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[JeffVolp]

I installed Levtion 16400 4-button keypads when we built our home 15 years ago.  The one used to trigger supplemental cycles for our irrigation system started acting up about a year ago.  While all other X10 controllers have been working fine, that one sometimes required multiple button presses before the zone valve would come on.

Since the LEDs normally display zone valve cycling under control of our Ocelot, I recently noticed its LEDs were not indicating what was actually going on.  A quick check with the XTBM confirmed that while the LEDs were still responding to button presses, it was neither transmitting nor receiving anymore.  I swapped it with a 16400 spare, and now everything is working again.

I wondered what happened, and opened it up by extracting the press-fit pins holding it together.  Since the LEDs were still working, the failure had to be associated with the X10 powerline interface.  From previous experience, I suspected the .22uF 250V coupling capacitor common to both the transmitter and receiver.  After unsoldering one end, I confirmed it had failed as it only measured about 400pF.  I replaced it with a .22uF 400V capacitor, and now the unit is working again - pumping out almost 5Vpp.

The fix is not too difficult - probably took about 10 minutes.  So if you have a failing X10 XPT or Leviton 16400, this is something to try before tossing it in the trash.

Jeff

[Brian H]

Nice catch.
Did you happen to check the filter caps in the power supply? Probably a good brand back then.

[JeffVolp]

Did you happen to check the filter caps in the power supply? Probably a good brand back then.

Just inspection.  There was no evidence of any leakage, and the fact that the LEDs were working led me to believe the power supply was fine.

Jeff

[toasterking]

Wow!  Thanks, Jeff! 

I have many of the Leviton 16450 series keypads in my setup, but I use them with the X10 XPT "version A" transmitters, which seem externally identical to the Leviton 16400.  The LEDs on all the 16450 series keypads even work, and illuminate when an "ON" command is transmitted for the corresponding X10 address.  They are compatible with XPT "version A" (image), but not the older XPT (image).  It is easy to visually distinguish these two versions.

Anyway, my XPT units have gradually been failing.  What seems to happen to me is that some keys intermittently trigger the wrong unit codes (e.g. a different light will come on than the one I requested), and the fault becomes more frequent as time goes on.  Not all codes are affected, and looking at the X10 PLC protocol specification, the morphed codes all appear to be from one or two 1s that are flipped to 0s, so a weak power supply or perhaps even coupling makes sense.  The signal output also becomes very low.  I've been replacing them once they get to be more of a risk than a benefit to use.  But I've not been able to answer the question of what I will do once these are discontinued.  I have a "sick" one now and will try this on it and report what happens.

The clock timing on these is also all over the place, according to my XTBM Pro.  The new ones put out a signal close to 120 kHz, but my old ones seem to range from 110 to 126 kHz.  That probably means I have a second component to replace to correct that fault.