The Headache's and Hallelujah's of Pinball Repair

modessitt

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There is nothing more frustrating than having a weird, hard-to-find, and sometimes intermittent issue that makes you want to just smash the damn thing into a million pieces and mail them individually back to the manufacturer. And there is nothing more satisfying than finally figuring it out and fixing it.

We brought in a The Shadow for repair. Sound amps were blown and the pinball was fairly dirty. Fixed the sound board, cleaned and waxed, put in new topside bulbs and rubbers, fixed a misadjusted switch on the VUK to the miniplayfield, and played some games on it. Everything was playing great.

I noticed some underplayfield lights were out, so I lifted the playfield and changed them out. Put the playfield back down, went to start a game - and it wouldn't start! Just sitting there in attract mode. I put it into switch test and verified the Start button was working, then checked my fuses. F116 (12v Secondary) fuse was bad. Put in a new one and it blew right away again. Eventually I was able to determine that if I left J118 on the driver board off, the fuse wouldn't blow. This inidicated that my issue was definitely not on the board, and was related to my motors or optos.

At some point, we figured out that the fuse would not blow if the playfield was up on it's stands, but would blow at the point that it was almost all the way back down. We spent a full day going over wire harnesses, checking all the wiring around the hinges or the edges of the playfield for pinches or breaks. A couple times we thought we could smell something burning, but couldn't find anything burnt.

Well, then it started not blowing the fuse with the playfield down. We could start and play games, but then it would suddenly blow the fuse perhaps 2 or 3 games in. We were ready to beat the crap out of it at this point.

Today - we decided to up the amperage of the fuse a little to see if we could get whatever was giving us the burning smell to give us an indicator. We finally tracked it down to a diode on the little opto board mounted under the playfield near the start button. While it looked okay physically, one of the pads was burnt and it crumbled into pieces as I took it out. I replaced it, checked for other bad parts, and put it back in the game.

As that opto board only does the opto's for the ball trough, left ramp, right ramp, and center. We plugged the connectors in one at a time while checking the temperature of the diode. When we got to the connector for the left ramp entry opto, the diode started getting really hot. A quick check of that opto assembly showed that one of the wires had rubbed a small spot thru the insulation and was grounding to the left ramp. We pulled the entire thing out, replaced the wire, put heatshrink tubing over the entire wire assembly to cushion it from happening again, put it all back together - and everything is great now!

Apparently, the strain of the wiring harness when the playfield down, or the wiggling of the wire during play, was causing it to ground intermittently. The cut small enough that it was not easily seen, but it was all the way through.

Feels good to have it done finally, but hate that it took so long to find. But that's pinballs....
 
Congrats on finding it! I had a similiar issue on my D&D pin. A stupid poper ground wire was rubbing against a bracket and intermittently causing the popper to pop and blow the bulb inside. Took a while to find!

Game would play great for 10-12 games, then poof, flash of light as the bulb gave up its life and the popper would go off.
 
7 out of 10 doctors say, intermittent electrical problems are THE leading cause of high blood pressure in pinball repair persons
 
Very peculiar problems on that one there.
I have heard the shadow is a darn good pinball for such an odd ball license.
 
A couple of my favorites that took a while to find:

A brand new Road Kings that blew the solenoid fuse at odd intervals, sometimes weeks apart. You could play it all day without a problem, then the next day, poof. Finally found one of the pop bumper coils had been manufactured with the windings rotated 90 degrees to the base, causing an intermittent short in the wires leading to the solder pads.

A Time Zone with the same basic problem that started weeks after a broken wire rail had been replaced. Finally found that the legs of the new part were just a fraction longer than the old one, allowing one of them to sometimes short out a bulb socket under the playfield.

Can't say I got a lot of satisfaction out of solving either one, more like I just wanted to beat the crap out of whoever made the parts. Hours and hours of time spent driving to these locations and looking for the problem, not to mention the flak from the location owner and customers. This was back in the days when business was good and I didn't have a spare machine sitting around to swap out, plus I was still pretty new to the business and didn't know a lot of the shortcuts to troubleshooting. I finally found both problems by beating on the playfield with my hand until the fuse blew and narrowing it down to a small area.
 
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