I have a Behringer Xenyx 1622 FX mixer. The fuse blew, and now that I've replaced it (with the manufacturers recommended fuse), it does not power on when you flip the main power switch. The only instance of power going into the mixer is the +48v red LED, on the right side of the mixer, halfway up. The LED turns on when the phantom power switch is on, but not when the main power switch is on.
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.
Additional, if the fuse did not blow again, then the switcher must be running.
Verify the 4 voltages +12 and +/-15 and +5 volts.
One or more of those are probably bad. I would suspect the +5 volts.
I have seen arc over damage in Behringer mixers between the +15 to the -15 before. Usually this is NOT enough to take out the fuse...
Check C6, C9, C12, and C16.
Correction from first solution: There is NO -12 supply
These suppies all use 303 fast recovery diodes so if you find blown cap check D4, D5,D6, and D8 respectively for the above caps.
Note: the feedback to regulate comes from C12 (+15 unreg) that feeds back to the main switcher via an opto-coupler.
×
2,642 views
Usually answered in minutes!
×