behringer mixer ub1832fx doa

[mattball826]

new here, but frequent searcher and lurker. posted same in schematic area was pm'd to post here. idk

have a mixer with bad smps. not under warranty

unit was doa with couple blown traces on ac neutral line and ground. looks like some plugged into reversed line voltage (neutral side blown).

i changed out defective (shorted) rectifiers, bridge rectifier and rf line filter coil. also replaced the multipin smps driver ic. components from mouser.

unit comes on now, but pulsates. leds, etc all flash when powerd on.

there are small sm resistors that might be open near the optical fb chip, but i dont know the values. they have flash burns from where the foil pads were damaged. there was one shorted hr303 diode on the secondary of the smps, i changed all four to be safe

i can do smps repair but i need relavant values to know these small smd resistors etc.

any help is appreciated! thank you much

email to: dbs4568 at gmail dot com if you can please

[mattball826]

i have the 1832fx pro schematic, but there is no diagram for the smps. might have to go back to dealer and get another unit just to measure the values i suppose. i know i can buy these complete, but i already sunk in enough in parts+ shipping.

why would they not list the smps in their service manuals? odd

[mattball826]

problem solved.

was odd. unit after i replace parts was working when not connected to the chassis ground. dim bulb supply would flash, or sencore variac supply would show current up and down once you mounted smps to chassis.

this unit power supply took a hit on the neutral side and the ground from what they said an ac line was reversed. i think they meant the n and gnd were reversed on the receptacle.

after changing out the top245y, opto ic, bridge rectifier, and a couple of her103 diodes the unit had this weird issue. as i was testing without the smps housing grounded, the entire unit worked fine. eureka moment!! say the smps can work, unless grounded.

so what was not proper here? after inspection i found the top 245y was not insulated and case was going right to chassis ground. as soon as the chassis was mounted, that drive ic was right to chassis gnd too.

this unit had to have been serviced elsewhere even though the customer said it wasnt. insulators don't just fall off of parts. come to find out, this particular insulator wraps completely around the top245y smps driver. funny because the bad top245 chip had heat sink grease all on it.

i love when customers tell you their unit had never been opened up. no way this was factory since the unit worked for several years.

hope this helps anyone working on these smps units. think simple and those common sense problems (like missing insulators or component boots) are not as time consuming. i would have posted this sooner, but wanted to see if unit lasted 7-10 days after pickup. unit is fine.

[Jazz P Bass]

problem solved.
this unit power supply took a hit on the neutral side and the ground from what they said an ac line was reversed. i think they meant the n and gnd were reversed on the receptacle.
.

Glad that you got it fixed.
I avoid Behringer stuff like the plague.
That comment about the "N and G" being reversed does not make sense.
At the mains panel, both N & G are connected to the neutral buss bar.
The G is a separate path that will open the circuit breaker if the equipment chassis comes in contacxt with the live wire.

[mattball826]

the guy used one of those testers with the 3 neon bulbs at the place. he said it had reversed n and grnd, but he might have meant to say h and n since thats that only tester indication im aware of other than open circuit lamp readings..

im not afraid of smps. been around them since my tv days. things can get ugly fast if you don't pay attention. what scares me more are the units (like guitar amps) that have been around and serviced, diy for x amt of years. never know what to expect.

guy with this behringer unit had to have taken it somewhere else, or attempt diy fix. no way that boot insulator was off of that unit. i make bet orig problem was just the one diode her103 on the smps output supply (only shorted diode there). guy working on it did not know about smps, and he connected maybe test equip that was not isolated and that blew foils and teh smps driver components at neutral and gnd side.

i was surprised to see any pro sound audio gear using smps. there are so many venues that have bad wiring from diy stages at times, smps are not friendly to that.