424 and 414 have developed random high frequency popping sounds

[BlankFor.ms]

Both of my units have developed a similar problem. After being on for a couple of minutes they will begin to pop randomly. It subtle, but loud enough to make them unusable. The popping does get picked up in recording.

I recorded the sound, here's a link: https://soundcloud.com/blankfor_ms/tascam-clicking-problem/s-ImfVe

This is a new blank tape, never used, simply playing.

Does anyone have any ideas of what could be causing this, or how to fix it?

I am using original power adapters for both of them. I also have a PortaOne and a Porta02 and neither have had this problem.

Thanks!

 

[SkywaveTDR]

I would need to see the units to make sure but to have two independent units do the same thing is highly unusual and would point to a common source part power supply or interface that is hooked to them. Many people have trouble with analog devices only when they hook them to computers- these computer interfaces have noise sources of their own and sometimes feed the signal back to the analog device which is just a setting in the hardware.