Help with MA COM M7100ip - "intermittent / no transmit"

[ckriss]

Hi. I have no background in radio so please forgive my lack of radio terminology or radio knowledge. My main background is automotive. I have some experience repairing circuit boards down to the electrical components.

I work on fleet vehicles and have been given the task of repairing our radios. Some of our M7100ips are transmitting intermittently. When looking at the TX light on the faceplate of the radio while pressing and holding the push-to-talk button, the TX light blinks about 4 times within 2 seconds and then goes out. All the while, nothing is transmitting. When replacing these bad radios with a known working one, the TX light may blink a couple of times but eventually stays on and transmits fine.

Is there a known fix for the radios that only flicker for a short while and also does not transmit? Thanks

This is what the radio looks like
https://www.picclickimg.com/d/w1600...is-M-A-COM-M7100ip-800mhz-Great-condition.jpg

 

[radioman2001]

I am going to assume these are trunking radios as you say the radio blinks a few times and then transmits. If this is so the non functional radios could have the following, 1 they are not authrorized to work on the system or have been turned off, 2 they have bad receivers or bad antenna, and 3 bad transmitter. You need to switch the radio to a conventional non trunking channel and then check the power out. Beyond that they need to sent to a repair facilitiy that can actually test the radio.

 

[rescue161]

The TCXO is more than likely off frequency. This can be checked with a service monitor and the Maintenance utility that comes with the programming software. You'd check the frequency and adjust the AFC until it is within a few Hz of the test frequency. If they truly are trunking radios, by changing them out, you should also update your database so the system admin knows what radio is in what vehicle. Otherwise, you can create a mess, especially if you are decommissioning a radio. The SA will need to remove that radio from the system.

 

[ckriss]

I am going to assume these are trunking radios as you say the radio blinks a few times and then transmits. If this is so the non functional radios could have the following, 1 they are not authrorized to work on the system or have been turned off, 2 they have bad receivers or bad antenna, and 3 bad transmitter. You need to switch the radio to a conventional non trunking channel and then check the power out. Beyond that they need to sent to a repair facilitiy that can actually test the radio.

Thanks for the reply
1) I dont believe they have been de-authorized or have been turned off.

2 and 3) I’m unsure how to test for those components if they are inside the radio unit. We do have a roof mounted antenna and everything works fine once the radio is replaced

 

[ckriss]

The TCXO is more than likely off frequency. This can be checked with a service monitor and the Maintenance utility that comes with the programming software. You'd check the frequency and adjust the AFC until it is within a few Hz of the test frequency. If they truly are trunking radios, by changing them out, you should also update your database so the system admin knows what radio is in what vehicle. Otherwise, you can create a mess, especially if you are decommissioning a radio. The SA will need to remove that radio from the system.

I had to look up what a TCXO is. I think you are correct. Since the radio transmits intermittently, the frequency may be off by just a tad bit.

The program we use is from Tyco Electronics / MA COM. It is called “ProGrammer”. I am unsure how to change the frequency or adjust the AFC. We do use ProGrammer to adjust volume and change the vehicle identification number when installing a new radio in a vehicle

I will look more into the program. Thank you

 

[rescue161]

It's called Maintenance and is part of the ProGrammer software package. But please don't change anything without first backing up the Tracking Data and second, make sure you you are verifying the transmit frequency using a calibrated service monitor.

 

[radioman2001]

It sounds like to me that 1 you don't have the test equipment to properly align the radio and 2 you are not a licensed radio tech. If this is so save yourself a lot of grief and possibly heavy fines from the FCC and take the bad radios to licensed radio repair facility.

 

[rescue161]

If you find that you can still receive fine with the problem radios, then it is almost certain that the TCXO is out of alignment.

 

[ckriss]

It sounds like to me that 1 you don't have the test equipment to properly align the radio and 2 you are not a licensed radio tech. If this is so save yourself a lot of grief and possibly heavy fines from the FCC and take the bad radios to licensed radio repair facility.

You are correct

 

[ckriss]

If you find that you can still receive fine with the problem radios, then it is almost certain that the TCXO is out of alignment.

Yes we can receive just fine on the problem radios. Is the TCXO something that can be replaced and will work right out of the box? Or will a replacement TCXO still have to be adjusted? If so, it may be cheaper for us to just remove and replace the TCXO instead of getting the correct test equipment to try to adjust frequencies. I do have experience with circuit board repair.

 

[rescue161]

No. It is adjustable with the maintenance software. You connect the radio to a service monitor and key up on a test freq, we'll say 851.0625. Then you look on the service monitor and it should show 851.0625. What you'll find is that the service monitor will probably show something like 851.2500. You then open up the software and reduce the AFC. Well pretend that it is 125, so you'll bring it down to 120 and key the radio again. If it is on freq at that point, you'd save that setting and then the radio would probably work on the system correctly.

 

[rescue161]

Do you not have a radio shop that maintains your fleet? I would think they would be on a maintenance schedule to ensure that they are working correctly.