I'm a long time "reader" on this forum, but this is my first post. I've had nearly 60 X10 devices in my house since 2004. (It's a log frame house and running wiring through the walls is darn near impossible.) After initial system debug everything has been working perfectly for more than three years -- until recently. Several week ago my son got a new desktop PC and it's causing major problems with my X10. I know it's this computer because if I (force him to) shut it down, everything works perfectly again. I've tried several different filter options including the AF120 device and the XPNR. Neither has solved this problem.

I've been using just a passive phase coupler (leviton) installed right at my main panel. With this device in place, (and the offending computer on) about half of my controls work properly (some on both of my power phases, and not all with the same house code). Some of my devices will turn on but not off, and some won't turn on OR off. I seem to have adequate signal levels (as measured with the XPTT/XPTR) on both phases, but I tried installing a CR234 anyway to see if a little signal boost would help. With the CR234 in place NOTHING works -- not one single device will turn on or off. The CR234 shows that it is receiving signal, but it transmits nothing and every incoming signal triggers the error LED. Again, if I shut down the offending computer, everthing in my house works normally. (I really like the CR234 and plan on putting it back in my system if I can find an effective way to filter the power on this computer.

I'm looking for other ways to try to attack this problem. Anybody have any suggestions? Thanks for any help.

that is weird... is the computer on a power strip? or do you only have the computer and monitor into an outlet?
if you are not using a power strip try that... if you are... try removing it...

also is there any other place you could put the computer?

Good ideas. Haven't tried the powerstrip idea, but don't think it will help -- but then neither has anything else. I have tried moving the computer to another part of the house (to my garage actually which is powered off a sub-panel) and I also tried powering the computer through an extension cord wrapped through one of those ferrite cores and those ideas didn't help, either by themselves or in combination with the other filters.

I probably need to get a signal stregnth meter (like the ESM1) to see exactly what's going on here. I might also have to try some kind of an isolation transformer. I'm even tempted to run an extension cord from my neighbor house (when he's not looking, of course) LOL.

I know there's a lot of sentiment in these forums about X10. Some people love it, some hate it. It's been flawless and trouble-free for me until now, but I'm starting to change my mind. Son is getting tired of me asking him to shut down his computer so I can try different ideas. I have to keep reminding him that I'm paying all the utilities and I'm tired of not being able to turn some lights on and off when I need to. After all, everything was just fine till he got his new computer -- at least he paid for it.

how new is the computer? maybe a cheap power supply in the unit?
I used to buy $50 case with power supplies.. but not now..

I have a ml570g2 dual ps server in my house (sounds like a 747!!!)
hp pavilion in the kitchen
antec p180 case with truetec power p/s in garage
antec 900 case with corsair 620w modular p/s in basement for gaming...
digiop g2 camera machine

I have a few computers up and running and only have 1 filter which I dont think I really even need.....

I think the guy above has the right idea, change the power supply out with a name brand unit. You still might need the filter but I would think that will do it and it's easy enough to try.

I've used Smarthome FilterLincs on a couple PCs with no noise causing X10 issues.

First question - how did you install your coupler/repeater? Many people don't install them correctly. It should be attached to two breakers that are one right on top of the other.

Critical thing here is NOT that the breakers be one right on top of the other, but that the coupler MUST bridge the two power phases. In my case they do (and I just happen to be using neighboring breakers). Good point though. Optimum (i.e. safest) solution is to use a dedicated 2-pole breaker that is of the correct type and rating for the panel it is being installed into. Turning off that breaker will insure that ALL power is disconnected to the Phase Coupler before any work is performed on it.

As a follow up to earlier comments, I did obtain a new power supply for the computer that is causing the problems. As luck would have it, I arrived while I was away on a business trip. Upon installing it, it was DOA out of the box. I'm now waiting for a replacement on an RMA exchange (it is a brand name unit and a quality one I believe). Will let everyone know how it turns out.

I had the exact same problem with my son's laptop. But the AF120 solved it. The other occasional issues I had were solved by getting one of Jeff's XTB's. Since then, I have had no problems whatsoever. Maybe you could try one of those.
Any chance you could have had a defective AF120?

The AF120 did not solve the problem. Don't think it was defective as I have two of them and neither of them helped.

I did finally manage to get the power supply in that computer replaced with a higher quality unit and this DID fix the issue (without an additional filtering). Nearly everything is good again. Tonight I'll probably re-install the CR234 to see if I can take care of the other minor gremlins in my system.