mixer repair - Page 1
Forum section: electronics / repair

author: paulhm81
author_rank: Regular Contributor
timestamp: July 21, 2014, 12:34:28 pm
content: Hello everyone. I received for repair a BEHRINGER KENYX X1222USB with a small problem - only one channel works. I have no experience repairing mixers and from what I see it's mostly op-amps. It doesn't matter what the input channel is, the output only works on the left channel. The right channel has no output and the graphic eq only shows activity on the left one as well. Please advise me where I should begin to look for the problem. 10x

author: wiss
author_rank: Frequent Contributor
timestamp: July 21, 2014, 01:03:06 pm
content: 1: Not worth the effort, buy a new one, not behringer, Yamaha has good ones, MG124 for example.2: Ok, you do it for the fun of it... On my old 1832 many of the faders gave up and behaved really strange, very attenuated sond on left main out when using unbalanced out, worked with balanced out (?!?!)

author: N TYPE
author_rank: Regular Contributor
timestamp: July 21, 2014, 01:27:13 pm
content: Its definitely worth the effort.. Why give up so easily?So the signal is not reaching the graphic EQ so you know that the problem is somewhere between the input and the eq.You're really going to need a scope to troubleshoot this bit of hardware, dont really need anything fancy just something which will allow you to view a waveform try searching for some schematics and service documents for that model - i wouldnt be surprised if you cant find anything, but you may get lucky and find one.. even if you have to pay for them it'll be a big help.Basically you want to start scoping the right channel audio signal at the input and try to follow it through the circuit until you see something fishy, you can test the left signal path to verify if you've found the fault or following a red herring.get some kind of constant frequency sine wave signal to pass through the mixer to make it easier to scope out either from a func gen, or build say a 1khz oscillator or even download a tone generator app on your phone and connect that to the mixer input.I dont know that much about audio equipment repairs but thats where I'd start.Check your input jacks solder joints to the PCB and any other obvious visual stuff like that too...

author: rob77
author_rank: Super Contributor
timestamp: July 21, 2014, 01:53:27 pm
content: if you don't have a scope, the use one of the soundcard oscilloscope apps for your computer.. and as suggested use your phone as tone generator (or again the soundcard of your PC).

author: wiss
author_rank: Frequent Contributor
timestamp: July 21, 2014, 02:03:25 pm
content: Quote from: N TYPE on July 21, 2014, 01:27:13 pmA new one is (overpriced at) 170 eur from thoman.de and (the 1832 anyway) is built out of "many, many"-layered boards, you will need lots of heat to remove anything

author: paulhm81
author_rank: Regular Contributor
timestamp: July 21, 2014, 05:10:24 pm
content: I have a 100M analog scope. I was wondering if it would be a bad idea to desolder an op-amp from one of the channels and replace the one from the master volume that is not working. They are the same. I don't know how to check an op-amp but maybe I will try tomorrow. I mislead you in my first post because I said something about graphical eq but I meant to say the leds that show the volume/power. It has nothing to do with the eq. It's as if the right channel isn't getting any signal. I will download the datasheet for those op=amps to identify the pins and I'll check the supply voltages and if anything is getting in or out.

author: wiss
author_rank: Frequent Contributor
timestamp: July 21, 2014, 06:45:04 pm
content: Typically, a non-functional opamp will have different voltages on the 2 inputs, compare with offset voltage spec in your datasheet.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 21, 2014, 06:52:20 pm
content: If you can get a schematic (or even better a SERVICE MANUAL) for it, then it will be easy to trace the signal to see where it disappears.Without a schematic, the complexity combined with the low replacement cost make the repair option a much less viable proposition.You could conceivably trace the signal with nothing more than an ice-pick or a screwdriver. Of course, if you slip and short out separate nodes on the PC board, you have an excellent chance of damaging it further. Since there are no hazardous voltages inside (assuming you have enough sense to stay away from the power supply!), you could work back from the right channel output, connecting it to an amplifier and speaker. You should be able to hear hum/noise by touching the input to the circuit that drives the output connector. If that is OK, then proceed upstream to the next stage and keep doing that until you find the interruption to the signal. The problem is somewhere between the right channel output and the right mixing/summing bus.When you say "the output only works on the left channel" do you mean only the main right channel output? Does the right channel work on the USB output? Does the tape in work only on the left channel? Even a small mixer like this has several different signal paths. Have you checked out ALL of them?

