K8115 does not work!

I have the exact same problem as many others reported. K8115 was carefully assembled and the only sign of life is the backlight. All voltages are measured and found OK!
I have read that a bad quality chip can be the problem. What can be done?
Thanks Cdr_51

Hello Cdr_51

The most common reason that there is no text on the display, only backlight is active, is a defective chip IC1 => CD4050.

We had a bad CD4050 delivery during a production batch.

To get it working replace IC1 CD4050.

If desired, we can send a CD4050 to You by post.
Create (open) a new ticket for this on our customer care service platform: Customer Care Velleman.
At this way, We can help You faster to solve this problem.

Best regards,
Velleman Support

Hello VEL450,
Thanks for your info.
I requested a new CD4050 Chip thru the Customer Care of Velleman.
Hope it will work out.!
Best Regards cdr_51

Hello VEL450/Velleman Team,
I have received your replacement CD4050 IC and tested the kit with this IC .
Unfortunately it turns out that this replacement IC does not solve the problem.
The assembled K8115 kit does work correctly with a power supply voltage between 6 en 7 Volt. Above 7V the text of the measured results do not show up anymore on the Display.
After measuring the varous output signals at 6.5V(Display OK!) and 9.5V( No Display !) from the 4050 IC I noticed that at 9V Supply Voltage these signals, which are also driving the Display, were still available but did not produce any text on the Display.
My conclusion so far is that the Display in some way cannot handle these (stronger?, overload?) signals when using the 9V battery supply voltage. Therefore it would be good to receive a copy of the datasheet and Model number of the 30pins 128x64 Display provided.
I hope you can confirm my observation and that we can find a final solution for this problem.
I would like to see that this component tester also works with a fresh new 9V battery as was intended.
Your support is highly appreciated,
met vriendelijke groet,
C. Drayer

Hello Cdr_51

See below the circuit diagram of LCD.

But I think it’s best to bring the K8115 back to your store where purschased, for a RMA REQUEST.


Best regards,
Velleman Support

Thanks for your schematic. I had it traced myself quite a way already.
My request was for the 128x64 Dispaly Model nr. , Manufacturer and or datasheet.

After somemore evaluation I will certainly consider returning the assembled K8115 back to Velleman via the Elektor Store where the kit was purchjased.

Hope to soon receive some additional technical Display data from you,

Best Regards,

I ask the product developer for the Datasheet of the LCD.

But anyway, the Component Tester K8115 must work with a new battery 9V.
When CD4050 has been replaced, and still no text on display, there may still be a problem with the display itself and / or CPU. In that case it’s best to return the product to the store where it was purchased for an RMA request.

Best regards,
Velleman Support

Dear Support Team,

I just receive information that other customers who also had exactly the same problemwith this K8115 kit, have solved it by using a 74HC4050N chip ( instead of a CD4050 chip)

I would appreciate if you can sent me such a chip to get my K8115 kit working properly at 9Volt.

Best Reagrds

C Drayer