atcomsystems.ca/forum Forums TDM Business Telephone Systems Mitel Telephones & Systems Mitel SX20 Console

Hello,

We currently have a Mitel SX20 system with 55 extensions and four incoming lines. It's been extremely reliable for two decades. A few days ago we had our first major problem.

For calls using the console, the other party can barely hear the person using the console headset. Under normal conditions it seems dead but it's just really, really faint. This is for both incoming and outgoing calls through the console. It does not matter if the call is from/to inside the build or outside. Extension to extension is fine as in extension to outside and vice versa. We have changed the handset, the cord, the adapter and swithced sides for the adapter. The problem is the same. We don't know if the problem is with the console, the CPU card or the Misc card. Maybe a stray wire inside the cabinet? Any help would be greatly appreciated. Thank you.

Can you plug the console directly into the phones system? That would eliminate a potential problem with the feed cable.

We did plug the console directly into the cabinet to bypass the daisy chained cables. Same problem. Maybe we should try a different cable to connect the two?

Those old consoles use a carbon mic handset and those can start doing this. Try opening up the mic on the handset and clean the contacts on the back of the module and where it connects. Another thing we used to do is rap the module on the edge upon a desk that can unpack the carbon inside. Don't use a liguid cleaner, just use a knife edge to scrape the surfaces.

If you can, try eliminating/swapping the 'daisy chained cables as much as possible!? I'm sure a few techs on this board would LOVE to comment on daisy chaining cables!
There is a daughter board that resides on the Main Control Card who's purpose is to support the console. If it's not the cabling, that'd be the next place I'd look.

Thanks everyone for the suggestions. I've changed the handset with one I know works and the problem still occurs. I've also tried the handset on another phone and it works there so moving down the line changed the cord and then the adapter and then the socket with no avail.

Next I tried all three cables that were part of the daisy chain. Unfortunately it did not fix the problem but I did clean up a bunch of dust bunnies. I guess I'll look at the cards. I'd just like to at least rule out the console at the problem before looking to replace a cards(s).

Again thank you everyone.

BlueD, where did you get the replacement handsets. Not just any handset will work, even if it is identical in size, shape, and even color. It MUST have a carbon granule microphone cartridge, and a dynamic receiver. This particular combination is not nearly as common as it used to be. Most room phones sold in the last 10-15 years have an electret microphone in the handset, that will NOT work on an SX20 console. The transmit level is VERY low. What happened immediately prior to the handset apparently failing. And is this a Handset, or a headset as your first post indicated. The reason I'm asking is that in all my years (30) of 10's, 20's, and 200 analog consoles, low transmit has never been anything but the handset microphone cartridge. If the microphone leads are broken, or intermittent, end to end, the console will go into night service.

Lightninghorse, it's a handset - sorry for mistyping. I used the handset from a regular room phone to test the console. Before that I checked the microphone portion of the console handset and it looked the same as the test handset. I have some older phones in storage and will try one of those handsets tomorrow. Thank you for the advise.

I can not thing of anything out of the ordinary that happened immediately before the handset failed. There was a brief power outage to the area that morning for under 15 seconds but the handset was working until the afternoon. I was thinking it may have caused a short somewhere but everything else is still working and the handset didn't start having problems until hours after the incident.

Well I tried the oldest handset I had (around 20 years) and it did not make a difference. The current handset has been there for years and looks to have an electret microphone. I friend found some one else with a SX20 and said I could try the console there sometime next week. At least I may be able to eliminate the console as the problem and move on to the cards.

Yes, the only way to eliminate the console is to replace it with a known good one. Maybe, after 30+ years, your console has finally 'crapped out'!
Speaking of 30+ years, keep in the back of your mind that once you power off your system, and start moving boards around, it may not come back up!