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Need Com 120A help .....

This forum exists for the purposes for discussing service monitors (This includes but is not limited to Motorola, HP, Aeroflex, GD, etc). Additional topics allowed include test procedures, interpretation of test results, where to find information about specific tests, antenna VSWR, return loss testing, duplexer and filter alignment, etc.

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Darel
New User
Posts: 8
Joined: Tue Jan 03, 2017 7:19 pm

Need Com 120A help .....

Postby Darel » Tue Jan 03, 2017 7:28 pm

Hello all ...

I was recently given a IFR Com 120A that seems to be in very nice shape but the power button up front will not turn the unit on or off ( I need to use the rear switch ). Also, after the self test it gives the message "rf term overheat, reduce rf input" although I have no rf going into it. If I hold the front power button down while I turn on the unit from the rear I can get it going and it seems to work ok but if the front power button is pressed it will freeze up.

Has anyone else had a similar problem with one ...looking for some guidance!

Thanks,

Darrell

Tech255
New User
Posts: 11
Joined: Sun Mar 26, 2017 4:51 am
What radios do you own?: Yaesu FT757 mk1 FT-726r FT101Z

Re: Need Com 120A help .....

Postby Tech255 » Mon May 01, 2017 8:27 am

My com120a ccasionally shows the input overload fault i think there is a temperature sensor in the input duplexer module located in the rear of the unit, if you can get it to work for a while go into the self test menus and there is a test for battery and temperature i think this is the input sensor as mine shows a very low minus temp which slowly rises if it goes too far the machine shows the fault. On off problem no idea im afraid..

Audiotron
New User
Posts: 43
Joined: Wed Apr 05, 2017 5:51 am

Re: Need Com 120A help .....

Postby Audiotron » Mon May 01, 2017 2:21 pm

Hi ,

I already got a fault on the 120B that one of the keys was stuck consecutively locked any command including ON/OFF

Darel
New User
Posts: 8
Joined: Tue Jan 03, 2017 7:19 pm

Re: Need Com 120A help .....

Postby Darel » Mon Jun 05, 2017 11:33 am

To be a bit more specific now that I have tried it a bit more ...

If I turn the unit on from the back switch it will power up and stay in the self test mode ... I can then push any one of the front buttons, rec, gen, etc...and the unit seems to work fine. If at any time I push the "power" button in front the unit will freeze up and I will have to shut it down from the rear switch .

Can anyone steer me in the right direction to troubleshoot this problem?

Thanks,

Darrell

Audiotron
New User
Posts: 43
Joined: Wed Apr 05, 2017 5:51 am

Re: Need Com 120A help .....

Postby Audiotron » Mon Jun 05, 2017 12:28 pm

Hi

Your problem is on the front keyboard, typically Matrix error disassemble it and see if the keyboard conductive ink has not been deposited on the conductive surface of the board..


Best Regards

Darel
New User
Posts: 8
Joined: Tue Jan 03, 2017 7:19 pm

Re: Need Com 120A help .....

Postby Darel » Wed Jun 07, 2017 12:32 pm

Having never taken one of these apart before, what kind of a job is it to access the front keyboard?


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