Hi there, could you tell me how to hook up my old MCX1000 for power, i have the main box, the front module, the mic and the speaker. But i am not sure on how to hook it up so that at least the display will power up or more. It is to put in my show police car. Thank you verry much 1
Sure, the red lead goes to the battery pos and the black lead goes to the battery neg as some cb radios have a reverse polarity idiot diode fitted, go with caution. With a multi meter you can find the neg terminal using the continuity or the low ohms
select on the meter...1 meter lead goes to the metal body of the set and the other lead goes to one of the power leads WITH THE SET TURNED OFF when the meter responds to a contact and shows low ohm reading you have found the neg lead..this lead is directly connected to the fram/case of the set. With a few sets
you need to have the mike connected in order to power up. firstname.lastname@example.org
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you do not do it by resistance. To turn up the radio it is a variable resistor. What you do is connect a watt meter that can read PEAK or PEP watts AND AVERAGE or dead key watts.
First you check it on avg watts. Hook the radio up in line with the watt meter and set it on avg watts. key the radio. Stock is 4 watts. A lot of times when you peak a radio, you lower the dead key.(thats keying with no audio.) This allows you to get more modulation wattage, or swing wattage. If that has been done it will probably do 2 or 3 watts. If it has had the AM power raised in it, it could be more, this is no good. You want your dead key a bit lower.
Now check it on peak. Flip the meter to peak and make an AHHHHHHHHHHHHHHH noise into the radio. It should swing to anywhere between 15 and 20 watts.
You adjust the AMC while giving it audio and watching the meter on peak to adjust the modulation. 4 watts is legal modulation.
There are no knobs for AM power in the cobra 29 LTD. Soldering 2 parts inside the radio is needed to do this. If you are not comfortable with soldering inside of the radio, take it to a technician.If you feel you are up to it, here is how you to do it.
First make sure VR4 is all the way to the left. This will turn your modulation to full and will make your audio louder.
Next you will need a 220 uf 35 volt capacitor and a 1/2 watt 100 ohm resistor.
Now remove JP36. It is located right in front of the final transistor in the back right that is bolted to the heat sink.
put the capacitor in its place with the black tab facing the back of the radio.( this is most improtant because if you don't face it the right way you will blow your radio). Solder it in place.
Next on the trace side of the board, where all the solder joints are, solder the resistor to the spots where the cap was soldered. So the resistor is in between the 2 points of the capacitor.
Now your dead key will be at 2 watts. Now, you did say you wanted 1 watt. From my experience, 1 watt is not enough. you will under drive the box and blow the pills in it.
If in fact you do need only 1 watt, you have to play with what size resistor you put on it. if you increase the value of the resistor, you will get a lower dead key. If you lessen it, it will make the dead key higher. Get a multi pack of 1/2 watt resistors if your going to do this.
BUT** 2 watts should be what you need.
So you know. There are 2 types of wattage outputs in an AM radio. There is carrier signal or dead key, and then there is modulation or swing.
Your radio is going to do 2 watts of a carrier signal or dead key, and when you talk the meter will swing up when you talk if you have peak reading meter. it it only reads average, it will only show your dead key with only a swing of about 4-5 watts.
For low drive amplifiers, the dead key is usually all that needs to be set. The swing should be turned up (thats why you turn VR4 all the way to the left) witch will give you just over 20 watts swing. this will drive the box good. Any where between 20 and 35 watts will dive most boxes good.
COBRA RADIOS HAVE A DIODE THAT WILL BLOW IF HOOKED UP BACKWARDS, THIS IS A BLACK DIODE WITH A SILVER RING ON ONE END OF IT, YOU MAY HAVE TO TAKE IT TO A CB REPAIR SHOP AND HAVE IT REPLACED, HOPEFULLY YOU DID NOT USE OVER A 5 AMP FUSE
hi when you try to connect power to radio does it keep blowing fuses ,iff so remove the bottom panel/cover from the radio at the back of the radio where the power terminals enter the board you will see a black diode with a silver strip this is what we call a reversed or dummy diode remove this and your radio should work ok make sure to replace with new one you can find these in most cb radios goodlyck
Most modulation problem could be traced to: 1. mic or the cable and/or the mic connector; 2. AMC (amplitude modulation control) - it's a single transistor that regulates modulation and occasionally has been known to clamped on the mic audio; 3. the AM/SSB switch - spraying with contact cleaner is a temporary remedy; and/or 4. audio amp - however if your receive audio is good, then this does not apply.
Hope this be of initial help/idea. Without a model number, I can't be more specific as to component(s) or PCB location but pls post back for any developments (or lack thereof) or should you need additional information.
When the power was reversed this shorted out one of the components, possibly an Operational Amplifier. This tells me that there is no diode protection and possibly the circuitry is exposed directly to the input power supply. The fix would be to find the shorted component with the use of a schematic and a multimeter. Once you correct the shorted component then if possible you can add diode protection by putting a diode (forward biased direction) in the path of the positive line.
Again you will need a schematic, and a multimeter to work on this problem.