Extending the Life of Pinball Alpha-Numeric Displays
January 10, 2018 Reading time: 2 minutes See Comments
The glass score display tubes used on most pinball machines have a limited life and will eventually "gas out". This is not only inconvenient it is now days hard to find replacements and they can be very expensive.
For this reason we should try to extend the life of our displays for as long as possible. Many of these displays run at high voltages of around +100V DC and -100V DC. This allows them to be nice and bright when the pinball is being used in an arcade, but these days many of these machines are now installed at home.
Reducing the voltage by just a small amount will give a dramatic increase in service life. In this example I will be changing the zener diodes on a Data East 520-5000-00 power supply board. By changing the 100 Volt 1 Watt 1N4764 zener diodes to 91 Volt 1 Watt 1N4763 diodes we will effectively reduce the voltages being delivered to the displays. On this particular board the diodes in question are D9 and D10.
You can see D9 and D10 highlighted in the image below. Before changing these the measured voltages were around ±103V DC, after swapping them for 1N4763 the voltages were reduced to ±95V DC. The difference in the display is barely noticeable.
It should be noted that if your display is already flickering or faded then it is probably already starting to fail. In this case changing to a lower voltage may actually make the symptoms worse or may cause it not to display at all. In this case either your board needs servicing or the displays need replacing. If you do replace the displays I highly recommend changing the diodes at the same time.
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Pinball #89 Globes too bright in Mini-Domes
January 7, 2018 Reading time: 2 minutes See Comments
Globe brightness in a pinball machine tends to be a personal preference and also depends on where the machine is being used. Most pinball machines were designed to be used in arcades that are usually well lit. When a pinball machine is used at home the lighting can be very different. The mini-domes arranged above the playfield on the Data East Simpsons machine were way too bright for my liking even with the standard #89 incandescent globes. When replaced with #89 LEDs they were slightly brighter again. There was some improvement when the LEDs matched the same colour as the domes (rather the white) but still too bright.
My solution was to use some sort or filter/diffuser inside the dome. I ended up using the casings from old fluorescent starters. By cutting them down slightly with a hacksaw they fit snugly over the LED. Then with the dome re-installed the light is nicely diffused and much easier on the eyes.
Here are a few photos to illustrate the process..
