# What is wrong with this pic - Number IV



## Mayhem (Dec 26, 2004)

I hope that everyone had a good holiday and that your minds are nice a clear. Now, the following picture was taken when I was asked to service an Amplifier. Now this is a home amp, not a professional PA one. However, I have seen a few professional ones in a similar condition.




Here are the things that I would like you to consider:

What is the problem?
What can this problem cause? and how
What can be done to prevent the problem?

Think about the amps that your school/theatre/church have and where they are located.


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## avkid (Dec 26, 2004)

that looks to be covered in pet hair and dust , to stop the problem:cover when not in use and clean occasionally!


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## soundman (Dec 26, 2004)

I secound dust and would suggest puting a filter infront of the intake fan/grate. Also might consider moving the amps from the bottom rack space to a bit higher because then they wont suck in so much crud of the ground.


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## great_beyond (Dec 26, 2004)

the problem is that dust has covered everything, causing:
- insulate everything and over heat it (fire)
- buildup a static charge and destroy the circuits (fire)

First thing would be to clean everything, then to prevent it, place a couple pieces of cheescloth over the intake fan, and other holes for ventalation, and cover when not in use,


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## ccfan213 (Dec 26, 2004)

it looks to me like dust or possibly sawdust, i had a similar issue in my house where my dad started building computers in the workshop in our basement, naturallly there is sawdust everywhere and it screws up electronics and is very flammable. first off you should not keep an amp in a room where there is sawdust, but other than that i agree with what other people have posted about covering and putting screens in vents


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## zac850 (Dec 26, 2004)

It looks like sawdust that is covering it. This is bad because things can short out, destroying the amp and possibly causing a fire.


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## Mayhem (Dec 26, 2004)

Ok - everyone is right in so far that the circuit boards are covered with dust. However, dust in itself is not conductive. 

great_beyond is heading down the right track with the potential problems that dust can cause but there is a bit more to it.

avkid - as for cleaning the amp, how often is occasionally?


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## soundman (Dec 26, 2004)

your right its more like an insulater which can cause a problem to with heat. Also it can gum up fan bearings cause them to fail which is not good. Depending on where the amps are used I would clean quaterly if not more. Taking it out of the rack opening it up and blowing it out w/ air dosnt take that long.


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## Peter (Dec 27, 2004)

I really really hope the strands of stuff in there is not asbestos! Probably abit less likely to be found in a house, but people with racks in other buildings might have to keep an eye out for it abit more. 

asbestos is BAD news, it's harmless when it's not in the air, but it has a tendency to become airborne and get stuck in people's lungs and cause VERY serious medical problems. 

It is really a fairly wild guess, but hey, cant hurt to toss it out there can it? 

(JBTW, I will be gone out of town for a week, and i hope to see lots of posts here by the time i get back! See ya all later!)


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## Mayhem (Dec 27, 2004)

Nope - not asbestos. The fibres are actually spider webs.

Now we are getting off track here. The composition of the dust is not important. All you need to know is that it is dust. Now, think about what problems dust on electrical circuit boards can cause.


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## Ex-Techie (Dec 27, 2004)

Besides being an insulator which increase operating temps, dust can also be a conductor which can cause both hard and intermittent shorts, e.g. failures and or noise in sound gear. Moreover, contaminates combined with moisture can become corrosive. Note, this is much bigger problem with newer state of the art electronics versus older through-hole technologies. The new chips have much tighter lead to lead spacing (pitch) and the possibility of shorts is greater.


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## Radman (Dec 28, 2004)

I see the problem:

Made in Japan!

No I'm kidding....


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## Mayhem (Dec 28, 2004)

Ok – well Ex-Techie has started to link things together. Dust, whilst being an insulator can cause overheating through holding heat close to the components, it is not conductive when dry. 

However, add a little moisture to the equation and you do have a very nice conductive medium. Now we all know that liquids and electronic components do not mix, nothing new here but most just think that by preventing people drinking near, or placing a drink in the immediate vicinity is enough to remove this risk.

