DSO not working properly, strange errors.

[Bug7734]

Hello,
I have problems with getting my DSO Shell to work properly.

My voltages:
V1 = -0.7mV
V2 = 0.4mV
V3 = 1.3mV
V4 = 1525mV
V5 = -1023mV
V6 = -2.77V
AV- = -6.05V
AV+ = 7.05V
AIN = 0V
V- = -7.74V

The R1 resistor were broken when received, so I had to replace it with four smaller ones to get the right value.

The PCB board for the encoder was defect, the signal when the button is pressed is not connected properly.
I have to use a jumperwire to access the test signal.

The C3 and C5 capacitors are not working as well, but that could be my fault.
Maybe I can order those broken parts?

Regardless of that, I get strange results from my DSO. I wanted to make a video but that is not so easy, because sometimes I switch it on and it seems to work and only the voltages displayed are just wrong, sometimes it's drawing only noisy lines and other times the waves are just "moving in hyperspeed" over the screen. I have even times the square waves transforms into everything but squares. And the voltage displayed is always wrong, sometimes negativ when it should be positiv and changing values when changing some parameters on the DSO.

I replaced the C3 and C5 capacitors with fixed 22pF capacitors, so I could test it.

I hope someone can help me. Thank you.

[jye1]

Can you show what signal you connected and the display by photos? If you see waveform jumping randomly pay attention to the ground connection of probe.

The issue that you found 0.1V could not be enabled by the push button of encoder might be due to the large DC on test signal. Please see the FAQ at the top of this forum.

[Bug7734]

First of all, thanks for your answer.
I checked and resoldered the ground of the probe.
Now I have a "nice" test signal displayed.

But I still need new capacitors (C3 and C5).
So please tell me how I can order them and a new R1 resistor.

I don't get the issue of the encoder. If I connect the pins with a jumper cable instead of pushing the encoder I can change the test signal and switch it on and off.

But the main issue is the problem with the voltage displayed on the screen, if I change the voltage resolution from 50mV to 20V the voltage displayed changes extremly between 0V displayed and by 20V to nearly 20V displayed.
The source was a 6.5V battery. Or is this normal and voltage display is a more "nice to have" feature?

[jye1]

For R1 replacement please contact JYE Tech at jyetech@gmail.com.

Please see the tips (it has been updated) at top of this forum for calibrating C5 and C3.

6.5V is too low for the analog circuit. Can you test with a different power supply?

[Bug7734]

Okay,
I will give the idea with the wires as capacitor a try.
In the meantime I uploaded a video showing my problem.

I used now a 12.3V constant DC source.

https://youtu.be/DRFnK0eiW_E

[DanilinSA]

You should not use the supply voltage > 10V.

U5 (ILC7660):

1.5V to 10.0V Operating Supply Voltage Range

[Bug7734]

No, I measured a 12.3V source. The supply voltage is exact 9V.

[boo]

No, I measured a 12.3V source. The supply voltage is exact 9V.

9V DC - into the DSO. What the 12.3V? This makes no sense.
Where are you measuring the 12.3V and why?

[Bug7734]

Why does it make no sense? The DSO has a power source of 9V and the alligator cables are connected to a 12.3V battery to test the voltage readings.

[boo]

Why does it make no sense? The DSO has a power source of 9V and the alligator cables are connected to a 12.3V battery to test the voltage readings.

Now it is clear. It did not make sense because you said "I used now a 12.3V constant DC source" and we were talking about power requirements of the DSO, which is <10V. OK, so you're powering the DSO with 9V exactly, and you're measuring a 12.3V target. I don't know what your problem might be - I just did a check on a 9V battery with my DSO Shell, and it worked OK. You do have the input switch set to "DC", I assume.