Soundcraft Spirit LX7 Noise issue

[DuckJordan]

At my venue we are getting a few strange noises. The first of which came when we turned the system on we were getting a 60hz hum out of our main cluster that nothing we did (except turning the amp/eq/board off) would fix. The next noise that is in question is a mechanical tick we sometimes get going through our booth monitors. Lastly we will get a hum out of our cluster with absolutely nothing on the board on.

Both me and our TD have come to the conclusion of a bad power supply on the Spirit. Since the board is 8 years old we were just going to suggest to the Director to purchase a new sound board next year.

I would like your suggestions on what could be causing these problems.

PS. side note the only sound that is constantly there is the hum our of cluster that sounds like static. The others are seeming to be at random times.

 

[Morpheus]

At my venue we are getting a few strange noises. The first of which came when we turned the system on we were getting a 60hz hum out of our main cluster that nothing we did (except turning the amp/eq/board off) would fix. The next noise that is in question is a mechanical tick we sometimes get going through our booth monitors. Lastly we will get a hum out of our cluster with absolutely nothing on the board on.

Both me and our TD have come to the conclusion of a bad power supply on the Spirit. Since the board is 8 years old we were just going to suggest to the Director to purchase a new sound board next year.

I would like your suggestions on what could be causing these problems.

PS. side note the only sound that is constantly there is the hum our of cluster that sounds like static. The others are seeming to be at random times.

if it sounds like static, then it's a gain structure issue.

Otherwise, is yours the lx7ii or the original? I had heard that the PS in the original wasn't that great.

 

[DuckJordan]

It's the origional, i have another thought on the static it could be from our feedback exterminator which is a peice of junk that should have just been an eq, but we have to bring in a real time analyzer to get it set properly again, that could be allowing some of our static problem to come through.

 

[Morpheus]

It's the origional, i have another thought on the static it could be from our feedback exterminator which is a peice of junk that should have just been an eq, but we have to bring in a real time analyzer to get it set properly again, that could be allowing some of our static problem to come through.

well then, try disconnecting it from the chain, and see if it goes away...

The 60-cycle indicates a ground issue, (usually on the audio, not the power)... try swapping out some lines, and make sure you are using the right cable (balanced/unbalanced)

 

[DuckJordan]

well then, try disconnecting it from the chain, and see if it goes away...

The 60-cycle indicates a ground issue, (usually on the audio, not the power)... try swapping out some lines, and make sure you are using the right cable (balanced/unbalanced)

On the ground issue i've heard from a lot of people that the bad power supplies will cause power bleeding, the reason why i think it wouldn't be a bad audio line is because the board is muted when the sound is happening. nothing on everything muted.

 

[Morpheus]

On the ground issue i've heard from a lot of people that the bad power supplies will cause power bleeding, the reason why i think it wouldn't be a bad audio line is because the board is muted when the sound is happening. nothing on everything muted.

Try wiggling the lines off the board, see if there is a broken/intermittent shield issue...


although, what I've heard, 8 years is pretty good for the original lx7...

 

[FMEng]

It could be the console power supply, but it could just as easily be a simple ground loop in the audio cabling. Ground loops usually make a fairly smooth 60 Hz hum. Failing power supply capacitors usually make more of a buzz. A buzz is raspier because it has more harmonics of 120 and 360 Hz.

Another way to tell is to listen to the console with a pair of headphones. If the hum is there at significant levels, with all inputs and outputs disconnected, it is a power supply issue. If the hum is there when cables are connected, and goes away when cables are disconnected, it's a ground loop in audio wiring.

If you never hear the hum from the console headphone jack, then it isn't likely the console. Then, start looking further up the chain toward the speakers.

If it does prove to be the console power supply, it is quite repairable.

 

[DuckJordan]

the hum stays when all the levels are down and the headphones are plugged in. even if it is repairable it would cost us much more to get it fixed than to pay for a new console. Being a public school any repairs have to go through a bid selection then they must be investigated and finally actions taken, in the area there is only one certified repair shop for the LX7 and he is unfortunately quite expensive. there are also other thing wrong with the console so the school will most likely just replace it than repair it.

 

[bishopthomas]

The key is UNPLUGGED. Make sure there is not a single cable on the input or output side of the console. If it is still noisy then it is the PSU. If it goes away then it's a ground loop. Start plugging back in, starting with the outputs and use process of elimination. Buying a new console might be a good thing to do anyway, but if your problem is not in the LX7 then you'll have the same issues with a new one.

You said the problems started "when we turned the system on," but the console is 8 years old. What changed in your system that would have caused this? Is this a new setup, did you repatch some cables, swap out amps, plug something else in to AC? Or you just came in 8 hours later and mystery noise?

 

[DuckJordan]

the biggest problem with you saying it might be a ground loop is IT IS NOT A CONSTANT NOISE IT COMES AND GOES RANDOMLY, i have stated this before if it was a ground loop the noise would stay as long as no cables were touched.

So it is not a ground loop, I may be a student but i am not an idiot i have worked with this system for 4 years, i know it inside and out.

 

[bishopthomas]

So it is not a ground loop, I may be a student but i am not an idiot i have worked with this system for 4 years, i know it inside and out.

You didn't answer any of my questions that would help me (us) diagnose your mystery noise sight unheard. So go buy a new console and hopefully all will be well. I tend to think of ways to fix things without throwing money at it, but I guess it's different when you can just go ask the boss for a new one...