This is not the case. Part of this question was to get you to link the whole dust + moisture = risk scenario as being a serious problem. When stating that you should think about your own theatre environment, I wanted you to think about the possible sources of moisture. 

Another thing was to get you thinking about equipment maintenance (and why it is important). There was some discussion about covering air vents but I would not tend to do this. Keep in mind that some amps have fans that force air into the amp, some have fans that draw air out of the amp and some have both.

Now, I am not actually going to elaborate on these points now. Rather, I am going to leave them open for discussion. Part of being a responsible tech is being able to look at an issue and then identify what the possible problems that can arise and why. Once you start thinking in this way, you will find that risk reduction becomes much simpler. Remember, you are much better asking “would this cause a problem” than asking “Gee, I wonder why that happened”. Initially though, looking at past problems will put the little red flags into your mind, which (hopefully) will pop up when you see similar things later on.

So – the challenge is still there – cite the possible sources of moisture that are commonly seen in the industry and give the basics of cleaning amps and keeping them clean.

I look forward to reading the discussions.


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## soundman (Dec 29, 2004)

Beer, water and summer gigs where it is 110% hummidity and will rain if just given a chance. Most amp racks either are used to support the moniter desk or have NO DRINKS wrote on them using gaff tape.


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## mbenonis (Dec 29, 2004)

One possible source of moisture would be improper HVAC settings for the room/facility. It could also be caused by leaving doors open (expecially in a humid climate) if the rack is near an exterior door. Solution: make sure all doors stay shut and that the building is kept relatively dry.


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## ccfan213 (Dec 29, 2004)

you can install a dehumidifier in the room where you have your amps, and of course keep liquids away from it. also put the amps high in the rack so if there is flooding or a spill of some kind they are less likely to get wet.


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## JahJahwarrior (Dec 29, 2004)

thinking of our amps and dimmer packs...and man, i actually thought that dust would hold in moisture and was so excited and then i read mayhems' post......drat. oh well! 

causes of moisture: i live in florida and we had many hurricanes this year. 
outdoor gigs, or an amp that is kept outdoors, tha would be a very fine candiate for dew from moisture! also, if you have an amp in a cold room, then turn the heat on, you will get some condensation inside. you have to keep that in mind in the winter. drinks are always a problem but you konw when that gets in there, it's the moisture in the air that you can't tell about. how to protect: 1) keep your amps in a dry place, up in the air, i mean in a well ventilated spot, where ther eis lots of air around it. 2) in the winter, keep the heat on so the amp doesn't get freezing cold, set it for like 60 or so. and don't warm it up to toasty warm too fast. 3) in the summer don't let it get really hot then stick it in the ac really fast. don't ever leave amps in hot sun. (I'm thinking more portable amps or racks here) 4) if your room gets really wet, say you have a leak in the cieling and the humidity is super thick, buy a dehumidifier and run it for a while, close to your amp.


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## thelightguy (Jan 5, 2005)

It is helpful to have a fehumidifyer in the room, as this not only eliminates moisture, but mold.


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## Mayhem (Jan 9, 2005)

Ok - we seem to be a little stuck on this one.

So far we have correctly identified the thick layer of dust as being a problem for the following reasons:
 insulator – reduces the heat exchange which can lead to damaged components
 fire hazard – a large amount of dust could catch on fire, sparking a larger fire once other combustible materials catch alight.
 Shorting – once the dust becomes moist, it can conduct electricity, leading to shorts and arcing between tracks and components.

You have also recommended cleaning your amps and covering them up.

This is all good work. However, there is one very common cause (the most common) of moisture in the entertainment industry that has not yet been identified. I’ll give you a hint:

*It is something that many of you use and several post have been made on this site regarding their use. When combined with dust, the end product is a nice sticky moist conductive medium.*

The other thing that I would like to see explored in a bit more detail is the process of cleaning an amplifier. Who can give me a basic step-by-step breakdown of what to do. Just a few lines on each point is all I need. Something similar to the dot points I used above.


