okay ive got all my wiring done right and want to know why when i plug my cb in nothing happens i tested power inside and out i read somewhere it could be this little dilode but i dont know where its at but anyways can anyone help me with this
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Cobra 29 LTD no power
- Thread starter 1998f150wes
- Start date
Did you check the fuse in the power cord?
Do you have a multimeter to verify you have power at the end if the power cord?
Instruction video on how to identify and replace the protection diode is on my website.
Do you have a multimeter to verify you have power at the end if the power cord?
Instruction video on how to identify and replace the protection diode is on my website.
I think the schematic shows D23 is the protection diode. It is an 1N4003. If the radio keeps on poppin' fuses and won't turn on; that diode will need changing out.
A $.10 part - if that.
http://www.cbtricks.com/radios/cobra/29ltd_29ltd_st_29wx_st/graphics/cobra_29ltd_sm_sch.pdf
A $.10 part - if that.
http://www.cbtricks.com/radios/cobra/29ltd_29ltd_st_29wx_st/graphics/cobra_29ltd_sm_sch.pdf
Its a common diode. If there is a Radio Shack near you; they probably have it. There is a band/stripe on one end of this diode. The replacement diode has to be put in with that band turned/pointed the same way as the one you take out. It is near the power plug area of the radio.
If you look around you might be able to find an instruction video on how to change it.
PROTECTION DIODE HOW TO TROUBLESHOOT A RADIO THAT WONT POWER ON
According to the schematic, the fuse required is a 12v/2 amp.
Fuses are in any piece of electrical equipment to prevent fires.
Abide by it . . .
According to the schematic, the fuse required is a 12v/2 amp.
Fuses are in any piece of electrical equipment to prevent fires.
Abide by it . . .
Last edited:
i watched you video and my diode does not break apart what else would be the proplem if thats not it
So, I'm working on a 29 Ltd by that at first wasn't powering up. Diode 23 was bad, and I had to put a jumper from one pin to another to complete the circuit because the board got damaged.
The radio powers on and receives beautifully. However, when I key up, I have no audio. Solid 3 watt output on dead key, and close by receivers go quiet, but when I whistle or test audio, I get nothing in the receiver. No swing on the transmitting radio. Receiving radio just gets silent humm. Any input is appreciated.
The radio powers on and receives beautifully. However, when I key up, I have no audio. Solid 3 watt output on dead key, and close by receivers go quiet, but when I whistle or test audio, I get nothing in the receiver. No swing on the transmitting radio. Receiving radio just gets silent humm. Any input is appreciated.
Did you check the microphone? The wires inside its plug can often get broken.
Common.
I'd start there first.
Id put that diode back in the radio. They don't call it a protection diode for nothing. Not only does it protect the radio circuit from damage, but it also keeps it from going up in flames if you should leave it out and possibly hook the radio power up backwards again. Buy a few of these diodes and keep them around. Never know if the next radio someone might give you needs nothing more than a diode replacement.
Forgot how many radios people gave me because they didn't want to fix them; popped a new diode back in and gave it back. A 5 cent diode can put a smile back on a person's face - true.
Common.
I'd start there first.
Id put that diode back in the radio. They don't call it a protection diode for nothing. Not only does it protect the radio circuit from damage, but it also keeps it from going up in flames if you should leave it out and possibly hook the radio power up backwards again. Buy a few of these diodes and keep them around. Never know if the next radio someone might give you needs nothing more than a diode replacement.
Forgot how many radios people gave me because they didn't want to fix them; popped a new diode back in and gave it back. A 5 cent diode can put a smile back on a person's face - true.
Sorry, I forgot to mention that I did replace the diode. I also have quite a few back ups just in case.
Also, I did check the mike, it is in working order, thought maybe it could be the control for Mike gain, but I believe not. I'm actually working on two 29 Ltd's, ones a standard Ltd and ones a Bluetooth model. The Bluetooth model has no audio signal but broadcasts 3 watts, the standard Ltd doesn't broadcast at all. I'm working on them for my coworker, they were toasted by old coworkers that didn't know anything about cb's other than push the PTT button. I wanted to take a crack at them and have found this and other sources to be very helpful.
