ATARI MIDDLE EARTH DISPLAY HELP

[ddstoys]

Ive finally got around to looking at the display.   All the voltages are correct upto the boards and the credit section mostly works but as soon as i plug the score display pcb in drags to voltage down to about 20v instead of the 90v when unplugged.    Any thoughts on what might be dragging down the voltage?   Im thinking it might be the capacitors and the zener diode for the 5v section????

[Pinball Fixers]

If the Score Panel PCB is pulling the 90V line down to 20V, then it is most likely something to do with the Score Panel PCB or the Displays themselves.
I highly doubt that anything in the 5V section will be causing this.

I'll have a look through the schematics either later tonight or sometime next week and get back to you on what I think it might be...

[Pinball Fixers]

I've just had a good look at the circuit, and I was mistaken about the +5V section... I didn't realise it was derived from the +90V rail.

OK, the parts below make up the +5V section:

C3 - 10uF 25V
C4 - 0.1uF
C5 - 10uF 100V
R105 - 22K
R106 - 47K
R114 - 33K
Q53 - MPSA42

Also, you'll need to check the transistors and resistors that control the display glass anodes:

Q46 -> Q52 - MPSA92
Q54 -> Q60 - MPSA42
R91 -> R97 - 10K
R98 -> R104 - 120R
R107 -> R113 - 10K

If all these test/measure OK, then you may have a problem with one of the display glasses themselves.