I'm staying with my inlaws for a few months, and to earn my keep I'm fixing everything they've broken in the last 15 years around the house. The latest challenge is the intercom system.
It appears to be a M&S MC350. The problem is that when we turn up the Speaker knob (bottom right) we get a squeal that will broadcast to any active room units (not sure what you call the...units in the...rooms. They'd be clients if this was technology from my generation). If the system is left plugged in, the squeal will come and go.
The system was installed by dad, who says the runs to the rooms should all be straight shots, but all the connections on the back of the board, connecting all the remote units to the (server?) are just twisted together and electrical taped. His theory is that there's a loose dusty connection somewhere, so I'm planning on soldering plugs on all the connections to make sure they're solid. Mom's theory is that since the squeal comes from the Speaker knob, the pot could be bad, which is possible, but it does still change the volume. If I get the plugs in and the connections soldered and the squeal remains, I might look at that.
This almost looks like a radio interference issue, since the squeal comes and goes, but I'm not nearly familiar with this stuff enough to just start sticking resistors on there. I haven't found any forums that address home intercoms specifically, and I'm not even sure if this is the place for it.
Any help will be appreciated.