Originally written and posted Saturday, 2 March 2019.
Content last modified Saturday, 9 January 2021 .

Common Failures with X10 Modules and Controllers and Their Repair

Alert exclamation point in triangle IMPORTANT:This information is provided AS-IS, for informational purposes only, with no warranty whatsoever. Neither Sonic Purity nor anyone at Siber-Sonic.com can control your ability to successfully and safely utilize this information, and we accept no responsibility for anyone’s actions (beyond our own) related to the content of this website. X10 equipment utilizes the A.C. power line, which is dangerous. Do not attempt any of these adjustments if you have any doubt about your ability to work safely with household powerline-operated devices. It is your responsibility to know and understand common safety procedures, especially those involving electricity at potentially dangerous power levels!

Note: I am not calling out part numbers, e.g. C6 or R18 or Q1, because these not only vary from device to device, but also within production runs of the same device. I have found that X10 tends to use the same part in each position even when the call-out nomenclature changes. In other words, in controllers, the circuit which outputs the PLC signal sometimes has a driver transistor. When it does, it is in my experience a 2SD667, whether it’s called Q1 or TR1 or something else entirely.

Assorted Failures of All Kinds: Electrolytic Capacitors

The design of X10 circuits demand a great deal from electrolytic capacitors, especially those in power supply circuits of X10 devices lacking a power transformer, which is the majority of them. Always visually inspect all electrolytic capacitors in X10 devices having issues, and replace any with visual signs of trouble. Those with access to sillyscopes (oscilloscopes) may consider checking waveforms across various electrolytic capacitors in malfunctioning X10 devices, to see whether the waveform is reasonable or not.

Controllers Aren’t Controlling Modules

It is well known that X10 systems suffer greatly from even small amounts of powerline interference, which is nearly ubiquitous in the post-1970s electrical environment. This page does not cover interference issues—they’re too complex and nuanced, and have been well-covered on other sites. Same thing for insufficient cross-phase coupling of X10 PLC signals.

This page covers situations where interference is not involved and powerline cross-phase coupling is irrelevant or known to be adequate. In other words: what had been a working X10 system with no changes (subtracting as well as adding) in terms of household electrical devices capable of altering X10 PLC signals (the vast majority of modern electronic devices, which is why legacy PLC systems like X10 have a bad reputation for reliability and are not especially popular for new installations).

Put another way, this page covers failures in X10 devices themselves, in a known-reliable home powerline environment.

I have seen this several times with an SD533 Sundowner mini-controller and once on a CP290 home control interface. Each time was a different failure. Always the indicator on the controller indicated that a signal was going out, when the actual signal was not what it was supposed to be, thus failed to control anything.

Insufficient or No PLC Signal

All sorts of failures may cause this. Here are ones i’ve seen:

Like the electrolytic capacitors, the X10 designers work the PLC output driver transistor hard, making it worth checking. Note that many X10 devices have no PLC driver transistor. When they do, in my experience it’s usually a 2SD667.

PLC Signal Present, But Still Not Controlling

This was a weird one i saw on my CP290. It only happens with more sophisticated controllers such as this model, which have circuitry dedicated to timing where on the A.C. waveform the X10 PLC signal will appear.

For right now i’ll refer you to my CP290 home control interface page. If i find in my own life or receive site correspondence from others that it’s a more general issue, i’ll rewrite and put it on this page.

Modules Which Used To Work Intermittently or Totally Fail to respond to PLC Signals

Far and away the most likely scenario is that there is a new electrical device ripping electronic farts (e.g. putting out powerline noise and/or sucking 120 kHz PLC signals), or a device has been removed that has thrown off the electrical impedance on some circuit enough to degrade the PLC signal at the module.

I had one module which had worked well for years, then gradually became more and more unreliable, with no changes in the electrical environment. Alignment cured the problem. It was an old module and electronics do age. The amplitude of the PLC signal did not seem that low, however i was able to realign this standard lamp module’s PLC transformer for peak resonance and restore reliable operation.

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