Homework for Miriam... and other new techs

gafftaper

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So Miriam you were asking about practicing things in another thread. Here's a little homework assignment to get you thinking if you are interested.

You are operating a very simple sound system with the following equipment. (Nothing particularly special about the equipment itself, it's all pretty basic gear.)

Your have two Sure SM58S microphones.

You have a Mackie 1202-VLZ3 mixer

You have a Mackie FR800 amplifier.

You have two Mackie C300z speakers.

The system is set up properly, all connections are correct, you test it, and it works. You leave the area for a while and come back before the show starts. The performer picks up the microphone and no sound comes out.

By my count there are 14 things that could possibly be wrong. Some are unlikely, but all are possible ways to get no sound out of this system.

This is one of my favorite exercises for teaching sound to new students. It's more fun to do in class with the actual equipment. I have the class turn their backs for a bit while I mess with something else then have them figure out what I "broke" this time.
 

mbenonis

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Troubleshooting is one of the most important things you will learn how to do. The mark of a good engineer is not whether he/she can run the equipment, but rather whether he/she knows what to do when things go wrong.

Random aside: The other day my lighting class TA had a troubleshooting exercise, where she broke stuff before class, and groups of three had to go up the the grid and fix what she broke. Of course, she gave my group the most problematic one. Two lights, into two circuits, connected to the same dimmer. There were three problems - (1) one bad cable, (1) missing lamp, and (1) tripped breaker (this isn't terribly common, but it could happen).

So - try to list everything that could go wrong in this system, IN ORDER of probability of that problem (i.e., the chances of the amplifier going bad are small, while the chances of the mic switch being an issue are high).
 

gafftaper

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Wait... I've now got 18 things that could be wrong... there may be more.

I also like idea of listing them in order of the most likely problem... but let's leave that for tomorrow's home work. First let's just try to figure out all the things that could be wrong. Then we can prioritize the most likely cause and finally move on to how do you figure out what's wrong.

EDIT... I'm up to 21 things that could go wrong now.
 
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gafftaper

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Psssst! How many people around the Booth do sound...? Catch my drift? ;)

Hey I admit I rarely read this board, the content is usually too equipment specific to be interesting to me. But Miriam wants to learn something so I'm venturing out with a little educational challenge.
 

punktech

Active Member
my ex-bf would be all over this one. he probably would have been constructing the "what can go wrong list" in his head before he even read the part about no sound from the mic. my personal favorite for anything that can go wrong, "it got disconnected" happened to me last year with a color scroller, luckily before everyone got too excited i was like, "lets look at the cable first, perhaps it's there, that's the easiest thing to do first, we'll go in order from easiest to figure out to hardest"
 

icewolf08

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Do we all get to play or is this for miriam only?
 

derekleffew

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...that's the easiest thing to do first, we'll go in order from easiest to figure out to hardest"
You bring up an interesting philosophical question: Once the list is compiled, even in order of probability, does one chase the most likely problem or the easiest to fix? I think I would tend to do the "easiest to fix" for the first couple, then move on to "most likely," but I'm not sure. After a while, troubleshooting becomes instinctive. Then again, there's nothing like experience, as when a more experienced technician says something like "AF1000s often have the problem of functioning fine, but not passing data, so put that one at the end of the line." This would be after I've isolated the problem by re-plugging data bypassing the unit. Sorry to interject lighting, but couldn't think of a good audio example.
 

gafftaper

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23! Dang it Eboy Now I have to think some more... it's actually quite amazing how many problems there can be with such a basic setup.

Alex give the young ones a chance to think it over first. You can play too later...
 

icewolf08

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23! Dang it Eboy Now I have to think some more... it's actually quite amazing how many problems there can be with such a basic setup.
Alex give the young ones a chance to think it over first. You can play too later...
Ok, but I am up to 26....
 

avkid

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Honestly, only in the 20s??
I can think of at least 10 about AC power alone.
 

icewolf08

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ok, well, I was keeping it simple, but tonight's performance of "Doubt" is almost over and I am up to 42.
 

gafftaper

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ok, well, I was keeping it simple, but tonight's performance of "Doubt" is almost over and I am up to 42.

42! I thought I was keeping it simple with this exercise. We'll give Miriam first shot at the answer. Then you can dazzle us with your list.
 

icewolf08

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Then do we get to vote on best answer?
 

Hughesie

Well-Known Member
im up to 42
including
desk disconnected from power
actor speaking into wrong end of mic

just some funny examples that entered my head..
 

len

Well-Known Member
Does "performer yelling into speaker thinking it's a really big mic" count?

BTW, did you know you could use a mic as a headphone in a pinch? I just learned that the other week.
 

miriam

Active Member
Wow!
Thank you so much for the excercise. If nobody minds, I will try to aim for 14 not 53.
Okay, so.
The mic could be turned off.
the mic could have come loose from the cable.
The mic could have been switched to a different mic by someone else, and the new one is broken
maybe something sharp or heavy got dropped on the cable, damaging it. (Is this likely?)
These could have happened to either mic.
Do we have a multicable? If so, then maybe someone switched where the mics are plugged in, and the correct channels for the mics are off.
or someone plugged the wrong numbers into the mixer channels. This one could happen even without a multicable.
Or someone unplugged one of the mics and did not replug it all the way.
Someone could have hit mute.
or tripped over the cord and unplugged the mixer.
or turned off the gain.
or the master could be off.
or the fader(s) could be off.
We didn't learn about eq yet, so I don't know how that would affect it.
the lines to the amplifier could be loose.
or maybe the amplifier is off.
Or maybe the speaker cables are not turned all the way.
We just started about amplifiers, so I don't yet know what else could go wrong there. Unless someone poured a bunch of water into it.
The end of the cable in the speaker itself may not be turned all the way.
The cable could be plugged in for a speaker configuration that I'm not using. (would this produce no sound at all?)
Okay. That's what I can think of right now. How did I do?
 

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