JYE Tech DSO112A Schematic

[ondras12345]

Hi,
Does anyone have a schematic for the DSO112A chinese digital oscilloscope? I found this thread on their forum https://jyetech.com/forum/viewtopic.php?f=17&t=358, but the files seem to be corrupted.
I need the documentation because it measures bad values for the voltage.

Real voltage	Shown value
1 V	1.08 V
2 V	2.28 V
3 V	3.48 V
4 V	4.64 V
5 V	5.84 V

That is with 1V/div. The other ranges are the same, except for 5V/div which shows 11.4 V for 5 V real (all the values seem to be multiplied by 2.3 on this range). I don't mind the error on the other ranges that much, but it'd like to fix the 5V/div range.
I'm suspecting there might be some resistors swapped on the board, as it was reported here https://jyetech.com/forum/viewtopic.php?f=17&t=1850.

There are no trimmers inside the oscilloscope, just two trimmer capacitors (C64 and C24). I think they are used to compensate the attenuator, so maybe there's no way to calibrate the attenuation rate.

[paulca]

Vague recall there might be a calibration in software.  Might be wrong though.

[ondras12345]

If it uses software calibration, there's no data available on that. The user manual describes the communication protocol for USB scope mode, firmware update procedure, etc., but there isn't anything about sw calibration.

[shakalnokturn]

Gain could be corrected in software, I'd expect the hardware attenuation is built around the 4051, 4053 though.
Is offset right?

[ondras12345]

Gain could be corrected in software, I'd expect the hardware attenuation is built around the 4051, 4053 though.
Is offset right?

5V real at 2V/div: 6.00V when positive voltage is applied, -5.76V when negative voltage is applied.
5V real at 5V/div (the bad range): 12.00V positive, -11.6V negative

I'm really suspecting some resistors might be swapped. It was reported before and it would explain the values getting multiplied.

[glentek]

Old topic, but if anyone has one of these scopes and the 5V range is reading double, two resistors are swapped - shown in photo.
They are part of the divider chain for x4, and x10. One on left should be 49.9, and one on right 150.