Any tips to prevent hooking CB up backwards

[Chainsawgang]

Hello TECHS,
I have an easy one for you guys, What is a good way to prevent hooking my CB/ 10 meter up backwards! (Besides just making sure red to red etc.) I slipseat & sometimes I come to work brain-dead on a Monday AM . Not to mention sometimes the leads could be mis- marked any ideas ??

 

[ken white]

Hello TECHS,
I have an easy one for you guys, What is a good way to prevent hooking my CB/ 10 meter up backwards! (Besides just making sure red to red etc.) I slipseat & sometimes I come to work brain-dead on a Monday AM . Not to mention sometimes the leads could be mis- marked any ideas ??

Replace the connectors with a polarized plug or use different individual connectors for the (+) and (-) connections...

 

[Hamin' X]

Use a full wave bridge rectifier. There will be some voltage drop, but it will still work.

Rich

 

[Chainsawgang]

A buddy of mine said you can put a fuse on the ground side of your power cord. Because he said," It doesn't hurt the radio to ground your + or positive wire the problem is...when you power up the - or ground side" . I guess that makes sense. When the power goes in the ground side of the radio it blows (hopefully ) the diode. If I put a fuse on the ground side what size fuse would you use like for a Connex 3300 HP ? And will this work ?

 

[Beetle]

Nothing works better than knowing what you're doing and why.

 

[Chainsawgang]

Nothing works better than knowing what you're doing and why.

WELL SAID BEETLE !

 

[Geekster]

Hello TECHS,
I have an easy one for you guys, What is a good way to prevent hooking my CB/ 10 meter up backwards! (Besides just making sure red to red etc.) I slipseat & sometimes I come to work brain-dead on a Monday AM . Not to mention sometimes the leads could be mis- marked any ideas ??

Replace the connectors with a polarized plug or use different individual connectors for the (+) and (-) connections...

I concur this may be the best and easiest solution for your application.

 

[Captain Kilowatt]

HERE is one way without a voltage drop.

 

[Hamin' X]

HERE is one way without a voltage drop.

Sweet.

Rich

 

[DTB Radio]

I used that circuit once a loooong time ago. I had completely forgotten about it because I so rarely see that problem anymore.

 

[Chainsawgang]

Hey DTB, Does the fuse in the ground side of your power cord work very well ?

 

[ken white]

Hey DTB, Does the fuse in the ground side of your power cord work very well ?

Since current needs a complete path to flow, the fuse can be in either the (+) or (-) power leads because both wires will see the exact same current, unless there is a ground fault.

However, putting the fuse in the (-) line will not protect the equipment from reverse polarity any better than having the fuse in the (+) line.

 

[Captain Kilowatt]

Usually when someone smokes the protection diode it is when they hooked up the wires backwards and did not use a fuse.I ALWAYS use a fuse in the B+ line and now with the newer ham gear the B- as well.The big reason for having a fuse in the neg lead is if the main ground from the battery to the vehicle's chassis fails then all the ground is flowing through your radio's neg lead and that includes the starter. :shock:

 

[ken white]

Is'nt the the purpose of the large diode at the power input section of most cb radios>?

I have repaired several rigs that got connected back to front and some where the guy plugged the radio back in the right way and left it there .

This one guy said when he hooked his galaxy up wrong that smoke started to come out of the radio and when he hooked it back up right it really smoked.lol that's the only one I had to repair a trace on the ciruit board and replace the protection diode.

karo, the diode will be forward biased when the power leads are reversed, and since the diode is located across the power lines with no current limiting, the fuse will blow whether it is located in the positive lead or negative lead - it doesn't matter.

Usually when someone smokes the protection diode it is when they hooked up the wires backwards and did not use a fuse.I ALWAYS use a fuse in the B+ line and now with the newer ham gear the B- as well.The big reason for having a fuse in the neg lead is if the main ground from the battery to the vehicle's chassis fails then all the ground is flowing through your radio's neg lead and that includes the starter. :shock:

QRN, the entire vehicle electrical system has a main (single point) ground connection located on the engine block. Should the engine, battery, and vehicle body loose this single point connection, the electronics and electrical system would all be floating at different values and nothing would work as a system.

Also, since the starter is grounded to the engine block when it is bolted up, there is no way the starter current will flow through the CB's negative lead. This starter current flowing through the CB (-) connection is an internet myth...

You can fuse the negative lead if it makes you feel good, but it is not a good idea unless the positive is fused too.

The reason the positive lead is fused is to remove power from the device when there is an overload condition. If the negative lead is the only lead fused, then power will still be applied to the device when the fuse blows. This means that unless the chassis/device is floating, current will flow back to the source through whatever ground path it can find, so a fire in the wiring could still occur when over loaded.

 

[ken white]

I lost engine ground on an old chevy and the head lights would blow when I turned them on so I suppose the engine's electrical was searching for ground and it found it through the light circuit.

Maybe, but I doubt it.

It is more likely the lights saw a voltage that was greater than what they were designed for. When discreet power/ground paths exist within numerous connected systems, the voltages seen at various connection points can be smaller than ideal, close to ideal, or greater than ideal in magnitude. This is not a good thing since things might not work, best case, or will be damaged, worse case. By having a single point ground, every voltage and signal is referenced to the same point and all port voltages are now at the levels they were designed for.