Behringer mixer - UK Vintage Radio Repair and Restoration Discussion Forum

Malcolm G6ANZ · 26th May 2011, 8:26 pm

Behringer (Xenyx) 1222fx mixer.
I’m not sure if this should be in ‘modern equipment’ or here. However….
I was given this mixer to fix after the right hand channel had stopped after some (quote) ‘mix up with cables’. Sure enough there was no output on one of the balanced pair on the right channel.
A look on the internet for a circuit yielded no results, a request on this forum and I had a circuit within the hour. Thanks Baz much appreciated.
The balanced output is from a pair of dual channel audio IC’s. Scoping them in turn, when I had found them on the pcb, showed that one of them was at –ve. As these are surface mounted devices I wanted to be certain that the IC was faulty before condemning it. To this end I removed to input and output coupling capacitors which were not surface mount. The output was still at –ve.
Ordered four pin compatible devices from CPC , the original not being available as SMD, and proceeded to change the faulty device. As I had been warned in the forum that the PCB track can lift easily, I cut the legs off the IC and removed each pin in turn. This way no track was overly heated. The marking for pin 1 on the new IC was almost invisible and could only be seen under a magnifying glass with lots of light casting a shadow. I convinced myself which one was pin 1 and held the IC in place and tacked a couple of pins down. I then soldered the pins down properly.
The capacitors I had removed were replaced and power re applied. Success, there was a signal on both of the balanced lines on the right channel.
This was one of the faults where a circuit is essential as it is impossible to trace the circuit from the PCB, so my grateful thanks to Baz for the circuit and to others who offered advice.
Sorry about the lack of photos
Malcolm

gezza123 · 26th May 2011, 9:37 pm

HI: Malcolm,it may be a bit simular to the one I have is a UB1832FX.
Yours has a usb ,mine don't but the inputs may be the same.PM.me Gezza.

26th May 2011, 8:26 pm	#1
Malcolm G6ANZ Octode Join Date: Feb 2006 Location: Bristol, UK. Posts: 1,041	Behringer mixer Behringer (Xenyx) 1222fx mixer. I’m not sure if this should be in ‘modern equipment’ or here. However…. I was given this mixer to fix after the right hand channel had stopped after some (quote) ‘mix up with cables’. Sure enough there was no output on one of the balanced pair on the right channel. A look on the internet for a circuit yielded no results, a request on this forum and I had a circuit within the hour. Thanks Baz much appreciated. The balanced output is from a pair of dual channel audio IC’s. Scoping them in turn, when I had found them on the pcb, showed that one of them was at –ve. As these are surface mounted devices I wanted to be certain that the IC was faulty before condemning it. To this end I removed to input and output coupling capacitors which were not surface mount. The output was still at –ve. Ordered four pin compatible devices from CPC , the original not being available as SMD, and proceeded to change the faulty device. As I had been warned in the forum that the PCB track can lift easily, I cut the legs off the IC and removed each pin in turn. This way no track was overly heated. The marking for pin 1 on the new IC was almost invisible and could only be seen under a magnifying glass with lots of light casting a shadow. I convinced myself which one was pin 1 and held the IC in place and tacked a couple of pins down. I then soldered the pins down properly. The capacitors I had removed were replaced and power re applied. Success, there was a signal on both of the balanced lines on the right channel. This was one of the faults where a circuit is essential as it is impossible to trace the circuit from the PCB, so my grateful thanks to Baz for the circuit and to others who offered advice. Sorry about the lack of photos Malcolm

26th May 2011, 9:37 pm	#2
gezza123 Heptode Join Date: Mar 2010 Location: Eastham, Wirral, Merseyside, UK. Posts: 788	Re: Behringer mixer HI: Malcolm,it may be a bit simular to the one I have is a UB1832FX. Yours has a usb ,mine don't but the inputs may be the same.PM.me Gezza.