I have just built the K8115 Component Tester.
However, if I click the “Test” button, the LCD will light, but as soon as I release the button, everything goes off again.
I have tested the main board by looking at the +5V on pin 7 of the Atmega - but it turns out this is briefly just about 3.3V as long as I keep the button pressed, but drops to 0 as soon as I release it.
Further investigation of the VR2 (where the +5V is supposed to come from) shows that the input to the VR2 is already below +5V, so of course the output is too.
I take it the input to VR2, Vbat, comes from the collector of T1, and should be above 5V (the spec of VR2 suggests +7V) - but this is certainly not the case (when the button is pressed).
This is where I don’t know how to progress. Is T1 broken? Am I correct in thinking the collector should be >>+5V when the test button is pressed?
Any other things I should test?