Component tester (K8115) kit’s screen only shows backlight after a new IC1 CD4050

I had read here earlier that this error would be due to the IC1 CD4050, however I got a new one today and put it on the board. The problem is still not resolved; I still only get to see the blacklight. I then reheated all the soldering tips (so that the solder might adhere better) and tested the connections with a continuity measurement. Nothing will help.

I have measured the components according to the schematic and conclude that it is not the CD4050, this IC works fine; However, I do not know if the output voltage of the VR3 (LP2950-33LPE3) should be exactly 3.3V? I measure a voltage of 4.3V. The input voltage is indeed 5V.

Hello MrBijnens,
I had same problem with only backlight on. Very kind people from Velleman support team sent me a new chip - CD74HC4050E. Chip without HC did nor work for me, I have tried a lot of them. So find 74HC4050 and try - it worked for me!

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Dear MrBijnens,

Since this concerns a technical defect either IC1 CD4050 in most cases, or sometimes CPU U1 (Atmega328).

In this case it’s better to report this problem on Our Service Ticket System, so we can send the replacement parts. You can Open a new ticket via this link:

At this way We can help You faster to solve this problem.

Best regards,
Velleman Support

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Hey RadoS57RZ,

You’re right; the 74HC4050N is the solution to my problem. Thank you very much for helping me out. If I can ever help you with anything I’d like to hear from you :slight_smile: