Here is a way to test whether you have these protection diodes in place without opening anything up.
Connect a variable voltage source via a series resistor of say 47K to an input direct (x1 probe). The resistor will limit the current to a safe value when the protection diode kicks in if it is present. Without the resistor the diode can get destroyed.
Set range to 10V DC with trace near bottom of screen. Increase source volts. Trace on screen should rise in sympathy. If your device has the protection diode then at some point the trace will clamp and not rise as you increase the volts. The clamp voltage is typically 35V for these devices but could be as high as 60V. I wouldn’t go higher than 60V anyway and care needs to be taken if the supply can generate higher voltages.