author: OilsFan
author_rank: Regular Contributor
timestamp: July 21, 2014, 06:53:18 pm
content: Behringer has a bad reputation and yep they are low cost but those Xenyx mixers are not bad at all. I'd have a go at fixing it. As mentioned, best bet would be to inject a signal and use your scope to find the point where it all goes wrong.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 21, 2014, 07:18:41 pm
content: I was going to say output stage. Or, anything leading up to that, e.g. mute circuit, master volume, etc.Tim

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: July 21, 2014, 07:46:02 pm
content: I don't see any test points on photo. Are there any test points on other side of the board?In addition to output stage I think it make sense to check balance control slider at the front - everything mechanical that moves tend to die first. Also since this thing has multiple outputs I would check if all outputs have same problem.What killed it? Wrong impedance plugged into output or coffee spill?

author: wiss
author_rank: Frequent Contributor
timestamp: July 21, 2014, 08:23:16 pm
content: Quote from: Richard Crowley on July 21, 2014, 06:52:20 pmEehhhum, I did find the service-manual for my MG166 on google a few weeks ago....I'd guess the behringer service-manual will be a map to the closest electronics-recycling-depot...Even if you repair it it will very likely fail in the future again, and you don't need to spend 1000 eur on a good mixer, just about another 50% compared to this one.QuoteVery good point.To be fair! My behringer did sound perfectly good, for as long as it worked, no problems there.

author: paulhm81
author_rank: Regular Contributor
timestamp: July 22, 2014, 08:41:19 am
content: thank you for the inputI compared the pots on the left and right master volume and on maximum volume(lowest resistance) the good one has 1 ohm and the bad one has a few Megs. I will take one from the channels and replace the master one and at least it will work I hope.

author: IanJ
author_rank: Unknown
timestamp: July 22, 2014, 08:52:55 am
content: Hi,I repaired a Behringer mixer some time ago with the same symptoms. Turned out it was a dodgy slider. They are not really very robust.Ian.One side working only:Dodgy pot, easy fix:

author: paulhm81
author_rank: Regular Contributor
timestamp: July 22, 2014, 09:09:56 am
content: Quote from: IanJ on July 22, 2014, 08:52:55 amYeah, that was exactly the problem. I took one from the last channel and it works now. The owner said it didn't use that channel ever! Thank you all!

author: urbis
author_rank: Unknown
timestamp: July 22, 2014, 09:11:44 am
content: Quote from: wiss on July 21, 2014, 08:23:16 pmI don't see why you have to be so against someone repairing their product.Just because YOU don't like the product, doesn't mean that millions of other people don't like it too...

author: wiss
author_rank: Frequent Contributor
timestamp: July 22, 2014, 10:04:05 am
content: Quote from: urbis on July 22, 2014, 09:11:44 amSure, I'm biased, against anything this cheap with sliding pots, they will break again! Soon! Maybe within weeks...You`ll get plenty of exercise in replacing faders, a good one is 5 or 10 eur? If 10, those will cost you 130 eur alone.If you want a dirt-cheap mixer, go for one with rotary faders!

