No readings on the display

Edukits EDU08
1

Hi there
I assembled the edu08 kit. The display works, but it does not show any measured values. Not even when I use the testpin. where could the mistake be?

2

Please check all the parts and solder joints of the input section between input connector and IC3.
Check the voltage on all pins of IC2.
The voltages should be about:
1: 1.6V
2: 0V
3: 0V
4: -5.2V
5: 0V
6: 0V
7: -1.6V
8: 6V

3

Hi.
I checked the Voltages of IC2. All is correct but no measure value. What can I do ?

5

Is there a horizontal trace seen in the middle of the screen when the oscilloscope is running?
Is there any random noise seen on the trace?
Is there any change seen on the trace when the red test lead is connected to the test pin?

Next tests:
Remove the display board and keep it disconnected during the next tests for easier access to the bottom board.

  1. Check the continuity of the test leads.

During the next tests you can use the black test lead as ground reference.

  1. Turn the oscilloscope on and check the DC voltage on the test pin.
    There should be about 1.65V.

  2. Check the voltage on pin 2 of IC3.
    There should be about 1.6V.

  3. Connect the red test lead to the test pin.
    Now the voltage on pin 2 of IC3 should be about 2.6V.

If not:

  1. Check the voltage on pins 1 and 3 of IC1.
    On both of these pins there should be about 0.4V.
6

Hi there.
All information up to the voltage at pin 2 of IC3 checked and okay.
But when I connect the red test lead to the test pin, there is no voltage.
Also no voltage on pin 1 and 3 of IC1.

7

And there is no change on the trace when the red test lead is connected to the test pin.

8

This may indicate that the red test lead is short circuited to ground.
Maybe there is a solder bridge between SK1 and GND.