This might get a bit long, and I'm not really experienced with this stuff, but any advice/suggestions you all could offer would be greatly appreciated.

Here's the setup:

1. We have the Archer A9 in the office, connected directly to the Modem;
2. The office computer is connected via ethernet to the A9;

3.  There are a few other computers connected via ethernet, along with a couple of hubs, thoughout the 3-story house, all using CAT 5E cable that really can't be accessed any more. HOWEVER, all connected computers connect fine and run at good speeds;

4. The A9 has both 2.4 and 5.0 wireless networks running . . . connections to the network are fine and run fast.

5. For this topic, let's just call them MAIN 2.4 and MAIN 5.0

For some reason, our son's computer doesn't connect that well to the wireless network when he's working in the basement. So, we took our old N750 Wifi Router and hooked it up to the ethernet down there and set up a different wireless network just for the basement. That router is accessable via 192.168.1 and not the 192.168.0 that the Archer A9 uses. With me so far? Again, this router is connected via ethernet to the in-house wiring, which is connected to the A9.  For the sake of this discussion, we'll call the N750 Wireless Networks SON 2.4 and SON 5.0

Here's the issue. Anyone can use any connection or wireless network, anywhere in the house, with no problem EXCEPT . . .

If our son signs on in the basement, using either SON 2.4 or SON 5.0, the wireless networks coming out of the basement N750, the main computer upstairs, which is connected via ethernet to the Archer A9, loses internet.  Again, using the WIRELESS network in the basement (SON 2.4 or SON 5.0) makes the office computer upstairs disconnect. HOWEVER, the office computer upstairs CAN connect via WiFi to the Archer A9 . . . the one it's connected to via Ethernet.

If our son connects to MAIN 2.4 of MAIN 5.0 in the basement, if it's working down there, everything's fine, including the ethernet connection to the main computer.

So, again; connecting to HIS wireless network (N750) in the basement, forces the Main Office Computer (connected via ethernet to the Archer A9) to disconnect. BUT the computer CAN connect to the Archer A9 via wireless, regardlss of what network he's using.

Told you this might get long. Hope I made this clear . . . it's a little strange.

All routers/modems/computers have be rebooted and, again, there's no problem connecting via WiFi, just the hard wired ethernet connection.

Any thoughts?

Thanks so much for any advice,

asrseattle