atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Security, Alarms and Paging PCM Problems

Hey all,

I just got that new amp, that is 125w. I am trying to connect it to the PCM-2000 by Bogen with 70v High Power, but the system is failing. The PA IN is connected with RCA's to the amp, and the amp is set to Hi-z. The output of the amp is connected to the pcm's PA out connection. The speakers are 8ohm and have step transformers on them from 70.7 v to 8 ohm. (two speakers)

The sound on the phone from the PCM is dimmed, and the amp lights up and changes pitches when paging is accessed, and when someone accesses the PCM's line, you can faintly hear music on the speakers. You have to be in the cieling to hear them.

Both speakers are tapped at 8watt and can be tapped at 1, 2, 4, and 8. The areas are louder so I chose to see what 8 would sound like. The amp is turned up 1/2 turn according to the PCM manual, and everything looks to be setup correctly, but has anyone had troubles like this or have any ideas I could try today?

Thanks!

Added: The amp is a bogen MT-125c. I am at the site now, and just connected a regular speaker to the 16ohm Out, and it sounds like there is no amplification whatsoever. There is an Input Level on the amp, but no apparent volume level that I can see.

Any help would be great. Thanks.

The output of the PCM is low impedance and you have it connected to a high impedance input of the MT-125. That might be a problem. You can use a Bogen WMT transformer to match the two.

What I would do first is connect an audio generator to the MT-125 input to see that the amp and your speakers are working, but you don't have that. You can use your toner- turn down the input level before you connect it and bring it up slowly to a working level.

You can isolate further be connecting the 70 volt line to the speakers directly to the 70 volt out on the amp. This will tell you definately if the amp, speakers and wiring are in good shape.

Use your butt set in monitor mode to verify that there is output from the PCM output (PA IN).

By the way, I'm moving this to the Security, Alarms and Paging forum.

-Hal

I can't find an MT-125c amp on Bogen's site, but that's what I would start with. Make sure that you can get an output directly from it, using your 70v speakers.

Which modules are included with your PCM setup?

Topic moved to Security, Alarms and Paging forum.

-Hal

By the way, are we to assume that the PCM was existing and you are only replacing the amp?

Looks like the MT-125c has been discontinued. I assume it is similar to the MT-250. That does have a switchable input for a telephone line such as from the PCM. Move switch to Tel line and connect to the low impedance input.

-Hal

yes it is an old amp.

Thanks for the input. I figured out what was wrong with the amp, The input from the PCM is jarred, and the rca jack can't be inserted more than .5 way otherwise you get an un-amped sound from the speakers. I tried the low-impedance input, but that didn't work either. Works perfect now, runnign 70v.

I did monitor the line with a buttset from the pcm like you said, it was working perfect, and I toned through the amp also, tone worked perfect after adjusting that rca jack.

The PCM's program tone helped a lot too.