 

[SHARYNF]

Just because the sound comes and goes does not eliminate a ground loop. it could very well be that there is another device somewhere else in the system tied to the ground that is intermittent. Ground loop does not have to be constant. even tough it Typically it is but not always.

It also could be failing component in the mixer that could be heat sensitive or could be a loose connection

It is unlikely that fixing the problem is going to be more expensive or as expensive as replacing the board.

Just because people don't agree with you or offer additional questions does not make them think you are an idiot. But if you do react to peoples attempts to help they way you have in your response, you are not likely to get much help in the future.

Sharyn

 

[Kally123]

"Just because the sound comes and goes does not eliminate a ground loop. it could very well be that there is another device somewhere else in the system tied to the ground that is intermittent. Ground loop does not have to be constant. even tough it Typically it is but not always"

As SHARYNF states ground loops can come and go. If you have a system that is not isolated for ALL of the sound equipment then you have a greater potential for loops. I have been mixing on several different soundcraft boards, older discontinued Venues, a K3 Theater, Lx7, and Lx7ii, now for about ten years. I have run into all of the problems that you have mentioned.

I have also chased all the gremlins, yes I am intentionally being vague, that every body has suggested that you look for. And since I have been down the troubleshooting road with many different Soundcrafts I can tell you that it is most likely a combination of the power supply and the age of the deck. The age is esspecially importtant if the deck has not been properly cared for. Every Soundcraft deck that I have used has outlived the power supply and every deck has also needed a good inspection and cleaning out right around the age range that you are talking about.

Soundcrafts are good decks and you can get a long way with them but if you do not take care of them they will bite you. The cliking that you discribed indicates that there is some issue with the logic components in the board. And if the power supply is giving out then that is were it will show up first. Sound crafts power supplies are very very finiky and if they do not get clean power over an extended period of time they will give out on you, and they ussually do it over time and not all at once.

Good luck and I hope you find your answers.

 

[DuckJordan]

sorry about snapping yesterday, The ground loop you are saying should not be the problem as the noises come almost immediatly after the system is turned on in the last 3 times we have turned the whole system on it has not made any noise what so ever, also i am very aprehensive on a problem with not all the components not being on the same power supply, the power for our auditorium is run through one ground, it is also tied in to our lighting which goes directly out to the outside transformer. so all of our power is coming from the same source. The reason why i think it would be the board is yes from what i've heard the power supplies on soundcraft boards tend to be very sensitive.

The reason why i state it would be more expensive to get it repaired is we are in a public school system. Which inhernently means that anything we do first goes to the principal then to the district head, they decide from there what to do. Our provider who installed our system 20 years ago did not do a very good job (both on the contractors side and the audio installers side). we have had them in to our building before and they have messed with things that were fine and didn't need to be fixed. which ultimatly cost us more money to get properly fixed because the "repair man" who came to fix our problem caused more.

So in my situation would you allow a complete stranger who "says" they know what they are doing mess with your system, coming from the same company who messed up your system before, "fix" your soundboard, or would you spend $1,500 on a new board for the room in which you could easily do yourself?

Personaly, in my knowledge of our situation in which we haven't changed anything, would suddenly start causing problems. our amps are all new as of 4 years ago, QSC's and crowns, I trust those companies very well and the oldest part of our system is our center cluster and our pre-amp rack which hasn't given us any kind of problems. Right now our weakest link in the system would be the soundcraft LX7.

So upon deduction which would you in your situation do? Spend $500 to get the same result from a "knowledgable" person, or spend $1,500 on an updated board that might be able to better teach students on?

 

[SHARYNF]

Understand the situation

I guess it would try to narrow down the cost, and then if it were a toss it out situation I probably would look at the powersupply my self and replace the Capacitors, and look around inside the mixer to see if things and come unseated or if there were any obvious problems

Sharyn

 

[DuckJordan]

if i were more comfortable with the soundboard and had the replacement on hand or had the money for the replacement on hand i would do so but seeing as how it has to work for at least another year i am very apprehensive about doing that.

at this point in time all i can do is try and see if there is a more easily accessible solution available or work with it even with its occasional mess ups until they can get a replacement.

I was just hoping someone else had other ideas than what i have already checked and tested.

 

[SHARYNF]

Typically it is the power supply BUT these are designed with one LARGE circuit board and if the mixer has been abused it is possible that the board has a crack in some of the traces.

Really hard to tell, as others have said these are not the most robust mixers out there

Sharyn

 

[DuckJordan]

Thanks for your advice i will post more once i get a final verdict from the higher ups

 

[jkowtko]

Two things to check if you haven't already --

1) Anything that is connected to the board that you want to "turn off" to eliminate it as a suspect, make sure you unplug it's power cord. I had a ground loop hum that came through the sound card of a PC which was turned off. The PC was plugged into the same circuit as the sound board, but the PC's monitor had been plugged into a different circuit. Even though the PC and monitor were turned off, I was getting a ground loop hum through the monitor's power cord, monitor-to-PC video cable, and out the audio card ... go figure! But it teaches you how pervasive these things can be.

2) If you want to take a look inside the LX7, I have an LX7-32 original series and it opens up pretty easily ... six screws allow you to open up the top with all knobs still attached (don't take off the knobs like I did :| ), and then you can check all the connectors. When I bought our board off of eBay, Aux 6 wouldn't work for the entire right bank of channels. I opened it up and reseated a couple of ribbon cables, and all was fixed Must have jiggle loose a bit during shipping. So who knows -- you might spot something, for only 10-15 minutes of careful work.