hi.. we have a very old yara n sensor {has the square connecting plug]. however i plugged in the x20 and got the dreaded burning smell along with some smoke. Just thought id jump on here to see if there are any x20s out there for sale before i look about getting this one repaired. I read on here before somewhere that the x20s are trouble some and not worth fixing but our sensor will only work with the x20 im told, and we dont do enough to justify upgrading the whole sensor.