Ok. The radio receives fine.......AFTER...I key the mic. And that's only majority of the time. There are times that it won't come back after I key up. I have changed TR35 and D43 thinking it was the switching trans. I am thinking it's the AGC because when the RX is out, it's not out completely. It's extremely muffled. Very strong signals come through but they too are very muffled. Because of that theory, I changed TR10, D5 thru D10. Any ideas?
-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
Cobra 148 RX problem
- Thread starter jetman
- Start date
Agree with Sonoma.
If that doesn't pan out, then take another path.
If a 10v cap has decided to go belly up; then change out all of the 10v caps. Don't wait for the next one to dry up and quit on you. Change all 10v caps out to 16v or 25v with the same capacitance value. There are 10-12 caps that are 10v - IIRC. If this is an older 5 pin/side mic plug radio; they are long overdue to failure anyway. Been there/done that several times. If you doubt that, take a few out and test them to see for yourself.
Not saying that is the problem you have; but it could be.
Dried out old caps in older Cobra/Uniden radios are commonplace.
If that doesn't pan out, then take another path.
If a 10v cap has decided to go belly up; then change out all of the 10v caps. Don't wait for the next one to dry up and quit on you. Change all 10v caps out to 16v or 25v with the same capacitance value. There are 10-12 caps that are 10v - IIRC. If this is an older 5 pin/side mic plug radio; they are long overdue to failure anyway. Been there/done that several times. If you doubt that, take a few out and test them to see for yourself.
Not saying that is the problem you have; but it could be.
Dried out old caps in older Cobra/Uniden radios are commonplace.
Last edited:
they do not function like the electro caps. I normally just have one quit or it degrads gradually and does not work intermitantly as electro do. at least that is my experiance with them. the hit and miss sounds more like a cold solder joint to me, at least that is what I would look for 1st.
jetman, i didnt see in here where you tried a different mic yet.
have you?
i would assume that you have, but if not; definitely try it because a bad mic switch will cause exactly the problems you are describing.
if its not that, have you done any channel mods to the radio or messed with the VCO at all?
LC
have you?
i would assume that you have, but if not; definitely try it because a bad mic switch will cause exactly the problems you are describing.
if its not that, have you done any channel mods to the radio or messed with the VCO at all?
LC
Yes, I have tried a different mic. I have also checked the volts on VCO. All seems to be fine. There is an old echo board but no other mods. I have gone over the echo and all looks good except it was a truck stop mod. A-hole just allowed the board to sit in there freestyle like. who knows the damage it has caused. I'm in the process of replacing all elect. caps. We will see where it gets me. I'll keep everyone informed.
Good luck with that thing, had one that had been hacked up and had an echo board and channel expo kit added. It stopped working and ended up being a non fixable radio for the cost I had in it. It had been so hacked up inside I was at awe when I popped the kids I couldn't believe it worked as long as it did!! Hope you get it working. Wish I had mine still and it worked. It was an older side mic that was a great radio, but some dip shit thought adding a truck stop echo board and a channel kit, wish I had photos, like you the echo board and the expo components were just laying in the radio wrapped in electrical tape. Boy did it look UGLY!!! but anyway good luck with getting that radio going, they are great ssb radios when not been modded and crap added.
jetman, if you've already isolated the problem to inside the radio, make sure you look at the RX/TX light as your keying and unkeying the mic.
if that light turns from green to red every time you key the mic, regardless of the state of the receive problem; then you can pretty much eliminate the keying circuit as the problem area.
at this point im with the other guys in suspecting an intermittent electrolytic capacitor, and you might be on to something in thinking about the AGC circuit.
be sure to check C23, as it determines the "decay" time of the AGC circuit and if bad, could cause a problem like this. (also check C24 and C25)
LC
if that light turns from green to red every time you key the mic, regardless of the state of the receive problem; then you can pretty much eliminate the keying circuit as the problem area.
at this point im with the other guys in suspecting an intermittent electrolytic capacitor, and you might be on to something in thinking about the AGC circuit.
be sure to check C23, as it determines the "decay" time of the AGC circuit and if bad, could cause a problem like this. (also check C24 and C25)
LC
If this was my radio, I would have shot it by now! :bdh: I did finally fix the problem. I could not isolate the actual faulty component, but was able to isolate the are. When I pressed the the board, the RX would come alive. It seemed to be extra touchy in the IF area. So I broke down and cried for a few minutes and then decided that it was impossible to get thru all of that was on the board, so I flipped it over and reheated ALL of the circuit joints and it worked, but since my soldering iron is not well grounded, I did not have power on the radio to know which guy was the culprit. oh well. she is fixed. Thanks for all the help crew!!!! 
We will see y'alll next time!!!
We will see y'alll next time!!!Break down and get on eBay! See one that's for parts for $32 right now. Can't tell you how many I have bought "broke" that just needed a fuse, cleaned mic gain knob, or just resolder the antenna wire to the pcb and paid more for shipping than the radio.
Sent from my iPhone using Tapatalk
- No one is chatting at the moment.
-
-
dxBot:63Sprint has left the room.
-
dxBot:kennyjames 0151 has left the room.
-
-