Troubleshooting Equipment Problems By: Keith Ling

April 8, 2008 by Mobile Beat Staff Writer

Remain Calm!!! This is one of the best pieces of advice that I can give you. Let me explain what the “Big Eye” is. This phenomenon occurs, when something such as a major equipment problem arises five minutes prior to having to introduce a wedding party. Your two eyes will instantly mold together into one, creating tunnel vision. This is known as the Big Eye, and you should avoid this at all costs! Losing your cool when an equipment problem arises will drastically reduce your chances of correcting the problem. Remaining calm, cool and collective will help you find the problem much quicker.
Do not tell anyone about the problem unless it is absolutely necessary!! This will limit the amount of bad publicity you get from an equipment problem.
Use the process of elimination to find the problem. Simply put, switch things that work with things that do not work in order to trace the problem down to the point of origin.
Keep in mind, if you are using professional grade equipment, the chance of a speaker or the amp “blowing” are very minimal!!! In our experience, the most likely causes of most equipment problems, are faulty interconnect cables, and human error. If you keep this in mind when a problem occurs, you will be able to relax, and diagnose the problem with less difficulty.
The use of quality interconnect cables, speaker cables and extension cords cannot be emphasized enough. If you have good quality cables that are brand new, you have a baseline with which to work. Typically, once you have tested a new cable of sufficient quality as being in good working condition, it doesn’t just “break” overnight. When something doesn’t work, and you KNOW that your cables are in good condition, it will reduce the possibility of the problem coming from your cables.
Use a standard system to identify a faulty connector cable or cord. I recommend that you tie a knot in both ends of the cord you have identified as being bad, so that it does not get confused as being a spare in the future.
Always keep all of your connections in line, keeping the left channel output from your music sources connected to the left “in” and “outputs” of every components, all the way down to your speaker. The same goes with the right side. This way, if the left speaker isn’t working, you will be able to trace the source of the problem much easier.
Scenario # 1
No Electrical Power To All Components When Initially Turning Power OnYou’ve set your system up completely, switched on your power distributor and your equipment is not turning on – none of it. Your first step should be to check your power strip light to see if the power strip is on. If not, then check the outlet that you are plugged into.

Before unplugging, make sure your entire system is turned off. Unplug your extension cord and examine the prongs. If it appears OK, plug it back in and turn your system back on. Make sure the levels on your mixer and amp are all at minimum! Unplug again and try plugging in an extra power strip. Flip the switch on and see if it lights up. If not, you probably have a dead outlet or a circuit breaker has tripped. Before assuming that the outlet itself is dead, plug an appliance directly into the outlet, such as a CD player.

If you still have no power, it’s a good idea to approach someone at the hall about your problem. Some outlets are controlled by switches. Some outlets have a tripped circuit breaker, which they can often access and flip back on. Believe it or not, some banquet halls turn the power off to all of the wall outlets because they believe that they are conserving energy! In this case, all you need to do is turn the breaker on at the panel.

Of course, the outlet may simply be dead and you’ll need to find the closest working outlet. If you suspect the circuit breaker, find a gray metal box mounted in the wall. You will see a number of switches. Most will be in the “on” position. If you see one in the “tripped” position (in the middle), flip it first to the “off’ position, and then to the on position. This may be your circuit! Go check with the power strip!

Now let’s assume your outlet is working. Your extension cord may be at fault. Try another cord. Hopefully, you have a backup. If not, ask if you can borrow one. You should always have at least two extension cords in case one is faulty. Make sure the cord is plugged in properly at the wall and where it connects at your equipment.

I once followed all these procedures and still couldn’t get power to my equipment. I started to panic, but then I went back and followed the current trail back to my power strip. I had forgotten to switch it on! Usually these problems are very simple. Learn to laugh at yourself when you do something this dumb. It helps your smile when the show starts.

Scenario # 2
Power Failure To All Components While Playing Music

The dance floor is rockin’, you’re taking a request and all of a sudden…. WHAT???!!! There is no sound and no juice to your equipment. Your first glance should be at the wall outlet that you are plugged into. Make sure it hasn’t been pulled out. Whenever possible, plug in your system where no one else can reach it. This happened to me at an Elementary school once. The outlet was only about 2 inches from the floor. It was also beside the table where I had my request pad. When I announced I was taking requests, a crowd developed and my extension cord was knocked out. This happened three times before I finally had to place my hand truck where the kids couldn’t touch the cord.

