atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Security, Alarms and Paging Valcom Class connect

I am working on a school that we have added a class connect in a new building
We have single speakers in class rooms which work fine

And there are (3) locations that have 3 to 4 speakers on them

So we had to install a V-6120 and VMT1

They were complaining about the sound quality

I noticed the the output from the V-612 (10) watt

Were wired to the the negative & the shield as opposed to the positive & Negative

The paging was working fine prior to today when I noticed the wiring didn’t look right

I did call Valcom and ask them about it

They agreed it should be on the positive and negative terminals



So I move them to the positive & Negative

And then the V-6120 started to smoke

I’m assuming it didn’t like something I don’t know if it’s a short
I did call ValCom they one of the output was damaged but then after a while it might be damaged more outputs

It’ was working fine before I moved the wires

I thought it might be coming from one particular location

I am so confused

Any thoughts

The V-6120 has 6 outputs. How many are you using? How many channels did you find that the output wiring was connected incorrectly so you changed it?
The V-6120 is designed to drive speakers that have a 25V line transformer. Are your speakers for a 25V system?
First you say that the customer was complaining about sound quality, then you say it was working fine until you moved the wires. Explain.
Have you removed all the speaker wiring from the amp and checked for any voltage on them and to ground as well as checking the resistance from each side to ground?

-Hal

Hi Hal

Thanks for responding

I am using (3) out puts

Hallway
Cafe
Media Room

They all have 4 speakers on them

The speakers have a 25 volt transformer tapped at .312 watts
2000ohms white wire

The paging has been installed for about 2 weeks

It was working (the were just complaining about sound quality)

I wasn’t there until yesterday

They were complaining about sound quality

There’s a pair of wires going from the output of the class connect
To a VMT -1 HZ then from the 600 Ohm out out of
The VMT -1 to the input of the V6120
Then from the output of the V6120 to the speakers

The output was on the Negative & Shield

I moved them to Negative & Positive and at some point

Smoke started coming out of the V612

I’m thinking that one of the 3 locations is the problem

I didn’t test the speakers for any voltage

JD

From the output of the v-6120 I put the positive wire on common (Black) of the speaker & Negative on the (white) of the speaker would this be the problem

You normally don't use shielded cable for speakers but this may have been left over from an older "talk back" system. You need to go to each location and see how the speakers are wired. Black would go to the black lead of the transformer, the white to the tap lead. At the amp the black would go to (-) and white to the (+) but it shouldn't matter. It will work just fine either way.

What concerns me is that it apparently worked with the shield connected to the (-) and the white connected to the (+)? And when you removed the shield and connected the black in it's place you let the magic smoke out. So yeah, you really need to get at those speakers and wiring to see what's going on. Are these ceiling speakers? New or old? Old existing speakers in a wall panel?

It's unlikely that a short in the wiring would cause damage like that because amps today are pretty well protected. So I'm thinking that there is some kind of voltage between the black and white. Easy enough to check with your volt meter.

-Hal

everything is brand new

Even the speaker wiring?

Who did the speaker install and wiring?

-Hal

Why did you start changing the wiring on a working system in the first place?

Did you check the speaker termination prior to moving the wiring around?

The use of shielded cable is quite common in a school install I have found.

Channels A and B have a switch-selectable EQ that might be a cause of the sound quality issue. If it's set to the HORN position and you have speakers connected or the other way around you'll end up with poor sound quality.

There was a reason the original installers used the Shield and only one wire in the pair. Is there a remote volume control in the line? Are all of the separate outputs of the V-6120 wired the same?

Good Question

I was with the original installer at the time

We are using the 10 watt outputs

It was not shielded cable

I called class connect and asked him where the leads should go and they told me it should go on positive and negative and that the shield was for the shielded That’s in shielded cable


We’re going back out in a couple of days or so once we get the equipment and we’re bringing a paging guru with us

I didn’t wire the speakers so I don’t know I don’t believe they installed any volume controls

What is Class Connect? Were they the ones who redid your work?

-Hal

Valcom Class Connect

all brand new -new building new wiring its a small building about 6 class rooms one speaker wire going to each room

hall ways -one wire going to 4 speakers
cafeteria-one wire going to 4 speakers

media room -one wire going to 4 speakers

These 3 locations have To go thru the AMP

all 25 volt speakers

there are also 2 other exiting building that are user the same system

this new building is the only one that is using a V6120 AMP

So where did the shielded cable come from? If you didn't wire the speakers and you don't know if they installed volume controls it seems like "they" (who is "they"?) messed around with what you installed. If your original cable was removed and replaced with shielded there is no telling what was done. If they knew anything they would know that shielded cable is not used for constant voltage speaker wiring. It can cause problems with the amp.

-Hal

Hal

There was no shielded cable used on the job .

when I went to the job on Monday I noticed that the pair of wires (using cross wire) coming from the 10 watt output on the V-6120 was on the Negative terminal & the ground terminal (where the shielded wire would normally go )

at this point the paging was working they were just complaining about the sound quality

there could be several reasons for this -not enough speakers ,tapped to low ,...ect

I looked at the wiring and thought that it should go on the positive & negative terminals


and during the process of moving the connections the amp stated smoking

anyways we went out there yesterday with a another AMP (Bogen) 100 watt and put these (3) individuals locations onto one zone it seems to be working fine

They only use the paging as all call at this point


I still don't understand what I did that would make this amp start smoking unless its a defective AMP


we installed this class connection in the other 2 buildings which has been working fine but this building is a little different because it has the Café ,Media room, and Hallways with 4 speakers were we need an Amp

Here is the installation manual. http://www.class-connection.com/vsp/v6120.pdf

I see what you mean about the speaker outputs with (+)(-) and ground. They do show shielded cable and the only reason I can think of is when retrofitting older systems there may be a crosstalk problem with old wiring bundled together and speakers tapped at low wattages, so the original installer used shielded cable. You will notice that the shield is only connected at the amp, the other end is not connected to anything. The speaker(s) themselves are connected between (+) and (-).

That said, undoubtedly the grounds on all the output terminals are connected internally to chassis ground. Why the speakers worked at all when connected between the (-) and ground only a schematic of the amp will tell. It's not the proper connection but it shouldn't have caused any damage. When you corrected the situation by connecting the speakers properly it certainly shouldn't have caused the results you saw.

So, now with another amp things are working fine. I usually believe Valcom makes good products but it looks like they dropped the ball on this one. Send it back.

-Hal

You still didn't answer my original question.

Why did you change the wiring at the amplifier when it was working? Just because the vendor said it should go to the negative terminal instead of the shield terminal is meaningless as they have to clue as to the actual on-site wiring.

Allow me.

Because customer was complaining about "poor sound quality" he called Valcom about it. When he told them that the speakers were connected to the (-) and ground terminals they said that was wrong, they should be connected to (+) and (-). When he did that the amp self destructed.

This is just two conductor speaker wire, black and white, no shield.

-Hal