Hello,
Some time ago I purchased a Velleman K8115, Component Tester kit.
I have only just assembled it and found that it does not work with a 9v battery, i.e. only the backlight comes on but nothing is displayed on the screen.
As you wrote that you had the same problem, you tried it under other supply voltages and saw normal operation under 6.5 V instead of 9. So I plugged in a large 6 V battery actually giving 6.4 and my tester is working fine! However, oddly the display either shows “Bat. 7.3V OK”, or “Bat. 7.3V weak”, while the tester is supposed to work under 9V. I’m going to get a 7.2V rechargeable battery (same size as the 9V batteries) and see if it works.
I would therefore like to thank you for your very useful information which allowed me to solve this problem, because I would never have thought that the failure was due to a bad voltage. Especially since having little experience in this type of assembly, I thought I had done the tiny welds of the LCD screen incorrectly!
I will be contacting Velleman to ask if they have a solution to get the tester to work properly with a 9V battery, which would be much more convenient than fiddling with connections with other battery models or rechargeable batteries.
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