Also, make sure the other end of the extension cord is plugged in. You may have just tripped on it. The next thing that you should check, is the power light on the power strip. Is the light lit, indicating that you have power up to that point? If those two are fine, you have probably tripped a circuit breaker.

If you are running two amplifiers or some power hungry lights, you may have to back something off. The important point to emphasize here is that you can’t go back to what you were doing because you will most likely trip the breaker again.

In a typical electrical system, there are usually six to eight outlets on a circuit, which is tied to one circuit breaker in the electrical panel. Ideally, you should be plugging your sound equipment into one circuit, and your lighting equipment into another circuit. The problem is figuring out which outlets go to which circuit breakers. Most DJs that use a modest lighting system (a few par cans and a beam style light) do not go to the trouble of locating a separate circuit. If this is the case, and a circuit breaker trips, the lighting is most likely the source of the problem. Lighting draws a tremendous amount of electrical power and you should try to run the extension cord to an outlet as far away from the original outlet that you started with. You should try to plug into an outlet that is on a different circuit. One possible solution is to take the extension cord that is servicing your lights, and start plugging it into other outlets PRIOR to turning the breaker back on. Once you find a “live” outlet, leave the lights plugged to that, and turn the breaker back on to the sound equipment. This may not be possible, if the event requires you to turn the power back on IMMEDIATELY (I.E., a wedding). In this event, you will need to disconnect the lights. Obviously, your lights are not a priority if you continue to trip the breaker.

Check to see if there are halogen lights, coffeemakers, or other electric cooking appliances plugged into the same circuit. I once played a homecoming dance where 5 halogen work lamps were shined on the walls. I was running a bi-amped system, and used a Vertigo II, and a halogen spot on my mirror ball. Did I mention my fog machine as well? The halogen work lamps were pulling about 1.5 amps each. I tripped the breaker three times before suggesting to my contact to turn off the work lamps. That did the trick, and we were rockin’ the rest of the night!

On yet another occasion, a caterer had a lot of heating appliances plugged into the same circuit that I was operating on. My sound equipment drew just enough electricity to trip the breaker. You may have to plug into a different circuit, or suggest other items be plugged in elsewhere.

Before going to the circuit breaker box, TURN YOUR ENTIRE SYSTEM OFF! You do not want to suddenly turn power back on when your system is cranked. You could blow you amp, speakers, or at least some fuses. Find your breaker box and proceed as in scenario #1.

Scenario # 3
One Component Only Is Not Receiving Power

You have power to all of your components except one. Make sure the power switch on that component is on. I amaze myself at how many times I forget to do this. If that doesn’t work, check the plug and make sure it is properly plugged into you power strip. Check the prongs to make sure they are not bent. Try another “outlet” in the strip if possible. Believe it or not, I have actually had one outlet on a power strip go bad!

Check the fuse to the appliance, if it has one. Most amp’s and some mixers and CD players have fuses, and this is one potential source for a component to not operate..

Most professional amplifiers have two features that other components do not. The amplifier may have an automatic internal “shut-down” device (similar to a circuit breaker) built inside that will shut the amp down if it is driven too hard. When this happens, the power light will not be lit, and it will appear that the amplifier has no electrical power. This very same symptom can occur if the fuse to the amp has blown. The only way to tell the difference is to check the fuse to the amp. If the fuse is fine, you can assume that the shutdown device has activated. The only way to fix the problem when the shutdown device has activated is to cool the amp as quickly as possible. Once the amp turns back on, you must lower the volume on the mixer, since the main reason that the shut-down device activates is that you played distortion!! This typically happens when a newer DJ is using a smaller amplifier for a large event, and tries to get more out of the system than it is capable of delivering.

The amplifier may also have an external breaker button that may activate. In some brands, this breaker has taken the place of the fuse. If your amp has this feature, you should become familiar with its location and normal operating position. This way, you will be able to easily identify as to whether it has tripped. As with the internal shut down device described above, if the external breaker button trips, you cannot go back to playing at the same levels you were prior to it’s activation! Remember, it activated for a reason! This leads me to my next subject, playing distortion.

Most DJ’s assume that the possibility of blowing a speaker comes from playing too loud. This is definitely not the case. Professional equipment will tolerate loud volumes of music for hours on end. The thing that blows speakers is called distortion. This occurs when increase the levels on the mixer from a crystal clear sound to a slightly distorted sound. It is easy to blow a speaker rated at 500 watts with an amp rated at just 50 watts if you pump a distorted sound into the amplifier and speakers.

