I have a Partner ACS R8 system with 1 308EC module installed and 13 extensions on it; 12x 34D phones and 1x 16D.

Having issues with the microphones on the phones at certain extensions failing to work. It will be either really low volume, or not work at all regardless of the MIC mute button. Happens on both internal calls and external calls. Replacing the phone does not fix the problem, it stays with the extension. The problem comes and goes, but it is usually the same extensions affected. Strangely, in some of my testing/troubleshooting, I discovered that unplugging some phones appears to fix the issue. It doesn't seem to matter what phones are unplugged, just as long as some of them are. 3-4 unplugged usually takes care of it.

No other functionality of the phones are affected. Handsets work 100%.. It's just the speakerphone mic! The problem started a few months ago and keeps getting worse. There have been no wiring changes.

Anyone have any ideas?

I've never seen that problem but as these things age I suspect we are going to see some problems that never affected new systems. I'm thinking about the dozen 34D phones you have. 34Ds draw the most power and I'm wondering if the power supply in the ACS is going bad.

-Hal

I'm going to guess that extensions 19-22 work fine, and the mic issues are only on the 10-18 extensions? If that's the case, I'm with Hal, sounds like the power supply. I've seen replacement power supplies online for the various modules. If it were mine, I'd replace the power supply. In someone's business... I don't know. You'd have to weigh it out. They are pretty easy to replace. I've replaced a couple in 308EC modules, but changing one in a processor is no different. The power supplies themselves are different, but installation is identical. I use a small flat head screwdriver to pop the clips holding the clamshell together, then the power supply just unplugs and lifts out. It's super simple. Just my two cents. I enjoy fixing things rather than replacing them, so if it were me, that's what I'd probably do.
If I had to hazard a guess, the caps in the power supply are probably dried out and have lost their ability to supply clean and filtered DC to the module. The power supply sits in the top of the module so all the heat goes right up through the power supply and slow-roasts the capacitors.

Here's one that I found in less than 8 seconds.


Ebay power supply

I agree, PSU.
Go to Refurbered Supplies to get new ones .

Refurb Supplies is the seller of the one I linked to. I've bought all sorts of stuff from them. Always had excellent luck.

The worse affected extensions are indeed 10-18 on the processor module. Unplugging 2-3 phones from just the processor module solves the problem. So I would agree with the power supply being the likely culprit. There is also one extension on the 308EC that experiences the same issue from time to time.

Maybe this is also why the overall volume, particularly the outgoing volume on the CO lines is low. It did not used to be that way. We have had some callers complain they have a hard time hearing us.

Might just be time to swap in a IP Office system....

God no! Just replace the Partner mods as necessary.

-Hal

Either IP Office or a Hosted System.
Your wonderful Old Partner System has lived its life.