atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Security, Alarms and Paging Typical cause of pop/crackle noise from paging speakers

Do any of you suppose that the humidity was too much for this thing being in that outside closet and maybe it just needed to dry out for a bit? Not making a peep now.....

What do you think putting the speakers on the 25 volt output is going to prove? It's just another tap on the output transformer. And your voltage/current measurements mean nothing, it ain't that easy to measure wattage else why would you need an impedance meter?

If you are absolutely sure that this is not coming from an input or dirty controls are the culprit, if you still think this intermittent problem occurs when the amp heats up it's the amp. And no, overloading the amp won't cause this kind of problem. Repair or replace.

-Hal

Definitely not from an input, as the only thing connected to it is the phone system, and it does it even if you're not paging.

As far as "proving" anything by putting the speakers on the 25 volt side, I was thinking the fault might only exist on the 70 volt side. As I stated, this is my first time trouble shooting these, so you'll have to bear with me as since I didn't design the thing I don't know any better.

Last time I checked watts is a function of Volts times amps. I figured since I don't have the proper meter, this would at least tell me if there was something really wrong with the draw if it was ridiculously high for 26 speakers. Which I'm assuming are tapped at 1 watt, since the one i pulled down was, and the math makes sense.

I guess this is not the way to do it, and I'm sorry if I offended your delicate sensibilities.

Thanks for at least one useful(?) piece of advice in that too much current draw won't cause the issue!

Using a multimeter to check those values won't tell you anything really. The 70V and 25V are RMS values and even if you have a true RMS multimeter it won't provide the correct reading (multimeters are designed to provide the correct RMS reading only at 60hz, although some of the cheap ones do give a close reading). Without an impedance meter, the next best this to use is an O'scope and calculate the RMS value.

The only way the values are going to be correct is when you input the test signal at the correct level and then take your reading. You'll never see an actual 70V or 25V signal on the lines as an example the last system that I worked on had a changing voltage reading around 4V.

Having 26 speakers can mean you are using 26 watts or up to 360 watts. It's the tap setting that you need to figure out if you don't have an impedance meter.

Here are a couple of good sources that will give you a better understanding on how this works.

Guide to constant-voltage systems
A Handy Tool for Measuring “Constant Voltage” Sound System Impedance and Calculated Power

doing a google search for 'testing a 70v system using a multimeter' will provide you with a wealth of information.

CAUTION - As with all google searches there is a lot more junk than useful stuff so be sure to cross-reference what you find with other sources

Hey, if you don't like the advice here I'm sure there are other places that might be more to your liking and won't hurt your feelings.

-Hal

No hurt feelings here, I was just busting your you know whats a little.

At any rate, this thing has been up and running for 3 days now with no reports of failure. So maybe it was environmental.

Thanks for the links! You're right about there being a lot of different crap online about these systems. It's hard for someone new to these systems to differentiate between good and bad advice. Thanks again for some links from someone who can verify the reliability of the information presented.