A neighbor came buy wanting me to look at his CB, just says it doesn't work right. Well I got around to opening it up to see if anything was out of place, everything "looked" ok. I hooked it up to a PS, wattmeter and dummy load. Turned it on and it blew the fuse in the power cord. Replaced fuse and did it again, power cord is hooked correctly, any ideas ?
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Problem with Uniden Grant
- Thread starter park
- Start date
your neighbor hooked it up backward black to positive red to negative (REVERSED POLARITY) protection diode is blown look where the power and ground come into the radio and atatch to the board at back of radio you will see the little bugger there. 
Yeah if he's lucky that's as far as it went, IN4003 is the value of the diode in question, you can get it at ratshak and replace then plug her in again and see if it sings.your neighbor hooked it up backward black to positive red to negative (REVERSED POLARITY) protection diode is blown look where the power and ground come into the radio and atatch to the board at back of radio you will see the little bugger there.
Good point and as you said it all depends on how far it got Ive seen easy fix and Ive seen nightmares traces lifted off the foil side of the board looking like a roller coaster at an amusement park.
He should be able for the most part to eyeball it although Ive seen them where they didnt look burnt or bad but indeed tested bad and when I went to pull them out they crumbled or fell apart. He just needs to look at it good and make sure I believe these rectifier diodes come in packs of 2 at radio shack so thats 2 chances. I bought 100 of those last time I bought them or odered them because for awhile it was a common thing with truck drivers where a good friend of mine works.
He should be able for the most part to eyeball it although Ive seen them where they didnt look burnt or bad but indeed tested bad and when I went to pull them out they crumbled or fell apart. He just needs to look at it good and make sure I believe these rectifier diodes come in packs of 2 at radio shack so thats 2 chances. I bought 100 of those last time I bought them or odered them because for awhile it was a common thing with truck drivers where a good friend of mine works.
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best to de-solder one end and do a continuity test to make sure but I would start with the one on the power input, eliminate it first then move on to the one on the board.
The one on the input is most likely a IN5404 rated at 3 amps and has the ratshack cat#276-1144 and comes on a card of 2
And I did not know this until today I read that you should not use clipper style nippers to trim leads on diodes, they say to use scissor style cutters to avoid damaging the diode due to the shock caused when the lead is snipped.
The one on the input is most likely a IN5404 rated at 3 amps and has the ratshack cat#276-1144 and comes on a card of 2
And I did not know this until today I read that you should not use clipper style nippers to trim leads on diodes, they say to use scissor style cutters to avoid damaging the diode due to the shock caused when the lead is snipped.
does the grant have a diode on the power connector?
i thought there was only the one on the PC board.
park, it may be the reverse polarity diode, which is the most likely cause, but it could also be a shorted final or driver transistor. so if you replace the diode and it still blows fuses, unsolder the leads of the final and driver and do the diode test on them with your DMM.
mack, i have heard the same thing about clipping diodes, but i heard that it only applies to shottky type diodes.
we should look into this a bit more and get the facts!
in a new thread of course! LOL
LC
i thought there was only the one on the PC board.
park, it may be the reverse polarity diode, which is the most likely cause, but it could also be a shorted final or driver transistor. so if you replace the diode and it still blows fuses, unsolder the leads of the final and driver and do the diode test on them with your DMM.
mack, i have heard the same thing about clipping diodes, but i heard that it only applies to shottky type diodes.
we should look into this a bit more and get the facts!
in a new thread of course! LOL
LC
Hey thanks guys, haven’t had a chance to get on the PC till now. I think I'll give it back to him and let him know it's over my head, hopefully he won't blame it on me !
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