I have same problem.
I have jtv-69 and when battery is put in a series of lights at the back response.
But the variax modeling will not do anything anymore.
No lights, no response when using the variax knob.
Also not for the tuningknob.
Using just jack, no vdi.
Battery has been charged.
Could not find any usb connection.
Q1: How can I reset de JTV-69 standalone?
Q2: can i use standard utp (networkcable), as i do not have VDI cable (yet).
Q3: how do i reset/connect to my PC /workbench - can i use utp cable?