The key is, keep the sound crystal clear at all times. Good indicators on when you are playing distortion are your VU meters on the mixing board. If you are constantly in the red, you will probably be playing distortion. If you are unsure, walk around to the front of the speakers and check the sound. When in doubt, lower the level on the mixer. Playing distortion will most likely blow the horns/tweeters on the speaker first.

If this all fails, you may have a bad power cord or power supply in your component. This is a great reason for having backups with you, especially if the component is a mixer or amp.

Scenario # 4
One Speaker Does Not Work/One Channel Is Out

The two most likely causes of this problem are:

Faulty interconnect cables
A short on a terminal output post on the mixer, EQ, CD player, etc.
I have already described the importance of having quality interconnect cables that are in new condition. Let me elaborate on the problem with a terminal on a player, signal processor or mixer shorting out. Plugging and unplugging interconnect cables takes its toll on your mixer, signal processor and CD/Tape players. Each time you plug and unplug, it places wear and tear on the unit. Each terminal that you see on the outside of a component has a wire soldered to it on the inside. Eventually, this solder joint gives way, and you begin to have a short in that terminal. At first, you can gently wiggle the terminal, and get the sound to “pop” back in, however eventually the connection inside will be totally lost and you will have to repair the unit. Placing your equipment in a case and leaving everything pre-connected can easily avert this problem.

Your initial actions for sound to one speaker only

While the music is playing, observe your VU meters. Make sure your mixer is in stereo mode. If only one channel is registering a signal, then the problem is occurring before or inside the mixer. If both channels are registering, then the problem is occurring somewhere between the inside of your mixer and your speakers (it is possible to have the VU meters show a stereo output, and the solder joint at the output terminal be bad).

The first thing you should do in this situation is to play a different CD player. This will help you determine if you have a problem with the entire system, or just one part of it. Does your other CD player or tape deck produce sound to both channels, or is one channel also dead? Lets break down the symptoms so you can follow the sequence of events easier;

One component produces sound to one speaker only, all others work fine in both channels.
If you have one particular CD player that is only producing sound output to one channel, but all others are working properly, you may safely assume that the problem is located in one of these three places: 1) in the source component itself (i.e., bad playback head on a cassette deck, or defective stylus on a turntable); 2) in the connection from the source component to the mixer; or 3) in the mixer input itself.

Check your cable connections from the music source (CD player, turntable, mini-disc, etc). Re-connect both ends of the audio cable, gently wiggling the effected terminal (left or right channel) on the mixer and the CD player or other playback device. The problem could simply be a short on one of the terminals. If the problem persists, try switching the right and left cables at the mixer. If the problem persists, you have a faulty RCA cable or audio source component. Replace the cable first, before assuming the worst. Cable failure is the most common problem encountered by sound engineers.

Try plugging the CD player that is only producing one channel to another input on the mixer. This will tell you if the player itself is bad, or the problem is located inside that one input on the mixer. Mixer inputs do, occasionally go bad, and you shouldn’t assume that just because you have changed the connector cable without success, that the player itself has a short inside the unit.

Sound From ALL Playback Devices Going To One Speaker Only
The mixer VU Meters may be showing a stereo output, but do not assume that the mixer is actually sending sound out of its output connections! One easy way to rule out your speaker, or speaker cable, is to plug the speaker cable that isn’t working, to the side of the amp that you know is working. If by doing this, that speaker starts working, you have ruled out the possibility of the speaker and speaker cable as being bad. This means that the problem is somewhere between your mixer and amp.

However, if you switch the speaker cable to the other channel on the amp, and it still does NOT work, this means that the problem is in the speaker cable or the speaker itself. Go to your speakers and check that connection. Try replacing the speaker cable. If not, perhaps the speaker is blown.

If you have ruled out the possibility of the problem being the speaker or the speaker cable, work your way back to where they connect to the amplifier. Check that connection carefully, especially if you are using banana plugs. Check your amplifier settings. Are both channels turned up? Check the inputs to your amp. Again, a loose connection could be the culprit. Follow your connections all the way back to your mixer. If you are still encountering a bad channel, try reversing the connections ONE AT A TIME. When the bad channel changes sides, you have found your bad connection. Replace that cable immediately.

