Thursday, August 19, 2010

Rock solid!

One of the toughest things about this hobby is dealing with the little things that are amiss with a game. My Asteroids Deluxe has always been a great playing machine, but the screen never really looked right. Asteroids Deluxe has a neat screen setup, where the picture you see is the combination of the vector monitor output and a blacklit 3D background. The two images are combined by a partially silvered first surface mirror. This mirror reflects some light (from the monitor) and transmits some light (from the fluorescing backdrop behind it). The problem with my screen is that you could see a dim white rectangle the full size of the monitor. There was no way to adjust this out.. and it totally killed the 3D background effect. You want to see ships and rocks floating in midair, not on a dim white screen that is interfering with your view of the cool 3D stuff!

My screen was also missing the blue 'gel' that goes in front of the monitor. That didn't bother me so much--I figured experiencing the game in white lines wasn't that much different than experiencing it in blue lines.

Then I got thinking about this a bit more. (For this next bit, you need to bear in mind that during my day job, I do a bit of spectroscopy, which deals with the interaction of light and matter.) What if it was the black light that was causing the screen to show up as a white box? As it turned out, the ultraviolet (UV) light from the black light was making its way through the partially silvered mirror, straight down to the picture tube. The UV was then causing some of the phosphorescent material on the tube (that is supposed to be lit up by the CRT electron beam only) to glow. As it turns out, air doesn't block UV very well. Glass (i.e. the mirror) doesn't block it very well either... but plastic, well, plastic is another story! Plastic is very good at blocking (absorbing) UV rays, and guess what the blue gel that is supposed to go on an Asteroids Deluxe monitor is made of.. You got it, plastic. With the blue gel in place, the UV from the black light does not have nearly as big an effect on the picture tube:

It's not perfect, but the effect is a heck of a lot better than it used to be!

Another small issue popped up what I was tinkering with the machine--intermittent power failures, accompanied by nasty audio buzzing, graphics flickering, and high scores getting wiped out. This machine has a (relatively) fresh big blue capacitor, a rebuit AR board, and a recapped/rebuilt monitor. Upon further investigation, it turned out that by jiggling the cables on the power brick, I was able to reproduce the effect. I figured it might be a bad molex connection on the brick, but the pins looked factory fresh. Things on the AR board looked great too--no loose pins or cold solder joints anywhere. Then I pulled on a few wires that were leading into the power brick (through the hole on top). These wires went to the (fresh) big blue... but they were the culprits! As it turned out, the end loops on the wires were loose where they were screwed on to the big blue. I had replaced that big blue a few years back, and apparently the replacement I got had screw holes that were a little bit too shallow for the factory screws that were used on the original big blue in this machine. The machine had worked fine for many years, but apparently the jostling the machine has seen over the years (including a coast to coast move!) had slowly loosened the wires. I pulled the screws and washers and cleaned them with a wire brush. Then I sourced a few more washers (to make up for the fact that the screws were a tad too long) and securely screwed the wires in place. The machine is now rock solid! The moral of the story--even if you know the big blue is good, check those connections! There are lots of wires going into and out of that capacitor, and they are all vital to smooth operation of your power supply.

One interesting side note is that these power issues wiped all of the high scores on this machine--high scores that were there when I bought the machine (I tend not to clear out high scores on my games). These scores were ridiculously high scores set by some guy named 'DAN'. DAN, I wanted to beat you the legit way, but it just wasn't in the cards. Now to *finally* put some scores of my own on there.

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