I have the plm apart currently, but, i'm sure you know there is only the one led on the plm and it lights green as soon as pluged in As far as the isy, as I recall, it only showed power on and rx lights. There may have been flickering lights on network switch where isy was connected but I didn't note that. I've ordered a set of capacitors and will try swapping out those when they come it, but not sure that will fix plm's troubles. Are you saying I could use the 2412N with isy? If so, what would need to be done, ie. disconnect a fuse inside? thanks if this could be done, it would verify the plm, 2413S is bad, may allow use of the 2412 until it goes.