Tip & How-To about Radio Communications

How to build an Field Test meter

Get a big dial meter or decent size one out of radios or radio shack. place a diode on back (reverse polarity) of meter. The stripe side on (+) and the other side on (-) negative on meter. Ground one side and add Antenna to other ....When you Key up Cb radio nearby it will go up the scale. Add a Variable resistor or Volume knob and you will have a way to set selectivity(so as to not overdrive it).

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1 Answer

no noise static nothing


does it light up the front panel? If not did you accidently touch something that created an overload that may have caused the reverse polarity diode to blow?

Mar 01, 2014 | Radio Shack Powered ON TRC-444 40- Channel...

2 Answers

hooked my general lee up backwards heard a pop...what could it have been?


Hi looks like youve blown what we call the dummy diode at rear of radio this will have to be replaced although you can remove this yourself if you need it working pronto so firstly remove both covers of rig ,look closely at circuit board at the rear on the right hand side as you look you will see a black diode with silver stripe remove this ,your radio should operate fine now ,but please make sure you have it replaced as soon as possible as this protects your rig from damage goodluck

Oct 30, 2011 | Connex 3300 240-Channels Base CB Radio

1 Answer

what would cause my cb to blow fuses when u turn it on


d23 a 1n4004 diode second component from pa speaker port inside radio has failed. It is most likely that neg/pos polarity has been switched shorting this diode. It is there to protect your radio from reverse polarity as so it is names the "protection diode." 2 solutions first not recommended.

1. Cut the diode this will stop the directed grounding that is continuing to blow your fuse.
2. Go get a pack of 1n4004 and rosin core silver solder from radio shack and replace it paying attention to the direction it is installed.

just a side note the solder trace often burns in this area so a jumper wire soldered in around this bad area solder side maybe needed.

Jun 30, 2011 | Cobra 29 LTD CB Radio

2 Answers

I have a trc447cb radio, it kept blowing fuses, please help thanks...


This radio has been hooked up backwards. CB radios cannot be hooked up backwards or it will destroy it. However this is hope.

Because they can be damaged this way, there are polarity protection diodes in the radio that will blow if the radio is hooked up backwards, before it can hurt anything in the radio.

They are usually N1004 diodes. Is a big black diode that has a white stripe. And if it is blown, it will most likely be Black and burnt.

Open the radio, and look near the power section of the radio. It will be in the back near where the power cord plugs into it.

Look for a burnt black diode. That is the protection diode.

Get an N1004 or better from radio shack, and remove the burnt one, and put the new one in, making sure to put it in with the white strip on the same side as the original.

Once you have finished. Make sure the polarity is correct. Then hook up the radio, and turn it on. Should work fine.

If you want to validate that it is the correct diode, if you pull on leg out of the board, and turn on the radio, it will turn on. When the diode blows, it prevent the power from getting to the board, if you take it out, it will let it through. CAUTION. The radio will work again if you just remove the burn diode without replacing it. But if you hook it backwards again, it will be toast, and as good a door stop.

Sep 05, 2010 | Radio Shack TRC-447 CB Radio

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