How To Fix a Cobra 29 CB Radio That Keeps Blowing The Fuse

[@tomluque]

I have worked in electronics repair for 50 years. This method is a type of protection circuit called a "Crowbar". To stop equipment dead in its tracks to prevent harm or death to a person or equipment. But it seems to me if you just want to prevent the problem of accidental reverse polarity hook-ups, place a diode in series with the fuse line to block current flow if hooked up backward by mistake. The downside is the diode's forward voltage drop, which may be 0.7 volts to 1.2 volts that you lose going to the CB. For example, The alternator puts out 14 volts, minus a 1-volt drop across the diode, which means that the voltage to the CB is 13 volts. You need to know what the minimum voltage is required for the CB to transmit on the maximum setting.

[@Roger70742]

I had the very same problem curate it myself thank you for the video it assured me.

[@NoNonsenseKnowHow]

No problem at all man. Thanks for dropping a comment

[@cajuncoinhunter]

I seen you not long ago in a live stream that I was in the panel and I rhink we were talking small engines or tools...... Yep you did the repair the right way...

[@tony6796]

I just purchased a cobra and I connected everything properly but it turns on and off within a matter of seconds and the fuse still looks good.

[@jonathanfauver7395]

Thanks a million for this video! I clipped mine and it fired back up! Now to fix on a few other things

[@kwinterburn]

The 1N4004 is a 1 amp 400v diode it blew because it was overcurrented its supposed to short if it was a 3 or 5 amp it would have survived most any diode would work in this application 1N4001 is 50v and would be fine

[@NoNonsenseKnowHow]

Awesome. I appreciate the detailed information. Thanks!

[@warzone7571]

Hello sir i have a tyt th-9800 and i have to replace the diode i dont know witch diode too use my question is can i use any diode.????

[@Guysm1l3y]

I wonder if with that plug if those are both intended as "source" cables? Like they're wired up so the output is the connector, where one has the "source" being a cigarette lighter and the other the "source" is the bare red/black wires. When you hook the connectors to each other it effectively flips the polarity (since those plugs are 1-way) making the red wire negative if the cigarette lighter plug is the source.

[@NoNonsenseKnowHow]

Yeah it must be something like that. I just grabbed them both separately out of a big box of wires I had. My fault for not checking. Hopefully won't make that mistake again in the future.

[@Zbo59]

Just went through this today, I spent a crap ton of time attempting to fix it, but ran out of time and will go down to the yard tomorrow and snip the diode. I made the mistake of reversing the polarity when I spliced the wires. My question is, if I do not reverse the polarity again, will my Cobra run well without replacing the diode?

[@NoNonsenseKnowHow]

it should work if the diode acted properly. if you snip it and you leave it that way though if you ever reverse it again you will probably fry it

[@clarencewiles963]

Thumbs up 👍 not every cord is as you think ✅

[@seandrake7534]

Ok I my radio is from the 90s sometime and it has been in storage since 2002 unfortunately there has been mice and only who knows what doing only who knows what on it Any way I had it hooked up and working and I unplugged it but when I plugged it back in somehow I got it plugged in backwards anyway thanks for the video but do you know if it would be ok if I sprayed the board down with contact cleaner it's pretty dirty and a lot of dust on it

[@SiCkDiAbLo]

So when you cut the diode, radio worked??

[@NoNonsenseKnowHow]

Yea

[@jessesalcido2562]

Sweet thanks !!

[@hunterrosier4426]

When your diode blow did it start to smoke?

[@NoNonsenseKnowHow]

No

[@hunterrosier4426]

@@NoNonsenseKnowHow ah. My 29ltd must be fkd then 😬

[@NoNonsenseKnowHow]

Yeah that's what it sounds like. More likely than if it was to just blow real quick

[@hunterrosier4426]

@@NoNonsenseKnowHow well thanks for the help. Ebay here I come lol

[@cajuncoinhunter]

@@hunterrosier4426 If your radio was hooked up backwards 2 things could happen , the diode blows in his case it shorted , that why when the diode was cut the radio worked , or the diode opens when a bigger fuse is put in and a trace gets burnt ..... Then a new trace has to be made .... I have repaired quite a few thousand in my radio shop .....

[@sheldonwhite1010]

What Diode does it take

[@NoNonsenseKnowHow]

I don't remember off hand. I thought that I mentioned it in the video but I could be mistaken?

[@josephbednarsky]

What is the replacement diode?

[@NoNonsenseKnowHow]

I forget exactly which one it was but if you just get a diode variety kit, it should have the right one. Or just replace yours with whatever one is currently in there

[@josephbednarsky]

I used a 1N4004.

[@NoNonsenseKnowHow]

Yeah that sounds about right. What came out of it?

[@josephbednarsky]

There was nothing left to the one they came out that's why I asked.

[@cajuncoinhunter]

Any 1n4001 thru 1n4006 will work...

[@richardbates2367]

I have almost the exact same cb I think since 2001

[@evertonstay1135]

The diode is bad ,its accross the power wire in the radio

[@eddienation118422]

So if I cut that’s dial it will still work ?