Homework for Miriam... and other new techs

[gafftaper]

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]

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]

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.

[gafftaper]

Originally Posted by charcoaldabs

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]

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]

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

[Eboy87]

Is it bad if I'm up to 23?

[derekleffew]

Originally Posted by punktech

...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]

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]

Originally Posted by gafftaper

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....