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Cobra 2000GTL frequency adjustment
- Thread starter Adamf
- Start date
Maybe I missed it but does the frequency change at all when the clarifier is moved? I don't care what the freq. is just whether it changes or not. If it does then the varactor diode D35 must be getting voltage and is working. If it does NOT change then look for voltage on the cathode of D35 shown above. The best place to look is where R149 and L27 connect together.Also what is the voltage at that point? It may be too low. It should vary from almost nothing to about 8 volts or more when the clarifier is moved.
the only reason i can see someone trying to tie the clarifier in to the channel mod is in an attempt to get the zero channels, such as 27.420 etc... by switching in a certain resistance value in certain switch positions in order to vary the clarifier by 5khz.
That is my guess as to what all those other components and wires are about.
Adamf, i don't want to leave you completely in the lurch with a 2000GTL that you can't use, so i will make this offer to you.
If you feel like you want to dive in and try to get this thing back to stock, i will attempt to help you, either here or in a private conversation (i prefer the public forum so others can help or be helped by it also) BUT! you will have to do most of the leg work.
For example, we would want to remove the channel mod first, but i can't type up the whole procedure for removing the specific mod you have, as i haven't seen it done like this before.
You will have to ask me specific questions, and i will try to answer them.
thats the best i can offer in this situation, and i only offer it because i hate to see someone excited about the hobby with a radio that they can't use. This will take some time, so don't expect that you will have it up and running this month.
LC
That is my guess as to what all those other components and wires are about.
Adamf, i don't want to leave you completely in the lurch with a 2000GTL that you can't use, so i will make this offer to you.
If you feel like you want to dive in and try to get this thing back to stock, i will attempt to help you, either here or in a private conversation (i prefer the public forum so others can help or be helped by it also) BUT! you will have to do most of the leg work.
For example, we would want to remove the channel mod first, but i can't type up the whole procedure for removing the specific mod you have, as i haven't seen it done like this before.
You will have to ask me specific questions, and i will try to answer them.
thats the best i can offer in this situation, and i only offer it because i hate to see someone excited about the hobby with a radio that they can't use. This will take some time, so don't expect that you will have it up and running this month.
LC
Looking at the mods, it does appear as though LC is right, looks like the extra channels and clarifier are tied together to get into the "half" channels. Interesting way of doing it. I think we need to get it back to stock 40 channels for now, and get the clarifier back to stock, then "re-modify" the clarifier and PLL for the extras.
Like LC, I can also assist in the process, if you are willing to do the actual soldering/grunt work. I can advise from there.
~Cheers~
Like LC, I can also assist in the process, if you are willing to do the actual soldering/grunt work. I can advise from there.
~Cheers~
Anytime, LC!! 
I had a laugh for sure.... but I've literally seen just about every kind of wire used for mods in CB radios.... from magnet wire all the way up to 6 gauge mega cable. Yes, I really mean 6 gauge. Don't see magnet wire used all that often tho... it's one of the more interesting mods I've seen too. Also noticed how the wires are soldered directly to the PLL on the component side of the board, not the solder side. That also made me chuckle.
~Cheers~
I had a laugh for sure.... but I've literally seen just about every kind of wire used for mods in CB radios.... from magnet wire all the way up to 6 gauge mega cable. Yes, I really mean 6 gauge. Don't see magnet wire used all that often tho... it's one of the more interesting mods I've seen too. Also noticed how the wires are soldered directly to the PLL on the component side of the board, not the solder side. That also made me chuckle.
~Cheers~
Could had been a mod gone wrongAnytime, LC!!
I had a laugh for sure.... but I've literally seen just about every kind of wire used for mods in CB radios.... from magnet wire all the way up to 6 gauge mega cable. Yes, I really mean 6 gauge. Don't see magnet wire used all that often tho... it's one of the more interesting mods I've seen too. Also noticed how the wires are soldered directly to the PLL on the component side of the board, not the solder side. That also made me chuckle.
~Cheers~
I'll do my best to try and help on this fix-up too. It would be better if someone could post the REAL Cobra 2000 Service Manual. The one on CBT and the one posted by Sonoma are just a Cobra cover with a reprint of the material in SAMS #251. The real manual would have wiring diagrams, board layouts, circuit descriptions, etc., which would make putting everything back to stock much easier. I've been searching for the real deal, but haven't had any luck yet. I'll keep trying.
73s.
- 399
73s.
- 399
OK Gang, this is interesting, I bought another 11.325mhz xtal and replaced the other and now the frequency is dead on on AM, USB, LSB. I was pretty sure that problem was the cryustal and it was. Now for the strange part, it receives but receive is BARELY audible. I am an excellent desolderer and re solderer and took out the old crystal and installed the new one, CAREFULLY, did not hit anything. Anyway, it is not the speaker or speaker jacksjacks, I tried 1 and 2 and phones, all the same. It is not the squelch or RF Gain. Can someone tell me what to try? Again, I am handy and not afraid to try. I will also make a separate post just for the audio problem. Thanks again for all who help. Adam
Hi all, I made the veteran mistake, I forgot it needs the mic to receive, it's fine. Ouch!! Thanks, Adam
do you have a crystal checker to measure the frequency of both your 11.325 crystals?
I would be very surprised if two crystals that were within specs made a 5khz difference.
even if one was 11.325 and another was 11.3258. even if you triple the 800hz difference, you only get 2.4Khz.
I have personally never seen a tripler crystal for this chassis be that far off from design specs, unless it was just plain defective and didn't work at all.
what am i missing here?
LC
I would be very surprised if two crystals that were within specs made a 5khz difference.
even if one was 11.325 and another was 11.3258. even if you triple the 800hz difference, you only get 2.4Khz.
I have personally never seen a tripler crystal for this chassis be that far off from design specs, unless it was just plain defective and didn't work at all.
what am i missing here?
LC
- No one is chatting at the moment.
...runna pile-up on 6m SSB