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Author Topic: Bizarre wiring on install  (Read 14199 times)

Bradford "BJ" James

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Bizarre wiring on install
« on: May 16, 2009, 10:38:42 am »

I go to a site yesterday to check why they are having trouble with a paging system. Large manufacturing plant. Powered by a single 100 watt radio shack amp.

But here's the thing, I assumed the system was run as a 70v system, but when I looked at the rear connections, there was a speaker wire plugged into the 4 ohm terminal and common. But there was also a 4 wire small gauge (looked like phone cable) plugged into the 8 and 16 ohm terminals with the 2 others going to the common.
Makes me think they were trying to have 3 pairs of speaker lines running to different locations. And nothing hooked up to 70V. All the amp had for terminals was: common, 4, 8, 16, 70V

There are horns all over the plant, and the ones that I could actually hear had a bad buzz - which is the customers complaint.
I have never seem an amp wired like that. Is there any way possible that it is correct? It seemed stupid, but maybe I'm missing something.
Thanks,
BJ
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Peter Etheredge

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Re: Bizarre wiring on install
« Reply #1 on: May 16, 2009, 10:48:52 am »

The only thing that you can do is run new wire and, if the horns aren't 70 volt, replace them with 70 volt.

There really isn't anything salvageable about this system, perhaps bar the horns.  They probably won't want to hear that as it will cost something but I personally wouldn't bother try and "fix" it using the telephone wire and such, thereby risking having my name associated with that mess.
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Peter Etheredge
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John Roberts {JR}

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Re: Bizarre wiring on install
« Reply #2 on: May 16, 2009, 10:53:21 am »

Bradford "BJ" James wrote on Sat, 16 May 2009 09:38

I go to a site yesterday to check why they are having trouble with a paging system. Large manufacturing plant. Powered by a single 100 watt radio shack amp.

But here's the thing, I assumed the system was run as a 70v system, but when I looked at the rear connections, there was a speaker wire plugged into the 4 ohm terminal and common. But there was also a 4 wire small gauge (looked like phone cable) plugged into the 8 and 16 ohm terminals with the 2 others going to the common.
Makes me think they were trying to have 3 pairs of speaker lines running to different locations. And nothing hooked up to 70V. All the amp had for terminals was: common, 4, 8, 16, 70V

There are horns all over the plant, and the ones that I could actually hear had a bad buzz - which is the customers complaint.
I have never seem an amp wired like that. Is there any way possible that it is correct? It seemed stupid, but maybe I'm missing something.
Thanks,
BJ



Sounds like it is a mess.. If you can measure the impedance on the different speaker feeds you may get some idea of how the system is loaded.

Good luck.

JR
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Ivan Beaver

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Re: Bizarre wiring on install-Divide and conquer
« Reply #3 on: May 16, 2009, 11:38:28 am »

There is nothing wrong with hooking up a 70V loudspeaker to a low impedance tap on an amp.  Except it won't be able to get anywhere near its full rated power-unless it is a 600 watt 70V loudspeaker-not to many of those out there. Laughing

As JR said-measure the impedance of each of the lines and note where they were attached.

It all might make sense-when you look at the total impedance load on the amp-or maybe not Rolling Eyes .

Anyway-you have to ask yourself "What am I here to do".  If the complaint is about the buzz-figure that out-I doubt it has anything to do with the weird wiring on the back of the amp.

But it could have to to do with some "other" wiring errors-such as a loudspeaker conductor touching a building ground and so forth.

Unplug all the inputs to the amp and see if the buzz is still there.  If it is not-then go about finding the culprit.

If it is still there-then I would remove one loudspeaker pair at at a time (you notice I said a PAIR-not a single conductor of a pair) and see if the buzz goes away.

See if it is localized to a particular wire or not-or the unit in general.

If the amp has been working for awhile like it is-it will probably continue to work.

If the unit is faulty-then I would talk to the customer and tell them what is wrong and what it will take to fix it RIGHT.

I would either do it right or walk away.  I would NOT try to patch it up-no matter how much the customer wants you to-it will be a headache that you will never get rid of.

