James’ Blog

Fire in the Disco

Posted on February 2nd, 2007 by James.
Categories: Pinball.

The special effects on my pinball reached new heights today as some started pouring out from under my Klingon bird of prey!

After a split second of mild heart attack I quickly reached under the killed the power then popped the hood to check out the damage.

The divertor which sends the balls to the left cannon (“Under Divertor Bottom”) somehow overheated and melted. You can see in the insert that the center is full of melted plastic from the tube which normally lets the metal rod slide through. Not good! Luckily it didn’t catch fire.

Interestingly, the 7A fuse which I recently changed blew. So… great that the fuse blew, because that probably stopped the solenoid igniting.. but is it just a freaky coincidence that that same 7A fuse blew before? I have two ideas:

1. This solenoid being faulty was the reason the 7A fuse blew in the first place.
2. One of my bridge rectifiers is knackered. (Probably BR3 for those in the know;-)).

This solenoid runs off 50volts DC, created from the AC supply using BR3.. which I now know for sure, because I just checked in the manual!

I have to go off track for just a sec and point out how totally awesome the STTNG manual is. You can find out EVERYTHING from this baby. For instance.. with this solenoid thing.. First I go to the solenoid-flasher table on page 3-5 and find the solenoid. From my picture I can see it’s got a White-Black wire and a Violet-Green wire. I can identify it just by that, but it also has the name in there. That table tells me it’s using pins J107-1 and J4-2. Then I turn to the solenoid wiring on page 3-8 and I can see exactly what components it goes through. One of which is the all important AC to DC converter, Mr BR3 the Bridge Rectifier!

So my theory;

1. If the solenoid is knackered then it would go wobbly and blow the fuse.. I change the fuse. The solenoid is still knackered so it melts a bit and blows the fuse again.
2. The Bridge Rectifier is knackered. So instead of giving the solenoid a nice 50v DC current, it pops it with a little unregulated AC. Instead of the solenoid generating a nice magnetic field to convert it’s energy into motion, it instead would just vibrate the metal rod inside it, generating heat via friction, or alternatively, it would just get really hot, like a regular household AC light bulb does, which is essentially just a wire with AC going through it.

Since both are just a feasible as the other, I think I’m going to err on the side of caution and replace the Bridge Rectifier just in case. The solenoid is getting changed anyway, since this one is a charred mass of plastic in the middle.

You can look forward to some interesting pictures of my power driver board getting ripped apart soon, for some fun soldering work! 🙂

Alternative titles for this post:

• Danger! Danger! High Voltage!
• Disco Inferno
• Merry-go-round break down
• Come on baby light my fire
• Burn baby burn
• Firestarter

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