Hello all , this afternoon I attempted to plug the power cord into my old orange screen RCI 2950 and blew the fuse, I must have had the cord reversed. So now of coarse it blows the the fuse immediately even when the cord is plugged in correctly and the radio is in the off position. Any ideas on what needs to be replaced? thanks guys
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Shorted 2950
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Sure.
Don't recall which diode is the protection diode - ATM. But you can find it no problem. Find the schematic for this radio on CBTricks.com. Start at the point where the power plug enters the radio. The first diode closest to the power plug will be the protection diode. Replace it with a 1N4003 - or whatever number is on it. Don't recall if it uses a 1N4003; might not. Most other radios do.
EDIT:
Yep.
D105; and it is a 1N4003
http://www.cbtricks.com/radios/rci/rci_2950/graphics/rci_2950_sch.pdf
Don't recall which diode is the protection diode - ATM. But you can find it no problem. Find the schematic for this radio on CBTricks.com. Start at the point where the power plug enters the radio. The first diode closest to the power plug will be the protection diode. Replace it with a 1N4003 - or whatever number is on it. Don't recall if it uses a 1N4003; might not. Most other radios do.
EDIT:
Yep.
D105; and it is a 1N4003
http://www.cbtricks.com/radios/rci/rci_2950/graphics/rci_2950_sch.pdf
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Yes absolutely you popped the rectifier diode and this is crazy because years ago I had done the same thing with a Mirage 2950EX and was puzzled because of how the 3 pin plugs are made to only plug in one way.
It was a mobile I had diconnected and remounted in my wifes vehicle and I had reached behind the radio and tried blindly plugging it in and smelt it instantly and new what happend. I repair these mishaps with the diodes people do all the time but it usually is because the power leads are reversed and reverse polarity is a no no with DC powered equipment and this is where the rectifier (protection ) diode does its job.
To this day Im still puzzled how that plug made contact on me but it wont ever happen again to me thats forsure because I reach back and feel the pins to make sure even though I am aware of the normal direction the pins are layed out but you never know so better safe then sorry.
That diode is located right below the power socket connection on the radio you will certainly see it just be sure to look at the direction of the diode the printed arrow with the line on the circuitboard is where the silver banding or line on the diode lines up with that is its direction.
It was a mobile I had diconnected and remounted in my wifes vehicle and I had reached behind the radio and tried blindly plugging it in and smelt it instantly and new what happend. I repair these mishaps with the diodes people do all the time but it usually is because the power leads are reversed and reverse polarity is a no no with DC powered equipment and this is where the rectifier (protection ) diode does its job.
To this day Im still puzzled how that plug made contact on me but it wont ever happen again to me thats forsure because I reach back and feel the pins to make sure even though I am aware of the normal direction the pins are layed out but you never know so better safe then sorry.
That diode is located right below the power socket connection on the radio you will certainly see it just be sure to look at the direction of the diode the printed arrow with the line on the circuitboard is where the silver banding or line on the diode lines up with that is its direction.
What are you guys using for fuses if you are blowing the protection diodes? I have made a mistake or to as well when crossing the polarity and have always blown the inline fuses but never the diodes. The whole idea is that the diode conducts when the polarity is reversed and that causes the fuse to blow. As soon as the proper polarity is applied it should work fine.
The protection diode will blow every time someone puts the '-' power wire on the '+' battery/power supply post; and vice-versa. CB radios don't have a fuse on both the positive and negative wires like most Ham radios do; just the positive power wire. I've fixed a bunch of radios for locals that make this mistake. Either that, or they jam the power connector in the wrong way into the back of the radio like TonyV pointed out. I buy a 20 piece bag of 1N4003's @$.05 ea every once in a while.
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I disagree Robb. It only takes one fuse inline, in fact the two times I made that mistake was with a power cord that only had one fuse in the + line. One radio was a CB and the other was a 2m rig. I actually heard one fuse go POP! and thought Oh shit! The two fuses inline are for other reasons involving loss of a ground wire from the battery to the chassis and preventing starter current from traveling through the radio's ground lead.
OK I just looked up the specs for the 1N4003 and see the problem. Cheap assed manufactures are using 1 amp diodes now.
That's the problem The 1 amp diode blows instead of or along with the 5 amp fuse or whatever the fuse is. I guess gone are the days of the big assed 6 or 10 amp diodes in the DC input. Shame really. There is no need of using a tiny little 1 amp diode when for about $0.01 more they could use a REAL protection diode like they used too. Those old 6 or 10 amp diodes would take a surge of about 100 amps for a few milliseconds which was long enough to take out the fuse and survive. Yeah, some of us are old enough and experienced enough to remember those good old days when manufacturers did it right. The first time.Ok I just got back to this post and was about to explain to C.K. what the problem is but se he found it on his own and in a way I agree with the use of these rediculously small amp diodes. But in away for some its a good thing because Ive worked on radios where someone had a 10 15 and 20 AMP FUSE INLINE!!! The funniest and craziest thing Ive ever seen was ......Your gonna love this........ALUMINUM FOIL WRAPPED AROUND A BLOWN FUSE TO COMPLETE THE CURCUIT BECAUSE THE DUMB@$$ DIDNT HAVE A FUSE ON HAND BECAUSE IT KEPT BLOWING THE FUSES!!!! *Don`t do it*
*Don`t do it*
I don't have any problem with the $.05 diode blowing. Just so long as it does it real fast and not take any other fragile part in a radio out when exposed to a reversed voltage. Like a $5-10 voltage regulator (like a Cobra/Uniden MB3756 regulator) that might not be that easy to find and replace. The problem is, is that popping a diode is too easy to happen and not enough CB operators know how to fix it. They can probably still get the 1N4003 at their local Radio Shack - if there is one around. Might cost about $3 for a 3-pack or whatever; but the leftovers can be used in the future too. All they need to do is look up the schematic for their radio, know where to look, pay attention to the polarity of the diode they are replacing, and put a little quality soldering time in - done!
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My beef is that a component should never be selected so it is intended to be destroyed in the event of a simply human error. Most operators would have no idea what was wrong. Usually the diodes go short but I have seen a couple go open, literally blown apart inside. Guess what happens then.The guy replaces the fuse and promptly ruins his radio because he now has full reverse polarity. A larger diode would in all likelihood not have done that.
The funniest and craziest thing Ive ever seen was ......Your gonna love this........ALUMINUM FOIL WRAPPED AROUND A BLOWN FUSE TO COMPLETE THE CURCUIT BECAUSE THE DUMB@$$ DIDNT HAVE A FUSE ON HAND BECAUSE IT KEPT BLOWING THE FUSES!!!!
:laugh: XD XD XD!!!:headbang Another Ghettofied mod Via AC power:
Stack of penny's in the box on the house!
