[TenTec] OT: USB to Serial interface

[Kim Elmore <cw_de_n5op@sbcglobal.net>]

I have recently noticed that one of my USB-to-serial converters is 
misbehaving. It's a no-name unit that uses a Prolific chipset and has 
served well for years. It is the one I use for PTT control of my 
RigBlaster.  After the system boots, every 15 s I get two very quick 
"dits." If I move it to another USB port, the problem vanishes. The 
three other identical units I have seem to be fine. I've ordered new 
USB-to-serial units but they have yet to arrive.
Has anyone ever noticed anything like this on their units? Is this 
just another failure mode for these things?
Kim Elmore  N5OP