Hello there, I am having trouble with the signal for my Line inputs on the Behringer UMC22.

You should be able to unplug a mic from the xlr input with the unit on with no problem.
I beleive the problem is that the xlr input jack has one or more legs broken off the board. If you dsassemble the board and resolder the three legs to the board you'll probably fix the problem.

Ground the 3rd pin! :)

Sounds like the output cable from the 802 is not correctly pinned to your input on the computer. Fred is on the right track but you may need to take it a bit further.
It may also be helpful to use a Pro USB audio interface such as the Digigram UAX220v2 (line level version).
If you wish to use the computer's on board sound card consider an IHF/Pro interface that converts balanced audio to unbalanced , and the proper cables. Two 3-wire balanced 1/4-inch from the 802 to the left and right inputs of the interface (XLR Male), then RCA (Red and White) to a 1/8-inch TRS Plug cable onto the the computers audio input.
Henry Engineering's Matchbox HD comes to mind.
Good Luck.

Greetings! Ok, your amp has an XLR (3-prong) Low-Impedance input on Channel 1 for a Mic. All the other inputs are 1/4" High Impedance inputs, which are for instruments and/or other High Impedance items including low quality High Impedance Microphones. The SM48S is a high quality Low Impedance microphone, so if you use it with a 1/4" plug, it will be in a High Impedance channel, and will be very LOW in volume in comparison with everything else. So, you must use an XLR (3 prong) cable from the Mic to the Channel 1 input on your amp. That will do the trick. Good Luck with your new amp and Mic!

Make sure your mic cables are XLR to XLR and not cheesy Karaoke type cables with 1/4 inch mon plugs on the end. Please note that I have found some mic cables with wiring errors. They had the shield and one of the signal lines reversed. please verify that your XLR mic cables are wired with:
Go to thiis site and verify your cables:
http://www.toffer.com/wp/2008/08/07/3-pin-xlr-wiring-diagram/
Please note the pin numbers as they may not be what you expect. Ground is actually the shield or braid and the red and black are twisted pair signal lines.

Without knoowing what type mic you have and where it is connected we can't help you. Normally a mic is connected via an XLR to XLR cable to one of the input XLR jacks. Then you turn up the top white knob... start at about 3 o'clock. This is the input trim control. Set the grey pan control in that same line of knobs to 12 o'clock. Move the slider up for that column AND move the MAIN slider up.
The speaker should be in the A/B mode for stereo. With these settings you should get mic output.
Please view videos on YouTube about "mixer setup". MOST mixers are about the smae and what you learn about any of them will apply to your unit. One other thing is IF you are using a CONDENSER type mic, you will need to turn on the PHANTOM power switch. Note condenser mics are so sensitive that they must be used in a studio as if they can hear the speakers at all, feedback will occur. Also be careful if your speaker plugs are 1/4 inch, do NOT lett the sleeve of channel A touch ground as the sleeve, not the tip is hot.

Has somebody spilled liquid into the unit? Are you using XLR to XLR mic cables? If using condenser mics you need Phantom power on else NOT.

If the faders are noisy, use CRC226 in them. You can get that at Home Depot in the electrical dept.

NEVER use contact cleaner such as Deox.it or BlueShower in faders... it wrecks them

Personally I would run the RCA outputs to the RCA in on the APS.
If you insist on using XLR from the APS to the board (like through a snake etc) I would higly recommend using XLR to 1/4" adapters. These things have wonderful little transformers in them (yes, wire wound transformers) that do the 1/4" to XLR conversion really nicely so that you can run your signal through the snake or just so that you don't get the hum and distortion that can be associated with unbalanced signal transfer.
You want a HI-Z unbalanced to LO-Z balanced adapter.
Not always easy to find, but if you absolutely cannot locate any, I have a couple in stock.
I suggest you look around though, because mine aren't cheap!

The XLR mic connector is a board mounted part... You will not like the effort to replace it as most of the hardware must be removed from the panel to allow the circuit board to be removed so you can swap the XLR connector. Getting parts from Behringer is time consuming... but may be the only way to insure getting compatible one. Call Behringer to get their part number at 1-425-672-0816
The order from Full Compass... expect it to take a couple months as their repair parts chain is really slow now.

You can't do any damage... just try plugging into the line... If the mic has enough output it may work. Balanced line mics are best though...