Tuesday, April 13, 2010

Field Lamps!

I went to Pinball Life and purchased new replacement LEDs for my field lights.  They're colored and that color makes a big difference with some inserts.  The Reds are OK, the Oranges are better, and the Blue REALLY makes a difference.  I'll post some before and after pictures soon.  This article isn't about LEDs though.  It's about my blue 4K lamp that wouldn't light.

This wasn't a simple bulb replacement.  There was something more complicated that was wrong with this lamp.  I tried some tricks like giving the socket a little tweak, flicking it while it should be flashing, things like that, but none of those things worked.

I decided to test the voltage while the system was in lamp test mode.  This flashes all of the lamps so proper testing can be done.

I can't recommend this as the exact way to troubleshoot this problem.  It's just the way I approached the problem and it worked out.  With the bulbs flashing, I tested the voltage on a working lamp.  My multimeter is not fast enough to lock into a voltage with the bulbs flashing, but I thought that I might get enough information to eliminate wiring as the problem.

The good bulb readings rattled around and as predicted, never locked on a number.  The highest number I would see was 3 volts.  I tested the bad bulb and found that it got a reading, but never above 1.

I tested the one other component on the light socket and that was the diode.

EDIT: (From a chat session)
chad: oh, your blog about the bad light fix... you need to highlight the fact that the diode looked perfectly good visually... so most people would not suspect that the diode was bad.

Testing the known good bulb without removing the Diode from the circuit.

This is a good reading.  I did the same test on the other diode and got this no matter which polarity I tested.

Now, I've read that a diode in circuit can give odd readings, so I decided to clip one lead and test again.  At this point it should be noted that the bulb socket was buried and it was time to unscrew it from the playfield to get proper access.

I dug it out and clipped one lead:


All of these tests yielded the same result.  .0L

So it was time to solder a new diode in place.  Here is the new diode!

After all of this, what was the result?


I was very happy.  This was the first time I didn't need to consult a guide to figure out what the problem was.  It was only one light and the solution wasn't that complex, but it felt good to fix something based solely on my own, if misguided, troubleshooting.

Here's the thing, lets get serious here for a minute.  I have a couple of years of High School electronics under my belt.  But like most people's high school Spanish, I  can barely remember any of it.  It's coming back to me as I go and really, I'm loving it all.  It's not that hard to follow a schematic and to test every component of a circuit to see if it's in spec.

I guess that's the first point.  No one should be afraid to try this.  I'm doing some of these things and I would love to say it's because I know what I'm doing, but really it's just a few tool skills and following instructions.

This blog is a work log and it's supposed to be an adventure with a guy who is learning as he goes, I guess this digression is to let any readers I might have know that I'm aware of that.  I have no delusions of expertise.  I hope someone learns from what I'm doing here not because I'm an authority but because I wasn't afraid to try while others were watching to see what happened.

Now, donde esta mi cafe con leche?

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