HP-25 Co-luminous segments

[Tom Flatterhand]

In the repair book I could see in the wiring diagram that the wires are actually connected like i has written in this thread. :-) So there is definitely the possibility of influence. But probably I am on a wrong track.

I did not want to be smarter with my guesses in any case than the established experts here. Just to show that I am dealing with my problem myself. As a beginner in the HP calculator world this could not lead far of course. :-)

I am very happy about the good helps, but I can't always use them completely, because I have only one measuring line for my old scopemeter and also not enough crocodile clips. In addition, it did not start this morning at all, because it was for days without power supply connection and therefore probably the battery extremely emptied. I already thought it was broken. After meanwhile about 3 hours of charging, however, at least some power-on relay inside clicks again. Only the backlight is still off. But that was also in the past and therefore I'm in good spirits that it will fully work again today during the day.

The ROM0 is probably U1 from the location plan in figure 4-7 of the repair manual. According to the layout plan, the HP-34C is built a bit different than the HP-25. At least there seem to be more IC's on the bottom of the board than on the HP-25.

I will of course keep you (Tony) and the other readers informed...

Thomas