Component tester kit K8115

I assembled the kit but the display does not show data when the button is pressed twice while calibrating and all probes connected to each other. It only lights up for a few seconds and then goes out again.
Is there a way to test the display to find out whether it has been soldered correctly?
or

Update: VR3 pin 1 should give 3V3 but I measure 4V39. Anyone had the same problem?
Is VR3 defective? Did the overvoltage blow my LCD?

Hello,

First we have answerd this topic on Your posted Customer Care Ticket. and topic above.
And today we have sended the requested parts to You by post.

When you receive the parts, first to do is replace the IC1 4050.
In the most cases this will solve the problem of no text on LCD.

Due wrong delivered batch of CD4050. Our apologies.

Best regards,
Velleman Support

Hello guys,
my feeling is, that I have the same problem.
After assembling all parts I did the first test - if fails - only the background light of the display was on.
After about 25 seconds the display got off, however turned on again by pressing the button.
Again after about 25 seconds the display got off. (see attachment)
So I checked the soldering and parts - everything ok.
Next I checked the voltage - however without LCD PCB.
The output of VR3 had 4.4V while the input was about 5V - originally it should be 3.3V
Based on information of the forum


I removed IC1 (CD4050) - in this case the output of VR3 had 3.3V.
So I assume that I probably have also a problem with wrong or damaged CD4050.
Based on the information of this forum I opened a ticket, however they closed the issue
explaining, that I should search for help in this forum.
It seems that the Velleman product support dont’t care about customer issues.
How should I proceed now?
Any suggestions?

I reopened the ticket and requested a new IC1 and VR3. Copied the solved forum item which had the same problem. They’ve sent me a new IC1 and VR3.
I replaced de IC1 but still the same problem. I did not get to check the VR3 yet.