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## soundman (Jan 9, 2005)

aghh fog/haze


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## Mayhem (Jan 16, 2005)

Mayhem said:


> The other thing that I would like to see explored in a bit more detail is the process of cleaning an amplifier. Who can give me a basic step-by-step breakdown of what to do. Just a few lines on each point is all I need. Something similar to the dot points I used above.



*ANYONE?*


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## avkid (Jan 16, 2005)

fog juice,duct tape?


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## Mayhem (Jan 16, 2005)

Oops - forgot to say Correct to the Soundman's identification of smoke and haze particles causing potential shorting problems when combined with dust in electrical environments. Remember, this is not just an issue for amplifiers but for ALL electrical equipment including lights and dimmers.

Not sure how duct tape would get into a fixture and mix with the dust but nothing would surprise me in some places that I have worked. 

So well done to Soundman and avkid for picking up on smoke and haze as sources of moisture in an electrical environment.

Now – how do we go about keeping amps (for this example) clean and in good working conditions?


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## soundman (Jan 16, 2005)

Heres a qucik little guide;
1. one clear workspace. I have an old white towel I use when I take apart things, the white shows little screws and springs better and prevents them from rolling. 
2. ground yourself. Those little $2 wriststaps can save your $200 doller amp. If you dont have one touch the metal case while the amp is still pluged in and avoid shuffling your feet on carpet
3.Open it up. If need be write down where screws go and any wires you need to unplug go.
4. Gett the dust/crud out. If it looks like a fur ball in there a pass or two with a vacum might not be a bad idea, then to get the rest of it out blow it out with compressed air, try to avoid high power compress air because that could probly wont but could strss a joint or shoot a piece of dirt into some where it shouldn't be. 
5. Put back together. Throw away any extra pieces and write your name and date on a piece of tape and stick it on the amp. That way your boss knows who screwed up or that the amp was cleaned last week and dosn't need to be done agian.


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## Mayhem (Jan 16, 2005)

Good work Soundman.

Just be careful if you leave the amp plugged in that the recepticle is switched off. No matter how experienced you are, you don't really want to be poking around in an amp that has power flowing to it.

Before I comment on other aspects, does anyone else have anything to add or discuss?


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## cutlunch (Jan 17, 2005)

Now everyone is getting all excited about cleaning their amplifiers just a reminder about *SAFETY!!!* 

As you all know the amplifiers connect to the electricy supply so everyone remembers to unplug them from the wall.

But unless you know about how the inside of an amplifier works you may not be aware of the electrical hazard that maybe present even when the amplifier is unplugged.

The power supplies in the sort of amplifers we use in theatre use quite high voltages. Between the positive and negative supply rails the voltage can easily reach 100 volts which can give you a nasty shock and in some cases maybe fatal if you come in contact with it. Also if you accidently short circuit the supply with other parts of the amplfier by accidently touching it with things like a screwdriver, the metal part of a vacum hose etc you may literaly blow parts of your amplifier to Kingdom Come. Transistors may melt, printed circuit board tracks may lift which definetly means a servicemans bill and a please explain from the principal.

Because the amplifier needs large amounts of electrical energy quickly to reproduce loud pieces in the music there are a number of large capacitors to store this energy. And because they store it, when you have turned off the power these high voltages will remain for quite some time. So never turn an amplifier off straight away and start working inside. Leave it for a couple of hours to bleed off the energy. If you are comptent with using a multimeter you can use that to check the power supply voltage has gone to zero.

Some people will have diffrent ideas on the length of time that it will take for the energy to drain away. This is just a general guide so feel free to offer suggestions on the length of time you find necessary. Obviously different amplifiers will become safe at different rates.

To be honest only people who really know what they are doing should ever open an amplifier as there is too much chance of doing more harm then good.

Also things to remember if you take the lid of your amplifier are:
It may be against school policy and drop you in it.
It may void the warranty on gear.

