Thanks for the measurements. It looks like the trace going to the Intel microcontroller (P2.7 pin) is low so all the voltage is being dropped across one resistor. Not sure why this line is low. The only suggestion I have is to measure Vcc going to the Intel microcontroller to see if this voltage level looks okay. As long as this line from the microcontroller is pulled low T011 and ZTX751 transistors are not going to turn on so no 12V pullup voltage for the switches. I'm just hoping the Intel part isn't damage and it's a power problem or some other input to this chip that's repairable. It's possible the bad output of the 2950A voltage regulator could be impacting the controller but I just don't know. The output of the VR goes to the dual comparator LM2903 chip but from there I can't follow all the traces. Could use Bob's input on all this one. Hopefully replacing the 2950A regulator and restoring the 5V output will help.Hi Swany! I took the measurements and results are not what you expected, except one. Results were taken in normal state, nothing pressed, those are in yellow color and when S84 is pressed in red color.
I ordered 2950A CZ 5.0, it should arrive in two days, then I can replace that.
View attachment 2612710
With the microcontroller line low the voltage level needed to turn on T011 isn't present so the 751 transistor is also not conducting and no 12V to pullups.