atcomsystems.ca/forum Forums TDM Business Telephone Systems Mitel Telephones & Systems Express Messenger serial port trouble

Is anyone familar with component level repair on the Express Messenger? I have one with a bad serial port and I hate to pay mitels fee to get it repaired. Any idea which chip may be shot? It is most likely a line driver chip but without a drawing of the circuit I just dont know where to start. Now I know most of you are thinking, Is he really going to try to repair it himself! I have been doing this kind of repairs on two-way radio and broadcast equipment for over 30 years. If I dont think I can replace the part correctly I wont attempt it.

Thanks for any help

It is hard to say but I would trace down TX & RX from Com1 port to Chip and see or this can possibly be a target. Usually Mitel uses standard components.

I hate to backtrack here but have you put a line tester on it to make sure it is bad? Oddly enough I have never had a serial port go bad on one of those cards. That being said if it is it is probably just a driver chip - the ones on the Xiox CAS could be had at radio shack and were pretty easy to change.

I have tested at the com port and I am sure it is bad. I can backtrace the connections from the port. I was just hopeing someone had tried this and could help me avoid the backtraceing.

In all probability, they are surface mount 1488 and/or 1489 receiver and driver chips. (Never can remember which is which) That's what they were using on the last EL MCC I looked at. Design vintage is about the same, so.... Any idea what may have taken the port? Only thing I can think of is a boomer from a PMS system. That's why I put protection on EVERY PBX port. Trunks, extensions, 232's, page, MOH, power, everything. And a #6 Stranded ground to a VERIFIED EARTH GROUND! With a buss bar that ALL groundable stuff connects to for 1 COMMON ground point, NOT connected to power ground. John C.

I dont have any idea what took the port out. There have been a lot of thunderstorms in this area over the last month but the customer said the Voice Mail pms quit over six months ago. It may have been in warrenty then.
I agree with you on common point grounding and on the protectors on everything connected to the system. I always use number 6 or larger wire keeping it as short as I can and avoiding any sharp bends in the wire. I have learned a lot about grounding from my work in the broadcast industry. When you have a 400 to 600 foot tower(lightning rod) you better have a good ground and everything connected properly. Two different grounds is begging for trouble.