While I'm still waiting for my new caps to arrive I have read this string over again. I see where I said I was going to wait to lift D25 until I had it recapped. Since I'm still waiting I have put in a new 10.240 Xtal, that didn't change any symptoms but I did lift D25 and it did restore TX LED function. Can you help explain what exactly taking the diode out actually did? Also I did hear and it was loud some type of noise not signal then it went away thru the external speaker. Almost like some capacitors were charging then stopped. Hearing this I'm assuming the audio amp is working or did it just blow up..lol ???? But anyway after hearing this when the noise stopped I immediately checked the XT function again. I thought something went horribly wrong but it still lit the XT led but also introduced some rf that my other radio picked up but no power out on the meter. Just trying to give you as much info as I can.
Just for info and some help - to help you understand.
You remove the TX "block" Diode. That is for the purpose to prevent - that, which is what you experienced.
When the PLL is out of lock, you don't know what channel you're on, or if you're even in the ballpark. You heard the noise because of this free running out of lock signal - because you took out the diode used to detect and PREVENT this from happening. The PLL is (trying to) doing it's job in keeping the radio in and on, the CB band.
This board uses a PLL system that runs ABOVE the frequencies of the CB band, but then "divides" this higher frequency (it) down using a SUBTRACTION (a method of mixing) and they use Lo-Pass filter methods to remove that 35~36MHz frequency the PLL uses to track itself - from leaking into the output of this section - it is otherwise a typical IF mixer from other CB's the use 16MHz IF (Below the CB Band of Frequencies')
You may want to look into Heterodyne and Images - these terms are used interchangeably when it comes to understanding the process of converting a higher RF-based signal into an IF process-able means to pull out those stations on your channel or frequency of choice
So if you need help - find your "Calculator" on your keyboard of Windows PC or your Phone and do some simple math - remember the 34~35 MHz issue, and subtract 27MHz - you'll see something close to 7.8 or 8MHz - look to your schematic and you'll see the radio (along with others similar) really have several different oscillators, one free runs with the PLL (your Tripler uses X3 ~11.25MHz Xtal) and 10.240 BASE (PLL) Xtal and makes that 34~35MHz mess you're experiencing - but needs to "lock it in" and then REMOVE some of it by mixing in your 7.8MHz at X4 - or uses the X3 one to do the same thing - only in steps of your IF CONVERSION it processes. for the RX mode, does it use a different process of applying the higher MHz signal to the 27MHz, leaving you with two images, one higher and way too high in MHz to be useful - so it's filtered off, the other lower Frequency image (Below the CB band), is then applied to another filter to clean it up and then amplify it. This process is the Conversion.
The X3 and X4 then help you obtain 10.240 standard IF and the 455kHz after it passes thru using X3 and X4 to obtain these IF frequencies.
Why so much into the IF part? Well, you can use a simple crystal radio "kit"...to receive...
Please don't...
Basic way to think this...
Generates 35MHz (approx. to save bandwidth) then uses it, at the PLL's choosing (locking in) of this 34~35MHz also uses 7.8MHz to SUBTRACT this 7.8MHz - from your 35MHz - to attain your selected channel in the 27MHz band.
So what we're trying to do here, is steer you in a direction of progress, is to make the PLL "lock" the 35MHz signal using it's own loop into the foray - to lock onto a precise frequency to obtain the needed images that IF can process.
The Channel Selector programs the divisor thru pins, to parse down the 35MHz into a working signal the PLL uses to "track" and control the loop - once in control - the PLL can declare "lock" and allow the Transmitter side to work.
Clear as mud right?
