hello friends on this forum, I have a problem with the motorola cm450 cb and I see it's the same as the 555 can't rx and tx, the radio turns on only the noise freq is empty, I'm looking for the schematic but haven't found it, I hope my colleagues here can help solve this problem..thanks in advance..
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Motorola CM540 no rx
- Thread starter putra
- Start date
Hi, and welcome to the forum.
This kind of problem is a lot like telling a mechanic "my car won't start". He'll start with questions about what does appear to work. Do the dashboard lights come on when you turn the key to the first click? Do the lights dim a little when you turn the key farther? Do you hear a "click", or does it just go "ruh, ruh, ruh" and won't catch.
First thing I would want to know is how many people have tried to fix it since it first broke down? Clearly they did not succeed. For every attempt at repair that fails I have learned to expect at least one new fault added to the original one the prompted taking the covers off.
Troubleshooting is a methodical process of identifying which parts of the radio aren't broke. The mechanic will check to see that the motor is getting fuel and a proper spart pulse first. This radio is almost 45 years old. Don't assume that it has only one fault, even if nobody has had their hand in it since it failed. 45 years can be an awkward age for a radio. The mileage will have a lot to do with what's gone bad. Just one problem, there is no odometer to read the miles from.
A low-mileage radio usually has fewer faults.
Just what tools do you have? Like getting your car to start, you'll need the right tools. At a minimum, a dummy load, wattmeter, general-purpose multimeter and soldering/desoldering setup. A frequency counter to see what frequency is coming out of the radio when it transmits is nice, but only necessary if the radio has a problem with that.
IIRC, this radio's circuit board has foil traces on both top and bottom surfaces. There will be metal sleeves that join the foil pad on one side to the pad on the opposite side of each hole. This can lead to puzzling issues if that sleeve accidentally gets pulled out of a hole while removing a component.
It was a higher-tech CB when it was made, but that really was a long, long time ago.
I can't find service data online. I'll check to see if I have any at work when I get there tomorrow. Probably not, but it's worth a look.
73
This kind of problem is a lot like telling a mechanic "my car won't start". He'll start with questions about what does appear to work. Do the dashboard lights come on when you turn the key to the first click? Do the lights dim a little when you turn the key farther? Do you hear a "click", or does it just go "ruh, ruh, ruh" and won't catch.
First thing I would want to know is how many people have tried to fix it since it first broke down? Clearly they did not succeed. For every attempt at repair that fails I have learned to expect at least one new fault added to the original one the prompted taking the covers off.
Troubleshooting is a methodical process of identifying which parts of the radio aren't broke. The mechanic will check to see that the motor is getting fuel and a proper spart pulse first. This radio is almost 45 years old. Don't assume that it has only one fault, even if nobody has had their hand in it since it failed. 45 years can be an awkward age for a radio. The mileage will have a lot to do with what's gone bad. Just one problem, there is no odometer to read the miles from.
A low-mileage radio usually has fewer faults.
Just what tools do you have? Like getting your car to start, you'll need the right tools. At a minimum, a dummy load, wattmeter, general-purpose multimeter and soldering/desoldering setup. A frequency counter to see what frequency is coming out of the radio when it transmits is nice, but only necessary if the radio has a problem with that.
IIRC, this radio's circuit board has foil traces on both top and bottom surfaces. There will be metal sleeves that join the foil pad on one side to the pad on the opposite side of each hole. This can lead to puzzling issues if that sleeve accidentally gets pulled out of a hole while removing a component.
It was a higher-tech CB when it was made, but that really was a long, long time ago.
I can't find service data online. I'll check to see if I have any at work when I get there tomorrow. Probably not, but it's worth a look.
73
thank you for your willingness to reply to my post, sorry if maybe my way of speaking is not pleasing, because I'm still learning the language
English, as you said, it's true that the PCB has a top and bottom line, or double layer, previously I've done a temporary check with the equipment I have without freq counter i found the PLL oscillator section that doesn't work, previously I thought the cause was that the voltage for the PLL IC was TC9105 and TA7310
which doesn't exist, and I found a broken transistor and have replaced it with the same type number and the voltage is there and still can't receive only big noise is there. it's a bit difficult to check the next component because the motorola cm 450 pll is protected by cans and wax parts of the top on the pll, at least it needs a schematic for further checking in this section, but at least it still really needs guidance and input based on existing experience by colleagues in the forum here, thank you very much in advance.
English, as you said, it's true that the PCB has a top and bottom line, or double layer, previously I've done a temporary check with the equipment I have without freq counter i found the PLL oscillator section that doesn't work, previously I thought the cause was that the voltage for the PLL IC was TC9105 and TA7310
which doesn't exist, and I found a broken transistor and have replaced it with the same type number and the voltage is there and still can't receive only big noise is there. it's a bit difficult to check the next component because the motorola cm 450 pll is protected by cans and wax parts of the top on the pll, at least it needs a schematic for further checking in this section, but at least it still really needs guidance and input based on existing experience by colleagues in the forum here, thank you very much in advance.
yes, thank you sir for the instructions, I have checked some of the videos, and as a first step as I have done, but finally returned to the schematic which is very difficult to find plus important components such as the ic pll tc 9105 are no longer on the market in my country.
Hello Putra. I am just clarifying.... your title line says CM540. Your description says CM 450. I also saw when you were asking about getting the schematic that you said CM 450 there as well.
Is the radio you have actually CM450 or CM 540?
I do show a SAMS for a CM540 in CB-233.
I am going to try to send the CM540 just in case that is the correct radio!
Please take a look.
Is the radio you have actually CM450 or CM 540?
I do show a SAMS for a CM540 in CB-233.
I am going to try to send the CM540 just in case that is the correct radio!
Please take a look.
I'm very sorry for my mistake, sir, the correct one is 550, I focus on the language because I'm still learning English, thank you very much for the files that you have uploaded here, hopefully it will be a blessing and there are other colleagues who need it
thank you sir, that's why I apologize in advance if there are words that are difficult to understand and the sentences are reversed☺
Putra,
I do hope that you notice that my second upload was the CM550 and CM555. They are both in the one volume.
I hope that it helps you!
Hello Guitar_199, could you kindly re-scan just the circuit schematic diagram please, as I cannot read many of the values of the CM550 components.
Many thanks, thank you.
I am out of town and won't be able to until I get back home. We have a family medical situation on our hands an that may not be until the weekend. I hope you can understand....
Ok thank you, there is no urgency, whenever you can, my best wishes for your family.
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