CB Blowing Fuses???

[farmer]

I have a Radioshack TRC-521 (Cobra 19 knockoff) I've had it for awhile and its been in several vehicles and now it wont even turn on, it just blows fuses. I assume a have a short in the radio somewhere, how would I go about diagnosing it? I know it probably isn't fixable, but I'm cheap so I want to know haha
Is there supposed to be yellow crap on some of the innards?

 

[4x4junkie]

Is there supposed to be yellow crap on some of the innards?

Yes, it's to keep the parts from vibrating (which would cause their component leads to fatigue and break off).

When does it blow the fuse? Immediately when you connect power to it?

 

[farmer]

Yeah i hook power up and it blow the fuse

 

[4x4junkie]

Is it hooked up correctly? (positive to positive, neg to neg?). Did it get hooked up backwards accidentally at any point?

It sounds to me like a shorted polarity protection diode in the radio, which is an easy fix, but you gotta know which diode it is (usually it's near where the power leads come down to the circuit board).

 

[strvger]

just figure up what your time is worth on an hourly basis. figure how many hours you'll need to figure this problem out and fix it. multiply them and see if the total is more or less than the cost of a new or good used cb. simple enough, imho. oh, don't forget to add in the price of the replacement parts.

 

[farmer]

it may have been hooked up backwards... can you describe this diode? there one right near the leads, it looks like 2 is gray, and has gray gunk connecting the 2 "towers"
sorry I dont know the lingo... I have multimeters is there a way I can check the diode once identify it?

 

[feellnfroggy]

google it for images. I would either take it to a cb shop, which youll find near the highway by truck stops. or get a used one.

 

[4x4junkie]

A pic of a typical diode used for polarity protection in a radio (the black body is about 3/32" dia by about 1/4" long, and has a silver band at one end):

I'm not familiar with that particular radio, but I can say most likely the diode will be down around the power leads mounted stood up with one lead bent over, or it could be mounted down flat on the board in that same area.

Properly working, the diode should conduct in one direction, but show as an open circuit in the other. If it's shorted, its, well... shorted out of course lol.

Be sure to replace the diode even though the radio will work without it. If the radio should ever get hooked up backward again and there's no diode there, the destruction to the radio will be FAAAAAAAAAARRRRRR more extensive. (to the point the whole radio will be trash)

Edit:
I should probably add in:
Suitable diodes for replacements are: #1N4001, 1N4002, 1N4003 or 1N4004.
If you have a chronic problem of hooking radios up backwards (don't laugh or take offense, I've actually run into people like that lol), you could put a big fat 1N5401 thru 1N5408 diode in there. Just be sure there's a fuse there, as something else besides that diode would have to give otherwise.

Hope that helps