EDU09 output offset

#1

Hello

I recently bought the EDU09 Oscilloscope kit from Velleman. The calibration process works fine, but there seems to be a DC output offset.

When connecting a 10V DC source, the oscilloscope measures a voltage just below 5V. Also, when connecting the probes to a 1.5V battery, to perform the advanced calibration, I was only able to adjust the DC mean between -0.2V and 0.2V.

Voltages on IC2 and IC3 correspond to voltages already mentioned on the forum.

Can someone help me with this issue.

Thanks in advance.

#2

Please check the test leads for continuity.
It seems there may be missing or bad connection.

Please test: Is this (-0.2V and 0.2V) the result on 0.5V/div range if no battery is connected and the test leads are connected together?

#3

Thank you for your response.

The issue was a bad solder between R28 and R24, which resulted in an excessive voltage at pin 1 of IC1. This is solved now and the EDU09 works perfectly.

1 Like
#4

No problem. Glad you resolved the issue.