Nice note on http://www.seeedstudio.com/wiki/DSO_Quad:Upgrading_Firmware#Hardware_V2.72 
Nothing about it wroted in package, nothing about it on pages with calibration… It is standard solution ? User will be “unsolder the shield in 3 spots, remove the surface mount components” ?
Could be actualised somewhere parameters, for what this DSO QUAD can be used ? 80Vpp, when 50V can damage inputs ?
Hi msmola,
Thanks for reminding. We’re now confirming with the designer about the characteristics of the TVS devices.
Will update the doc and info you as soon as we get any conclusion.
Thanks again.
Hi msmola,
If your DSO’s product name is “QUAD”, then you can forget that paragraph at wiki (that paragraph is for a version named “DS203”), because the designer has made corrections on D2 and D3.
The rated operation range described on guide - 80V - can be trusted. You can measure test point and/or calibrate with the voltage over 35V.
good news for me. thanks
But here on forum i can read “DSO203 Quad” or “DSO QUAD”. It is not same device ?
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.
It’s a question for far history. DSO Quad and DS203 belongs to same series. They’re very much similar. But now SEEED sells the branch Quad.