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 22, 2014, 12:03:56 pm
content: Behringer is everyone's favorite whipping-boy. I've never had any more problems with Behringer gear than with any other brand. IMHO, it is simply prejudice. If people throw gear around at head-banging rock concerts, then they deserve what they get. Bah.

author: David_AVD
author_rank: Super Contributor
timestamp: July 22, 2014, 12:19:05 pm
content: There's plenty of other brands out there that have the same quality (and worse) faders than Behringer's.Buying cheap is fine as long as you're realistic with your expectations of serviceability, support and performance.

author: wiss
author_rank: Frequent Contributor
timestamp: July 22, 2014, 01:13:19 pm
content: Quote from: David_AVD on July 22, 2014, 12:19:05 pmDo anyone know what brand they are? The faders on behringer that is.To me it seems that on a cheap enough mixer with linear faders (behringer or any other very cheap brand), after you unpack them you can not move them around at all if you want more then 2 years of operation out of them, even repacking and transporting in the original box is to subject them to physical abuse.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 22, 2014, 01:38:33 pm
content: The original cardboard cartons are NOT "road cases". They were originally designed for shipment from the factory, through a warehouse or two, and to the end-user. That is not to say that I don't do that myself (pack things around in their original boxes), but you must accept the risk if you choose to cut corners like that.

author: wiss
author_rank: Frequent Contributor
timestamp: July 22, 2014, 02:04:56 pm
content: Quote from: Richard Crowley on July 22, 2014, 01:38:33 pmThe original box, with the polystyrene packing should do an excellent job of protecting the knobs? They are not as strong as a wooden case but then I'm not talking about UPS-level of abuse hereMore like what you'd get from moving it around in a domestic setting (without cats, children and other violent beings) Neither am I talking about rock-club environment with a pint of beer poured over it once a week... Just taking it out of the box, placing it on a table for a weekend and then back into the box and into my car and back home.

author: IanJ
author_rank: Unknown
timestamp: July 22, 2014, 03:06:07 pm
content: Having been a bit of a soundman semi-professionally and having used the best of road gear (Nexo PA, Allen&Heath 32ch desk etc) I would never tell anyone to avoid Behringer. It has it's place in the market place and if you treat it with respect and according to it's robustness then it will last for many, many years.I have seen bands turn up to gigs with a Behringer desk in it's original cardboard box all tatty and torn, and when pulled out have sliders missing/bent etc. Those kind of folks deserve to have the thing quit for good mid gig.Ian.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: July 22, 2014, 05:03:12 pm
content: Quote from: paulhm81 on July 22, 2014, 09:09:56 amHaha, congrats, I knew it was a sliderEverything that moves dies first. Also these things frequently die after Coke/Pepsi spill - it does something irreversible to to them very fast.

author: paulhm81
author_rank: Regular Contributor
timestamp: July 22, 2014, 08:55:34 pm
content: I went a little deeper and I teared up the slider and I found a little piece of wrapped paper between the contact and the resistive lines. After I took it out and realigned the contacts because they were bent, it's working as expected. ~1ohm at lowest resistance.

author: wiss
author_rank: Frequent Contributor
timestamp: July 22, 2014, 09:07:49 pm
content: Cool! This time it seems to have been worth the effort!

author: urbis
author_rank: Unknown
timestamp: July 22, 2014, 09:12:04 pm
content: Quote from: wiss on July 22, 2014, 09:07:49 pmGood job he didn't take your advice then?

author: wiss
author_rank: Frequent Contributor
timestamp: July 22, 2014, 10:15:48 pm
content: Quote from: urbis on July 22, 2014, 09:12:04 pmWell, we're not there yetIn 2 years, tell me it is still working an you have proven me wrong!

author: IanJ
author_rank: Unknown
timestamp: July 23, 2014, 08:15:57 am
content: Quote from: wiss on July 22, 2014, 01:13:19 pmWell, here's a pic of the broken fader from my Behringer repair......maybe somebody will recognize it.Ian.

author: paulhm81
author_rank: Regular Contributor
timestamp: July 23, 2014, 09:00:25 am
content: the one with the paper in it is N D103 SOUNDWELL

author: paulhm81
author_rank: Regular Contributor
timestamp: July 23, 2014, 10:29:44 am
content: The problem is solved. It was a slider with a small piece of paper that got stuck and interrupted the circuit!