Products > Test Equipment
Hantek DSO2xxx schematics
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gnuarm:

--- Quote from: pcprogrammer on December 28, 2022, 07:46:49 pm ---
--- Quote from: gnuarm on December 28, 2022, 06:27:58 pm ---Am I looking at a modified schematic?  What you think it should be?  If so, I agree. 

--- End quote ---

Yep that is a modified schematic. The original is here: https://github.com/pecostm32/Hantek_DSO2000/blob/main/Schematics/Mainboard/Waveform%20Generator.png

--- End quote ---

Ok, but 50 ohms is not going to make much diference really.  If the input is connected to +12V that's going to be 240 mA.  I use the diode clamp to prevent an ESD surge from reaching the chip inputs.  Fed into the power line means the capacitance of the power bus will absorb most of the surge.  The devices themselves typically have ESD diodes into the power rails, so in reality, the added diodes are just protecting the on chip diodes. 
pcprogrammer:
And that is why the manual of the scope states that the allowed voltage on the trigger input is 0 - 3.3V only.


--- Quote ---External: External trigger input, it is on the front panel of the oscilloscope. The external trigger signal must be a 0-3.3V [CMOS] waveform.

--- End quote ---
DavidAlfa:

--- Quote from: gnuarm on December 29, 2022, 01:11:54 am ---but 50 ohms is not going to make much diference really

--- End quote ---

Really? The +-5V supplies have a load of about +600, -250mA.
Without resistor, a wire moves, the clip snaps, briefly touching 12V, but you have very low impedance path to +5V through the diode, being such small diode it'll will blow apart, and pray nothing else gets damaged.
With 50R in series, you'll have (12-5)/50=140mA max, the resistor will survive a quick "touch" instead destroying your frontend.
And if you hold the connection for longer, the resistor will dissipate ~1W, will act as a fuse, limiting the damage.
gnuarm:

--- Quote ---destroying your frontend
--- End quote ---

Thank you for making my case.
enot:
I drew a diagram of the power supply (new type, Batch202207)
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