Behringer Xenyx 1222FX won't power on, only phantom power

Hi,I was jamming yesterday and while playing not very loud the mixer went off and never worked again,also cut out the stereo amps I was using to power big speakers,been using it for about 5 hours one a week for last few months with no probs,Q:is there a fuse inside that may have blown? There was a 3amp in the normal plug which stated 5amp but worked fine for ages,I replaced it with another 3amp seeing I didn't have a 5 amp but no power,have you any ideas what to do because I need this working quick and can't afford another one,it's a behringer xenyx 1222fx mixer. Any help would be amazing Thanks Mike

Here is a schematic close to your unit:

http://elektrotanya.com/behringer_xenyx_1622fx.pdf/download.html

Scroll down to "get manual" and click to download. Ignore other download links.

The phantom power is a separate rectifier and regulator. See page 11 of the download service manual for the power supply. Be careful when working on line operated switching supplies. I suspect you will find one of the other supplies is dead. If the phantom is OK, then the switcher is working and one of the rectifier/filter/regulators is bad. Check if an electrolytic cap is shorted.

The board is a mixer only, not an amplifier. A mixer simply, well, mixes audio sources into a line output which then goes to the amplifier. Your question really has no answer since wattage is determined by the amplifier used. Essentially, it can "push" as many watts as the amplifier can deliver.

Don't know what you are saying. Phantom power is only used for Condenser mics and a few DI boxes. Make sure you ONLY use TRS or XLR cables into ANY/ALL inputs when using Phantom power. Please describe what you mean by :some channels decide to come". ONLY change Phantom power when system is off as you will get loud noise often by switching phantom while live.

The Phantom power comes from a seperate winding on the switching power supply.Likely one or more of the other voltages are not present due to a failure of one or more components. The supplies are current limited so a short anyplace on the board may cause the problem. I had one of these short betwen the +/- 15 volt busses because somebody spilled liquid into it.

Here is a close schematic... a slightly different model with less channels, but circuoitry is the same, just more copies of it in yours: I believe it is zipped with four files... the last is the power supply.

http://elektrotanya.com/behringer_xenyx-1222fx_v1000_dpm5m_ub-spsu2_sch.zip/download.html

The phantom power light wouldn't illuminate unless the unit was powered on. Possibly the main power indicator light is burned out.

You should find +/-15 volts and +5 volts as well as the phantom power... but that light can come on at much lower than desired voltage.

Note that the regulators are current limited so a short on the mixer board can kill one of the voltages.... but you are not getting any input from teh switching portion of the regulator so the switching part of the supply is apparently dead. To replace the supply you would have to call Behringer at 1-425-672-0816 to get the part number and an incident number and then call FullCompass which is their part distributor now.

When working on a switching power supply, use an isolation transformer for safety and use a 60 watt lamp in series with the power cord to limit current during testing.

The circuitry will be SIMILAR to the power supply found on page 9 of schematic you can download at:

http://elektrotanya.com/behringer_ub1204fx_pro.pdf/download.html

First thing is to evaluate configuration you had when it failed.

A common mistake is to have power amplifiers powered from receptacle at one end of a room and mixer at the other. This can lead to ground loops that fries components. Always power interconnected devices from the same source of power.

Be aware that the 1/4 inch main outs are balanced TRS and plugging in a mono cable or even a balanced TRS at the mixer that gets shorted at the amp end is a no-no.

You didn't include any info for us regarding your interconnects, etc.

After reviewing the schematic, I don't understand how the Phantom power can REMAIN on with the power switch off... this CANNOT occur except for what energy is left in the 48 volt supply filter cap... This might last for minutes after the fuse went... UNLESS you have devices connected which are backfeeding the 48 volts. (which would be a disaster)

The 48 volts, +/- 12 volts and +/- 15 volts and the +5 volts ALL come from the SAME switching power supply. I suspect one of the filter caps went or the primary switching regulator a TDP245Y chip.

You should ONLY work on the line side of this using an ISOLATION transformer since the line side has lethal voltages.

To do testing, one replaces the fuse and puts a 60 Watt light bulb in series with the hot side of the inout line. The lamp "acts" as a resetable fuse and limits the current for testing. When all is well again, the lamp will remain out with the power flowing through it.

The D1 diode bridge and C7 input rectifier and filter are first things to check. You can do those with an ohmmeter.

I will caution you to ALWAYS power any and all equipment from the SAME power source. Plugging in devices from across the room will set up ground loops and any ground fault will fry equipment.

Use four (4) TRS cables. Connect from the
AUX "send" (left and right) to the input of the effects unit with two of the cables. Use the other two cables to connect from teh effects out jacks to the AUX "returns" left and right.