Home Automation

How to repair your Insteon PLM modem

The last few years I have been contributing to OpenHAB, an open source home automation project. Together with my son Daniel I wrote a module that allows the OpenHAB system to control the Insteon light switches in my house. I wanted to be able to simulate presence, switch off all light switches with one button, and have lights and fans turn off automatically when there is no motion detected for a while.

Insteon uses a modem (called a PLM) to communicate with their device through both the power line and via radio frequency signals. There is a somewhat tedious setup process of linking the switches to the modem, and the modem keeps an internal database of what devices it has been linked to.

After three years my PLM modem crapped out because of a well-known flaw: the capacitors of the power supply are under sized and/or of low quality. I was already preparing to relink all my devices again when I stumbled upon this thread. The instructions are for a serial modem, but they worked the same way for my USB based 2413U.

The repair is actually quite simple and very nicely described in the the thread mentioned earlier. I decided to add a few pictures so you know what to expect. You will need some basic soldering equipment and skill. Do not attempt to repair your PLM if you don’t have a basic grasp of electronics. If you screw up and are unlucky you can cause a fire or electrocute yourself. You have been warned.


In the picture above, the top row shows the new capacitors, below are the old ones. Watch out to install the capacitors the right way round: they are of the “polar” type, meaning you have to watch which leg is + and which one is -. The positive is clearly marked on the board, the negative on the capacitor. Have a good look at the old ones before you solder them out so you understand the polarity labeling.

Given how cheap the material is I ordered two sets of replacements. That’s why you can already see the new ones installed on the board. The replacement capacitors came from Mouser Electronics, following the instructions in the thread mentioned above. Cost is about $2.50 for a set, plus about $5 shipping. Here are the Mouser Part numbers and how many pieces you need of each:

  • (1) 647-UST1C100MDD 16volts 10uF
  • (2) 661-EKY50ETD100ME11D 10uF 50 Volt (you need two of these!)
  • (1) 647-UTT1E101MPD 25volts 100uF
  • (1) 80-ESX106M400AH4AA 400volts 10uF 20%

After the repair my PLM modem worked again! However, it had lost all its link database state! I have no idea why this happened, but it did. Fortunately I had saved the modem’s database with this little tool that Daniel wrote for me: the Insteon Terminal. I restored the database and everything worked like before. Even though I had to restore the modem database, at least the insteon address of my PLM didn’t change, saving me the work of changing the modem address in all the linked switches (even that can be done with the Insteon Terminal, but it would still be tedious).

Not only does the modem work now again, I feel like my modem is actually better than before. Thanks again to the folks at the repair thread. Have fun!