IFR COM120A rf power meter faults

[Tech255]

I have a com120a with a few issues the initial test shows 3 failures deviation, distortion and power meter its the power meter im more interested in,
I have checked the digital board and found capacitor problems I've replaced all the electrolytic's and the lf412c's as one of them was badly corroded the spectrum analyser shows the correct power level so not sure why the power meter dosent I would have thought they were linked.
also I have the code to get into the calibration menu but I was wondering is there a separate calibration manual or is it all in the service manual, and how do I go about purchasing one?

[Audiotron]

Hello Friend

I tried contacting this email : info@cobham.com , Not yet replied !!
but it is the only contact I unfortunately have of Aeroflex

I believe they can still sell the Manual Service for this equipment.

Good repairs, Hugs

[jry]

short answer is that the calibration and alignment is in the service manual.( I have about three or four versions of the COM-120 service manual and it's in most of them ...the COM120C supplement is not a full SM if you find that one )

Usually the self test failing implies more than just an alignment issue but the alignment process may help isolate the problem.

[Tech255]

short answer is that the calibration and alignment is in the service manual.( I have about three or four versions of the COM-120 service manual and it's in most of them ...the COM120C supplement is not a full SM if you find that one )

Usually the self test failing implies more than just an alignment issue but the alignment process may help isolate the problem.

Dont suppose you could let me have a copy of the pages that relate to the calibration could you, or is there too many.

[Tech255]

Wowbagger
I just found a post from someone else with the same problem with a com 120a devation, distortion and i also have power meter problems and you asked him to set the machine as though it were doing the self test in duplex mode i have done this and the results were as follows.

Deviation 1.1khz
Af freq 1khz
Distortion ---%
Rf power 0.0mw
Rf freq err 0

I have replace the caps and lf412c ics on the baseband tray, can i assume there are still faults or will calibration bring it back.

[Wowbagger]

The fact that the distortion isn't reading at all suggests there are still problems - check for a trace that got eaten by the electrolyte from the caps.

[Tech255]

I have finally recieved an answer from aeroflex it seems my request for a service manual has gone all around the uk but to no avail kelly johnson finally emailed me back to let me know there were none anywhere not even a pdf copy she suggested trying the usa so i have emailed them but dont hold out much hope. So if anybody on here has a copy of the service manual for a com 120a i would be very interested.

[Tech255]

Update to my last post just had confirmation from usa office none available there either. Bummer!

[Audiotron]

Hi friend,

I also look for these manuals, but until today I did not succeed, after all information of these units are very well received I recover them bad always have defects that are necessary to use the service manual, and a pity there is not something that is for help.

Hugs

[Tech255]

Wowbagger

As you can see from my previous posts service manual unavailable anywhere i know you are designer not repairer but if you have any contacts that are able to supply a copy of the 120a service manual or even just the pages that relate to calibration i would be eternally grateful
Thanks

[Wowbagger]

What do you need - just the calibration procedure, or actual schematics for repair?

[Tech255]

Wowbagger

If you can only get part of the manual i would prefer the calibration section but if the schematics are available i would like them yes, thank you

[Wowbagger]

I don't have the service manual (I thought I did, but I didn't get it when I was getting manuals). But I can help on how to do the calibration, since I wrote most of that code.

[Tech255]

Wowbagger

Ok thanks i do have the calibration access code and ive had a look around in there but before i start that i need to finish repairing the baseband caps leakage problem.

You suggested this little routine to someone else does this check everything on the board or are there any other little sequences that could help.

Duplex mode, TX freq 105 MHz, RX freq 105MHz + 2.5 kHz, output TR -40 dBm, input TR, no attenuation.
Gen 1 to FM mode, 3 kHz deviation, 1 kHz rate, triangle wave.
Receiver FM, 15 kHz IF.

Ive also noticed something else i think is a bit weird my unit has a tracking generator if i take the output and feed it into my spectrum analyser it shows a nice rf signal, and if i use another generator to feed into the analyser on the com120 it shows a nice rf signal but if i link the in/out ports on the 120 i just get a line accross the screen at the rf level used.

[Wowbagger]

In what mode? Analyzer, or Duplex? In Analyzer, that would be the tracking generator, which would show up as a "Track Gen" field in the lower right.

[Tech255]

Wowbagger
Put the ifr back on the bench today, i recently bought a nice quality rohde & swartz cmu200 so ive been playing with that.
Anyway turned the ifr on and after self tests it showed the usual 3 failures i pressed the gen button to check what was working and then the screen started flashing on off then i got an alarm and it told me there was an rf though there is nothing connected is this alarm controlled from the baseboard as well could it be capacitor damage giving me this alarm?

[Wowbagger]

That would be my guess, unfortunately.