Ari [APz] Sovijärvi18h ago

People often diss Doctor Who's mini playfield lift mechanism, mine's pushing 26 years after the initial rebuild and I've never had any issues with that part of it.

Just below the first stage however sits a row of 5 weird looking targets. They're optical, meaning each of them has a IR LED + phototransistor pair, which gets interrupted by the target when it gets whacked by a ball. While the design is very robust, every now and then one of the LEDs gives up the ghost.

The targets are in pretty hard to reach place, which requires pulling the mini playfield out of the game and disassembling the whole front part. When this happens, it gets a full service of regreasing the rails and the gearbox.

Also seen here is my go-to trick for diagnosing optos: just look at them through a digital camera. They always seem to emit at least some visible light even with the modern phones having an IR filter.

#pinball #repair #pinrepair #retrotech

Show threadAri [APz] Sovijärvi

I've been observing this bracket getting more and more bent over the years. The lower part is so crooked the target shafts are almost hitting the LEDs and phototransistors. I've also asked about replacement for this part as it does take quite a beating from direct ball this.

It's not mechanically complex, I might be able to throw something together in CAD. Printing it would require a pretty awkward orientation to prevent it from cracking from the layer seams.

#repair #retrotech

Apr 14 at 12:25amWeb
Show threadAri [APz] Sovijärvi17h ago

After some head scratching, I found couple of spots where I could make it thicker than the original while keeping it drop-in compatible.

The shape's a bit tricky as I can't have layer seams across the weakest part, which means it has to be printed on its side. And preferably of something really durable like PA. Or maybe ASA will work too. I'll have to experiment on this.

#freecad