Need assistance with Behringer problem please

[IronCobra]

Hello,

I have a Behringer EURODESK SL3242FX-PRO Mixer. I've owned it for almost 3 years. I have an interesting issue however.

When I power on the board, it starts making a popping sound followed by a sound that resembles fireworks going off. I have narrowed it down to the effects processor but don't know how to go about getting it fixed. I did the effects reset by holding both effects buttons down and power cycling the board. It didn't work. Just for clarification, the sound is coming fron the board but through the headphones or monitors.

Please help if you can.

[Enzo]

Very hard to say. For starts, power off, open it up and remove the DSP board - I think it is about the size of a playing card. Pull it off and put it back on a couple times. This will clean the connector - the dual row of pins. Now with the dsp back in place, fire it up. Any difference?

The noises are only in phones and monitors? Not in the mains?

It could be the effects board itself, or it could be an op amp feeding the output from it back into the mix.

Get a list of what things affect the noise level and what don't. So we can isolate the problem. I'd be thinking a noisy op amp myself.

We can't provide schematics, but we can answer any questions and try to ident the part for you.

[IronCobra]

Very hard to say. For starts, power off, open it up and remove the DSP board - I think it is about the size of a playing card. Pull it off and put it back on a couple times. This will clean the connector - the dual row of pins. Now with the dsp back in place, fire it up. Any difference?

The noises are only in phones and monitors? Not in the mains?

It could be the effects board itself, or it could be an op amp feeding the output from it back into the mix.

Get a list of what things affect the noise level and what don't. So we can isolate the problem. I'd be thinking a noisy op amp myself.

We can't provide schematics, but we can answer any questions and try to ident the part for you.

Thanks for the response. Sorry for not being more clear. The noise comes through ALL outputs and can be seen on the peak meters. I even tried unplugging everything from the board and moving it to a different power source. I then would plug in headphones to all outputs and the problem was still present.

I will take it apart and check it out again.

[Enzo]

OK, it is everywhere, but still only with the DFX on? Or does the DFX just make it more noticable.

Remove the DFX, still noise? How did you narrow it down to the DFX?

Let us isolate. Turn all chanel faders to zero, all subs, and all masters, and the DFXs. Still noise? if so, look to power supply. That would be my first thought anyway.

If not, then turn up the masters only. Noise? If no, then turn up subs one at a time and assign to master. Noise? If no then start turning up the channels one by one. ANy associate with noise?

At the SMPS, scope each rail. There are +/-15VDC for the analog, +48 for phantom, and +5 for digital. Look for noise riding them.

My guts wants this to be a phantom problem. That would only show up with all masters and channel up though. if that is the case, try going to the molex connector from the SMPS to the mixer boards, find the pin with the +48, and release it from the molex housing. Tape it or something. Now with 48 removed from the boards, any help?

Think of the mixer like its block diagram. By turning controls up and down adn using the sends and returns as check points, isolate to what part of the thing is generating this noise.

[IronCobra]

OK, it is everywhere, but still only with the DFX on? Or does the DFX just make it more noticable.

Remove the DFX, still noise? How did you narrow it down to the DFX?

Let us isolate. Turn all chanel faders to zero, all subs, and all masters, and the DFXs. Still noise? if so, look to power supply. That would be my first thought anyway.

If not, then turn up the masters only. Noise? If no, then turn up subs one at a time and assign to master. Noise? If no then start turning up the channels one by one. ANy associate with noise?

At the SMPS, scope each rail. There are +/-15VDC for the analog, +48 for phantom, and +5 for digital. Look for noise riding them.

My guts wants this to be a phantom problem. That would only show up with all masters and channel up though. if that is the case, try going to the molex connector from the SMPS to the mixer boards, find the pin with the +48, and release it from the molex housing. Tape it or something. Now with 48 removed from the boards, any help?

Think of the mixer like its block diagram. By turning controls up and down adn using the sends and returns as check points, isolate to what part of the thing is generating this noise.

I have tried most of what you stated above. I thought it was the Phantom power but turning it on or off wouldn't change the problem.

I narrowed it down to the EFX when the Behringer tech told me how to reset the EFX on the board. When you hold down both EFX knobs while powercycling the board and it goes into reset mode, the noise goes away completely. If I turn down the effects volume the noise goes down but not completely away (I can still hear a faint popping sound).

And the popping and sparkling noise has reverb to it. It actually sounds like it may be a fault in the reverb.

[metalangst]

The DSP card is bad, You may be able to remove it and use the mixer as is. Try to get a replacement card from behringer,if not you may be able to exchange the mixer for a new one.

[Enzo]

At 3 years it is out of warranty.

I agree then it likey is the DFX board, but want to be absolutely sure. SInce teh noise revebs, that means the noise is either in the reverb or before it. The mixer's buffer feeding the DFX could be noisy for examlpe. That would be an example of the DFX controlling the noise , but not being at fault for it.

That is why I earlier suggested removing the DFX board to see if the noise went away with it.

I believe Behringer has the DFX boards in stock and you should be able to order one reasonable inexpensive from a Behringer dealer or servicer.

[jrfrond]

I believe Behringer has the DFX boards in stock and you should be able to order one reasonable inexpensive from a Behringer dealer or servicer.

The only way to get one will be from a scapped amp. A new one is a GREAT idea, but also a pipe dream.

[Enzo]

Well, I do have a number of them here, don't you?

But I have ordered and received DSP boards from Behringer in the past.

[jrfrond]

It's hit and miss with DSP boards. Like I said, we've taken them from scrapped units, which, incidentally, is the only way Behringer gets them too. If you DO get one, it means they scrapped a unit for it. It's like organ donation for amplifiers.

[metalangst]

Three years out of warranty, so what. Hit or miss, see what they say, who knows, you could end up with a new board.... or not. If the noise is from before the DSP, it would be on whatever effect is selected, not just the reverb. I have "repaired" many of these. all or most parts came from scrapped units, now as far as I know, all the returned units are shipped back to Maccau. It's just not cost effective to repair a behringer.

[Enzo]

It all depends upon what the Behringer unit is and what it wrong with it. I do a lot of repairs on them, I am one of their regional service centers. We scrap a certain amount of them, but we also repair most. A blown power amp is usually a couple output FETs, bad jacks are bad jacks, noisy op amps, etc. And I still have all the dead units, they are not shipped anywhere. The central Behringer facility might ship things out for recycling with dealer returns and customer returns to them, but for me to ship some scrapped unit out would be prohibitively expensive in most cases.

And for the customer, you pay $400 for something, then $75 repairs are worthwhile.

Most manufacturers are flexible over warranty - if you are a week past warranty, few of them will cheap out and deny claims. But three years out, I don't know anyone who would replace a unit, but you are right, you can always ask.