Occasionally, a mixer can be the culprit, sometimes even when the VU meters show a stereo output to both channels. If you have traced the problem to the inside of the mixer, try plugging to one of the other outputs on the mixer, such as a “tape out”. If this doesn’t work, if your mixer has a mono mode, activate the mono mode and ride it out that way for the evening. One word of caution! It is not preferable to plug both speakers to one channel on the amp, when the mixer is only producing one channel. This makes your amp work much harder. If your mixer doesn’t have a mono mode, carry spare “Y” adapters so that you can take the one channel output and drive both channels of your amp.

It is possible, but rare, that your amp could lose one channel. In this case, plug both speaker cables to the one channel on the amp that is working. Note: You should only plug both speakers to one channel on the amp after you have correctly diagnosed that one channel on the amp is bad! In my experience, when a DJ tells me that they plugged both speakers to one channel on the amp, they incorrectly diagnosed the problem, and put the “quick fix” on the problem.

Scenario #5
No Sound Coming From One Component In Either Channel, All Others Have Sound To Both Channels.

This is probably a very simple problem. For example- my CD player is plugged into the “line” input on Channel 1. Is my selector switch set to receive signals from the phono input or the line input? OOOPS! Boy did I feel stupid! But that sure was easier than replacing my cable.

Rats- that didn’t work! It is highly unlikely that the connector cable is bad on both channels, but try replacing the cable. If that still doesn’t work, you have either a defective source component or one input on your mixer is defective. If you have a spare input on your mixer, try it. This may solve that problem. Otherwise, you will need to replace or repair your source component.

Scenario # 6
The System Doesn’t Sound Good

Scratchy sound can have several sources. If you are playing records, your stylus may be extra dirty or even damaged. Your record may be damaged as well. If you are playing cassette tapes, the heads may be dirty. Clean them with a professional head cleaner using soft tip cotton swabs. The heads may also need to be demagnetized with a head demagnetizer. CDs generally do not sound any worse unless there is a serious problem with the digital converter.

The most common problem encountered with CDs is skipping. This may occur if people are bumping your equipment or the floor. Try using isolation pads under your case to minimize this problem. CDs may also skip if they are dirty or scratched. Check the CD and clean if necessary. A third reason for a CD player skipping is a dirty laser lens. Keep a CD lens cleaner handy. If you start to have skipping problems, this may help eliminate them. Make sure your CDs are free from moisture as well as dust.

Another frequent source of substandard sound system occurs when the equalizer is accidentally deactivated. I have had this happen more than once!

If you’re getting a really distorted sound, make sure that your CD player isn’t accidentally plugged into a phono input. You would be amazed at the number of people that have made that mistake, and you only make that mistake once!

If your mixer has a stereo/mono button, it will not sound quite right, if the button is placed in the mono mode. This isn’t to say that playing in the mono mode is a bad thing, as a stereo sound can only be appreciated within approximately 25 to 35 feet of the speakers. After that, people really can’t tell the difference. However, if you are used to playing in the stereo mode, and the system doesn’t sound the way you are accustomed to hearing, this could be the problem.

My number one cause of “bad sound” comes from inadvertently flipping my microphone switch in the “talkover” position. This causes your sound level to drop dramatically. The reflex is to turn up your source fader and then your master volume to compensate. If this happens to you, TURN YOUR FADERS DOWN BEFORE FLIPPING THE SWITCH BACK!

Mixers are the single most common source of noise in the DJ system. They collect a lot of dust that settles into the fader slots. The dust both interrupts the electrical contact and generates static interference in your signal. It is best to clean your mixer with a slightly damp towel and then dry thoroughly. You can purchase cans of “blast air” at computer stores for cleaning your fader slots. The scratchy sound generated by a bad or dirty fader is the best argument for keeping your mixer in a sealed case when not in use.

If you suspect a particular fader is the source of your noise, try using another channel if possible until the fader can be replaced or fixed.

Quality power amplifiers usually do not generate a lot of noise unless they are being fed an excessive or dirty signal. Static is a frequent noise related problem. This occurs when something isn’t grounded properly, or when a “ground loop” occurs. The ground loop can be avoided by using insulators with your rack screws on everything that you rack mount, from your mixer, to your EQ or signal processor, down to your amp. If the insulators do not fix the problem, perhaps a signal processor or EQ is too close to your mixer or amp. Try isolating all of your components, one at a time to see where the problem is coming from. I know more than one DJ who has had to reconfigure their case system to reduce static.

