Have a old partner II with incoming call ringing being heard on existing calls . Sounds like motorboat thru receiver and extention speaker. Verizon copper co's but they supposedly checked ok per Verizon tech. 2 cabinets with 4 206 mods and 3 400 modules. Custom line appearances where they start with line 5 through 20. 1 to 4 are not used. External vm with 15 phones. Any ideas? I'm being subbed out to check on this problem.

Bad 206 modules. You'll need to move the lines to still different line ports, and reprogram the line appearances to look like nothing is different. Don't forget to set any auto attendant/call coverage settings from the old to the new.

That was it. Changed the first 206 out and noises disappeared. Thought that might be it, but was afraid to power down and losing all programming if memory battery on processor was bad. Worked out fine, Thanks TTT

Just a quick note. One person Still heard rings on ext 20. Had to change out 2nd 206 and 400 card to fix totally. Might have only been the 400 mod but they also had multiple bad ports on both 206s. Check it all out before leaving. Duh.

Would an upgrade to an Avaya Partner ACS R6 be an option?

Sure, but its not my customer. Plus they have 14 co's and 15 phones plus
External 4 port partner mail. That's why the Partner 2 with 2 cabinets full. I'd have to change to all 308ec mods too.

It's truly time for a upgrade.