New member here. I was on a CB forum once upon a time in the long ago, but can't for the life of me recall which one. I'm more of a mechanic and like having CB's in my pickups, but it's been awhile since I've installed one. A little info on the setup... A used Cobra 148 GTL that I got while helping friends clean their deceased uncle's place (along with 5 other various mid sized units) with 75-ohm cable and dual Firestik antennas mounted high on west coast mirror struts, 4-pin Diesel noise canceling mic to right angle adapter to 4/5 pin adapter. I haven't yet looked at the back of the CB to see where it was made, but it has the 5 pin mic jack on the left side. This is my first SSB unit (Uniden PC78XL in the retired truck on the same setup). Here's where my questions come in. First, it seemed to operate fine. No talkback, which after researching the unit I expected, but the needle in the meter was stuck and the RX/TX light would only light up a dim red when the mic was keyed (no green for receive). I ordered a new meter, meter bracket (old one was brittle and cracked in 2), and 3 pin dual color LED for the RX/TX light. After installing these, I put the radio back in the truck to tune the SWR and found I soldered the meter backwards. Yesterday I corrected my mistake and reinstalled the radio to tune it again. Got the SWR set and parked. Later in the day, the right angle adapter for the mic cord arrived, so I installed it, keyed up and got screeching feedback! It took me a minute to realize that the radio had suddenly developed talkback! I removed the right angle cord adapter to see if there was a change and there wasn't. When I was working on the radio, I looked to see if it had any extra added on boards for mods for talkback or a resistor bridging connections at the back for a universal talkback mod and found nothing of the sort. I did this because there had been holes of 2 different sizes drilled in the underside of the case for, I'm guessing, switches and pots. While still toying around with the radio in the truck attempting to get a radio check unsuccessfully, I noticed that the Brit/Dim switch didn't dim the lighting and that the Hi/Lo tone switch seemed to change something else, like channel? I listened to someone talking with it on Hi and when switching to Lo tone there was no longer anyone talking at all. So, before I pull it out of the truck again and start taking pictures of the inside of the radio, what are some common mods that use these switches that could have been done to this unit? If something is useful, I may keep it, but I'd like to restore the switches to original function if not, or at least know what they are doing!