The best thing is to try and get your school to send all the gear to a qualified serviceman once a year for a clean and check.


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## soundman (Jan 17, 2005)

When working with my computer supplie I turn it off unplug it then turn it back on, that spins the fans for a secound or two and I would assume empty out the capacitors. Silly me to forget theat


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## Mayhem (Jan 20, 2005)

After being overwhelmed by the response on the basic steps to service an amplifier, here are my thoughts on the topic. 

cutlunch raised some good points about safety and I want to reinforce that statement. The aim of this topic was not to turn you all into little amplifier, dimmer, sound board, lighting board, moving light etc service technicians, nor was it to have you attack such equipment in your school or theatre. The aim was to get you to think about the problems that dusty equipment can cause. I used an amplifier as an example, purely because I did take some pics of one that came through my workshop. It could have just as easily been a dimmer.

Once you had thought of the complications of having ‘dirty’ gear, I wanted you to then think about what common causes of moisture could be found in the theatre environment that could really cause some problems with the circuit boards that are now not only dusty but moist as well. It took a while and some prompting to come to the conclusion that:

_dust + (smoke/haze fluid or humidity) = bad news_

Given that we now knew the reasons to keep equipment clean, I was looking for a quick rundown on how to do this. Soundman made a very good start but no one really took up the challenge to add to this. cutlunch raised the safety issues and I have held off responding to these posts to see if anyone else wanted to add anything. However, I feel that the time has come for me to respond with my method. Now this is not to say that mine is right or wrong or any better than the next person. Although, I do hope that it stimulates some additional discussion.

In his post, cutlunch made comment about the capacitors that are used to store energy to ensure that the lower frequency sounds do not draw too much on the mains power. They essentially act as a reservoir. Some people that I know discharge the caps before servicing an amplifier and if you are measuring the ESR of a capacitor, they need to be fully discharged anyway. I use a discharge probe for this purpose.

I would be much more concerned with people leaving the power plugged in (although soundman did clarify this point this is a caution to other people) . 

The steps that I would use are:

1. Visual inspection of all external connectors, plugs, switches, pots etc
2. Discharge capacitors
3. Dust with a vacuum cleaner and small brush (I have an attachment for a vacuum cleaner that has brush nozzles and other attachments that are about ½” in diameter)
4. Using low pressure compressed air, blow out any areas that cannot be accessed during step 3
5. Inspect fans for broken blades or resistance to turning (do not 'spin up' using compressed air as it can damage the fans) and clean the blades
6. Inspect components, boards and wire for any physical faults (such as dry joints, discoloured heat transfer compound etc) and repair/replace as necessary
7. If necessary, clean circuit boards with a circuit board cleaner
8. Clean and lubricate switches and pots
9. Ensure that any wires or connectors removed are replaced and in the correct position and that any internal fuses are secure in their holders.
10. Replace cover and test.

I power up for the first time using a variac and a clamp meter (to check for any shorts) and then run the amplifier up on a dummy load with a signal generator and check the wave forms on a CRO but I doubt that many of you will have these resources.

Some people initially suggested covering up amplifiers and/or placing materials in front of fans. This is fine for equipment that is not in use, but please do not do this if it is in use. First off, you will be reducing the ability of the equipment to dissipate heat, which can lead to component failure. Secondly, you will restrict air movement through the fans. Remember, some equipment use fans that suck air into it, some use fans that blow air out of it and some use both. Some manufactures actually do place filters on their fans and this is ok because they have calculated this into their design.

Once again, I am not advocating that you run out and pull the covers off of your school equipment. My aim is to ensure that you understand the value of regular servicing and the potential hazards of simple things like dust accumulation on circuit boards.


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## MOONLIGHTING (Jan 26, 2005)

Great stuff.
In many cases the filters can be removed and cleaned in warm soapy water. Sometimes they are too sticky to clean with a vacuum. Must be completely dried before installing again, of course. Or you could just replace them with the same kind....
Mike


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## Mayhem (Jan 26, 2005)

Thanks Mike - good point.


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