shift exists.
At the PLL - Pin 4 is where this signal arrives, needs to be about 6 to as much as 7 volts to tell the PLL to work. If it (signal from either Mode RX or TX) is not there - The PLL "stops".
At PLL's Pin 8 - there should be NO voltage present in RX, but 7~8VDC when in TX - Refer back to
This posts' Voltage Chart.
So Check the T/R pin on the PLL too - if it's not shifting - the PLL won't lock it in and put on the RED TX light and show RF power.
IC 2 even if it's not "right" you'll see something at D12 .- Because L18 it seeing 10.240 and 16MHz at TP3 - it's using TR16 to "turn on" then the Mixer works - so check TR16
AGAIN - make sure you're sending the Mixer 8 volts so it can turn on and produce the 27MHz for the rest of the strip.
Even if IC2 fails, it's when you don't have TX and yet you have a RED LED - THAT is you need to worry about IC2 and following TX strip down stream having bad parts.
Now, your message sounded a little confused, so let's stop here and I'll let you explain the rest...