For other types of noise or bad sound, check your mixer settings and your VU meter. If you are going into the red too often, your source component fader is set too high. Also, beware of setting your master volume too high or too low. If you are using banana plug outputs, make sure there are no stray strands of wire touching the opposite channel or polarity (I.E., black wire touching red).

If your noise is intermittent, it may be a connection. Check your cables, inputs, and outputs. Cable shorts are the single most common source of signal dropout. If your inputs/outputs appear dirty, clean them with a professional electrical contact cleaner.

The noise source we all dread are defective speakers. The problem may be with your input, and can often be fixed with simple tools. If the problem is the speaker itself, you would be best advised to have it repaired by a professional. Replacing speaker coils, foam rounds, and cones are tedious work. If you’re looking for a challenge, this is it. If only one speaker is damaged, you may simply disconnect the bad one, turn down your amp’s output on the bad one, and switch your mixer to “mono” instead of stereo. You will have to push your remaining speaker twice as hard to maintain volume, but it’s better than shutting down completely.

Scenario # 7
The System Doesn’t Play As Loud As Normal

First of all, check your fader settings. Make sure you have turned up the proper fader. Second, check your master fader. Look at your VU meters. Are you getting a signal on both channels? If not, check your signal source and cables. If so, check your microphone talkover switch. The talkover switch is the second most frequent cause of lack of volume, with the master control being improperly set as being the primary source. If the talkover switch is on, make sure your fader levels are in the normal range before flipping it back.

I hate to admit this, but I have seen DJ’s who have plugged the connector cable from the mixer to an OUTPUT on the amp. This sometimes leads to a slight sound coming out of the speakers. Closely related, would be to have the speaker cables plugged into the INPUTS of the amp!!!!!! Can you believe that someone would do this?? I have personally witnessed this!

Volume deficiency may also occur when the equalizer is deactivated accidentally. The sound will be fairly loud, but it won’t have quite the punch that it normally does. This happens on a fairly regular basis, and is one of the primary reasons that I strongly recommend that your sound check BEGINS with a check of all mixer and signal processing controls to ensure that they are properly set.

Check your amp output settings. Is the sound coming from one speaker only? If so, this will prevent your system from playing as loud as you are used to. See the section above for troubleshooting sound to one speaker only.

Scenario # 8
Feedback From The Microphone

A howling or high-pitched squeaking sound is created when your microphone is receiving music or your voice coming from the speakers. Never stand directly in front of a speaker with your microphone turned on. Try to stand off to the side and even behind the sound field whenever possible. There are several ways to immediately reduce feedback. The first is to turn down the fader controlling the volume to the microphone. The second is to turn down the master volume, only if it somehow was placed higher than normal. The third is to adjust your equalization. Howling feedback can be tweaked by reducing frequencies in the 250-1000 Hz range. This is why it is advantageous to have separate bass and treble controls for your microphone. You can make the adjustments to the mic, without effecting the sound to the music. Simply reducing the treble will eliminate much of the feedback. Squealing is usually indicative of being too close to the speaker.

When you give up the microphone to someone else, be sure to tell them to hold it no further than four inches from their mouth and stress the importance that they stand clear of the speakers. If they speak clearly and in a normal tone of voice, you should be able to provide sufficient volume without feedback. If you have a wireless mic, remember to keep the receiver level at a reasonable level. If it is too low, your signal will be weak, which will force you to turn up the other volumes. If it is too high, you will encounter howling.

Speaker placement is crucial in avoiding feedback. If you can turn the sound field slightly away from the microphone, you can reduce feedback without lowering your volume settings. Experiment with your speaker placement to minimize feedback. Try it before your show. You’ll feel more comfortable during announcements.

Always use a quality microphone with a cardoid or hyper cardoid pattern. These microphones pick up speaking voices very well, and tend to reject sound not directed into them. Make sure it is a low impedance model (with XLR connectors). I highly recommend the industry standard, the Shure SM-58. This microphone has been around a long time, and is perfect for announcements.

Mobile Beat Staff Writer (375 Posts)

This is the general editors account for Mobile Beat Magazine and Website. Who reads Mobile Beat online and in print and attends Mobile Beat events? DJs, VJs and KJs to start with, especially those who own and operate mobile entertainment services. They provide music, video, lighting and a myriad other entertainment choices for corporate events, wedding receptions, dances and innumerable other gatherings.

Filed Under: Sound Engineering for Mobile DJs