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  • skatz
    replied
    You might need to visually inspect the speakers for surround damage. Some of them seem to be approaching 40 years old and may not be making sound because the surrounds are gone.

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  • JItter
    replied
    This morning instead of the toner i hooked music up and walked around listening to speakers. I only turned the music volume up maybe a 16th of a turn it was putting out 9V and it was pretty loud in the building. I found 2 speakers with no volume and i am not 100% sure if the kitchen ones are hooked up. At least i seem to have narrowed it down to around 5 speakers. As for the paging it still seems off. I turned the Tel volume down and it is much clearer, but not very loud. Once i check the 5 speakers i might play with the ALC and what not

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  • STIchris722
    replied
    Originally posted by JItter View Post
    I have a tone generator......When you say run power to 23.3 volts is that simply a matter of slowly turning up aux amp volume till it reaches that voltage? Is the purpose of this to send a tone through all speakers to see what is working? I have read about conduit for 70V systems, ill have to see if I can find that code. I think my longest run once I get things how I want will be about 300ft. Is there a disadvantage to using 25V over 70V? The new speakers I have been getting you can hook up either way.
    That would be turning up the actual output volume control; at least that is how I understood it:

    "Slowly turn the amplifier's volume control up until the meter reads 23.3 volts (1/3 voltage). A 23.3 volt output is used instead of 70 volts for some good reasons; mainly because pushing the system to its upper limits could damage aging components or human hearing should anyone be near the speakers! This tone will be penetrating. It may be wise to make arrangements to do this after regular business hours."

    The way I am making sense of this is that you shouldn't be pushing your amplifier to the full 70V output all the time as it isn't necessary. Most zones probably have a volume control knob that lowers the volume anyways. Again I'm not expert at this and am flying blind trying to understand your debacle. I feel for you though!

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  • JItter
    replied
    I have a tone generator......When you say run power to 23.3 volts is that simply a matter of slowly turning up aux amp volume till it reaches that voltage? Is the purpose of this to send a tone through all speakers to see what is working? I have read about conduit for 70V systems, ill have to see if I can find that code. I think my longest run once I get things how I want will be about 300ft. Is there a disadvantage to using 25V over 70V? The new speakers I have been getting you can hook up either way.

    Leave a comment:


  • STIchris722
    replied
    Originally posted by JItter View Post
    i believe it is a dc function where there DMM provides small voltage. Any guides i have found explained how to do it and most were saying with an 8ohm speaker i should be reading around 6.5. When i tested new speaker i unhooked the other feeds from the amp and only had the new speaker hooked up. One thing that was odd is I found a punch board in the ceiling. Coming from the amp i only have 2 feeds, but when i toned the wires going into the board i was getting 3 feeds. i don't know if one was spliced somewhere or what.
    Forget my first comment about the DMM. I was thinking of a standard tweeter being tested for impedance.

    From what I am reading it sounds like you need a 1KHz tone generator and a DMM. Hook the tone generator into the aux input of the amplifier and the DMM between 70V and common on the output side with all things hooked up. You want to then run your power up to 1/3 (approx 23.3V). After doing so I would rewire every speaker from the main transformer. Also consider most jurisdictions require 70V paging line to be ran in conduit. Your's may be different though. Also eliminate and/or trace the punch board.

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  • JItter
    replied
    i believe it is a dc function where there DMM provides small voltage. Any guides i have found explained how to do it and most were saying with an 8ohm speaker i should be reading around 6.5. When i tested new speaker i unhooked the other feeds from the amp and only had the new speaker hooked up. One thing that was odd is I found a punch board in the ceiling. Coming from the amp i only have 2 feeds, but when i toned the wires going into the board i was getting 3 feeds. i don't know if one was spliced somewhere or what.

    Leave a comment:


  • STIchris722
    replied
    https://www.parts-express.com/resources-70-volt-system

    Someone correct me if I am wrong but checking impedance is a DC function with a DMM correct? As far as what is going wrong I don't have a ton of experience with constant voltage systems. Have you disconnected all speakers and plugged in the single new one to see what happens? That would probably be my first attempt at isolating the issue.

    FWIW I would not use shielded cable as it only adds additional capacitance. I would stick with 16awg twisted pair plenum cable.

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  • JItter
    started a topic PA System Question

    PA System Question

    Hello im new here... I am the maintenance director in a nursing home and we recently started having trouble with our PA system. We have roughly 40 speakers on a Bogen TPU250W amp. We are only using the TEL input on the amp which comes through a Viacom box. First the speakers in our kitchen and dining room went (6 speakers total) now the rest of pages are quiet and garbled. Some of the speakers are from the 80s, but the amp is only a couple yrs old. I am trying to figure out where to start troubleshooting. It is a 70V system and and speakers range from 1w to 4w and are 8ohms.
    I have used a meter a few speakers and getting weird readings. I have a brand new 8 ohm bogen speaker than you can set from 1/8thW to 4W. My ohm meter is reading like 260ohms. I should note i hooked the new speaker directly to the amp and did a test page and it was crosstalk versuslThe 1W speakers i tested currently in the system are reading 116ohms. I thought my meter was bad so i tested a resistor on another circuit board and it was perfect. I do not know what I'm doing wrong. The wiring itself is pretty much a cluster and eventually want to redo it. In the meantime, what is the best way to go about troubleshooting?

    On a side note, my longterm plan is to run one feed from the amp to a terminal block. Then have each section of the block feed a section of the building. That way if something goes wrong I can at least narrow it down easier. I am thinking i need 700-800ft of wire. Would shielded 18ga or 16ga work?

    Thanks
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