Let somebody else deal with gum and twine repairs and the consequencies they bring Sad
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Charlie Zureki

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Re: Bizarre wiring on install
« Reply #4 on: May 16, 2009, 01:57:27 pm »

Bradford "BJ" James wrote on Sat, 16 May 2009 09:38

I go to a site yesterday to check why they are having trouble with a paging system. Large manufacturing plant. Powered by a single 100 watt radio shack amp.

But here's the thing, I assumed the system was run as a 70v system, but when I looked at the rear connections, there was a speaker wire plugged into the 4 ohm terminal and common. But there was also a 4 wire small gauge (looked like phone cable) plugged into the 8 and 16 ohm terminals with the 2 others going to the common.
Makes me think they were trying to have 3 pairs of speaker lines running to different locations. And nothing hooked up to 70V. All the amp had for terminals was: common, 4, 8, 16, 70V

There are horns all over the plant, and the ones that I could actually hear had a bad buzz - which is the customers complaint.
I have never seem an amp wired like that. Is there any way possible that it is correct? It seemed stupid, but maybe I'm missing something.
Thanks,
BJ




  Bradford,

  Did you check some of the other horns to see how they were wired?  Or just the one you mentioned?  Only one speaker improperly terminated can cause the buzz. If it is many speakers, the Amp will shut down, going into protect mode.

   I had a similar situation recently, and some of the speaker boxes were terminated on the wrong terminals.  After checking all of the boxes and terminating them to the proper(70v) terminals the buzz went away.

 Give them an explaination of the problem .... that you'll have to go from horn to horn (every horn, don't skimp) to find the problem ... and charge them accordingly for the Labor and New wire you'll string (if needed).

Some plant maintenance worker may have disrupted the wiring and then "tried" to fix it. OR.. it was originally installed by someone without experience.

Either case... It'll never work properly if the whole system is not checked.

GO GET EM... make some dough!

Good Luck,
Hammer

ps. count the Horns installed and determine if the Amp is powerful enough to drive the system.  You may want to add a high pass circuit to kill some of the Lows.
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Hal Bissinger/COMSYSTEC

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Re: Bizarre wiring on install
« Reply #5 on: May 16, 2009, 02:18:35 pm »

The RS amp should have been your first clue that this was a "handy dandy" system. The owner either did it himself or got someone on the cheap. It's worth exactly what he paid and is is not worth your time.

Give him a price for a new system and walk away.

-Hal

Karl P(eterson)

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Re: Bizarre wiring on install
« Reply #6 on: May 16, 2009, 02:42:27 pm »

I would approach it that the whole thing needs to be redone, but say it in such a way to try and make the sale.

I also probably wouldn't say that it all needs to be redone outright, I would probably say that it all needs a thorough going over and whatever is wrong will need to be replaced.

That way if the horns and wire are good, just need a reterminating and a new amp, you'll be golden. Likewise if they are bad horns on impossible wiring with an undersized amp, you can make that sale accordingly.

If they have taken the time to talk to you about the problem, chances are there is some money to be made.

Just don't end up in a position of having your name associated with band-aids leading to future customer aggrivation.

Karl P
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Bradford "BJ" James

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Re: Bizarre wiring on install
« Reply #7 on: May 16, 2009, 03:51:34 pm »

Solid advise here guys. Thanks a bunch.
BJ
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Chris Boschen Leonard

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Re: Bizarre wiring on install
« Reply #8 on: May 18, 2009, 10:31:33 am »

I second the advice of the posters here. Offer a courteous explanation of what is really required; if the client won't go there, take a bow and exit stage left. I have learned the hard way that sometimes it's better to walk away.

The magic word is 'No'.
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Bradford "BJ" James

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Re: Bizarre wiring on install
« Reply #9 on: May 20, 2009, 12:56:07 am »

Great advise. Thanks guys.
I'm going to go troubleshot what is there to track down the cause of the hum. But, my contact person seems to think they will want the whole system replaced anyways. )
Right now they have about 12-15 horns placed throughout. I would like to replace those, and add a few more for coverage. Plus there is a newly built attached warehouse they want speakers run to. Looks like I'll be running 15-20 horns with them probably being tapped at 15-30watts depending on location. Ambient noise is around 80db. The biggest install amp I've used is the Yorkville CA1. It's only 180watts.
Any good ideas for the 600 watts I'll need?
Thanks,
BJ
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