Saturday, March 27, 2010

Better to be good or lucky?

Today I went to the Midwest Gaming Classic in Brookfield Wisconsin which is just outside Milwaukee and less than 2 hours from my house.  There was a lot to look at and maybe once my head has stopped spinning I will post about it.

This is a work journal though and the work I did was on my display.  While up at the classic I dug through a "junk" box and found this:

It's a 7 digit numeric glass display from a Williams game older than my F-14.  I thought that since it was Williams and I'm sure they wouldn't re-invent the wheel, this might be the same display as is used in my F-14.  I paid $10 for this.  Not knowing if it worked or not I probably should have paid $5.  I'm just not savvy enough yet.

What I would need to do is unsolder the display from this board, unsolder my bad display from my board, then solder this "new" one in place.  I had no real concrete evidence that it was the glass display on my board that was actually the problem.  I checked the voltages on the pins of my working and non working displays and found them both to be the same. 

I figured that if the voltages are making it to the display that if it was good, it would do something.  But it was black.  The downside of my gamble was that I could go through all of this work to put a bad display in place of another bad display.  I could have tested the display in another pinball machine, but I don't have one that works.

Here is a pictorial of the process:

This is a desoldering tool.  I will use this to heat the solder on each connection, then release the suction ball and the liquid solder will be sucked off the board and into the tool.  Here's a tip:  Before you squeeze the ball again to prepare for the next "suck", make sure it's over a paper towel or something and not over the board -- you'll shoot molten solder back out of the tube onto the board!

On the left you see where I've unsoldered the pins (is it unsoldered or desoldered?)   The pins are pretty big so this was pretty easy to do.

Now that the pins are all unsoldered, I need to remove the display from the board.  You can see it's attached with two sided foam tape.  I used a razor blade from a utility knife (no knife, just the blade) to separate them.  I was being carful to not cut myself while also cutting on the board side.  I was cutting on the board side because if damage was done I wanted it to be done to the board which I was going to throw away, not the glass I was re-using.


OK, Onto my board.  I have to repeat the same process on my board.

This is the F-14 board after the display was removed.  You can see that there is a lot of left over flux.  I used a toothbrush and a little acetone to clean the flux off the board.

Here is an "After" shot, much better!

Here the pins are all fed through the board.  The toothbrush isn't the only handy dental tool.  You can buy a set of dental picks really cheap from Harbor Freight tools.  This was key for getting all of those pins through the holes on the board.  before soldering, I "backed the pins out" a little bit.  I didn't want to solder that much pin, plus I thought I might need every bit of length of those pins on the display side.


So did it work???  Did my $10 gamble and 30 minutes of board work pay off?

It works!  There is a problem though.  The pins are just a HAIR shorter on this display than the current displays.  It's making it sit weird.  You can see it here.  Since I know it works, I'll cut the pins and use the pins from the bad display to extend the length enough to make it sit correctly.

I excitedly showed my wife and she said, "Uh, good."  and left the room.  I stood for a few minutes appreciating my work, a little disappointed by her reaction.  I found her and said, "I'm a little unsatisfied with the enthusiasm you showed for my victory."

"To be honest, I don't really understand what you were showing me",  she said.
"Well, I fixed a $200 board with a $10 junk part."

That's when she gave me the high five.

Now to fix this:

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