Planning Poker

January 30, 2007 at 11:58 pm

We’ve been spending some time trying to figure out what our team can get accomplished in the next 6 months or so. We have a feature list that we’re considering, and we need to apply some numbers to it.

So, I decided to try using Planning Poker. I made up some index cards with values in dev-weeks, in the values 1/4, 1/2, 1, 2, and 4.

It has taken a fair amount of time to get through this process, but the numbers we got are a lot better than we would get with other methods, and more importantly, the dev team has a much better idea about what and how they’ll be building whatever we are building (I apologize for being evasive, but it’s a bit of an organizational disease right now).

Note that I’m not recommending all-up estimating. In general, I don’t think you should be costing more than a month or so worth of work at a time, as the quality of the estimates won’t be great. In this case, we needed a go/no-go number, and the estimates that we got were good enough.

Hardware debugging – fixin’ the Meteor

January 23, 2007 at 8:34 pm

Last fall, one of my friends accepted a job offer back east and needed to put his possessions on a diet. He called me up, and asked me if I wanted to take his Meteor.

Meteor, of course, being a pinball machine manufactured by Stern way back in 1979.

I drove to his house, picked up the machine (which had mysteriously gone from working to not working, apparently in the time it took me to drive across town), secured it in the back of the truck, and then took it up to the cabin, where I introduced it to Bad Cats.

And then it sunk in. When I only had two machines – one per house – I could deny it, but adding the third made it obvious.

I was a collector. Especially since the new machine didn’t work.

A bit of debugging found the first fault – there was a break in where the line cord was attached (a substandard solder joint). A quick wire nut fix (no soldering iron with me), and the machine woke up. More or less – there were a few playing issues, but it mostly just needed some light bulbs. A whole-lotta light bulbs (note to readers – foreshadowing!!!)

So, I headed on over to Pinball Repair Section of Marvin’s Marvelous Mechanical Museum for a repair guide, one of the sources of specialized information that makes the internet great.

Which leads to a brief aside. The Meteor is made by Stern, but the repair guide you need is for Bally machines.

When Stern started building machines, they needed a control system to use. They could have developed one from scratch, but that takes a lot of time and money. You could license it from another manufacturer, if they would do that, but they won’t because they don’t want the competition. So, Stern just stole the design, Bally sued, won, and got awarded… a license fee per machine. The same thing happened a few years later after Data East stole the design of the Williams control system.

I upgraded the woefully underdesigned power supply (which was apparently designed by the guys who took electronics with me in high school back in 1976), replaced all the bulbs (about 60 of them), turned on the machine and… None of the bulbs worked.

So, I re-replaced the bulbs, and then the fuse that supplies the power to the solenoids (bumpers, slingshots, drop target reset) started blowing. And the bulbs still didn’t work.

I checked a bunch of things, but couldn’t figure out what was going on.

Then I got lucky, like the program that finally crashes where the bug reports says it does. One of the power resistors on the power supply started smoking.

Generally, that sort of behavior isn’t the kind of thing you’d prefer from an electrical device, since you risk losing the Magic Smoke. But in this case it was great. I grabbed my voltmeter, put it on the resistor, and found 47 volts. Which was great, because it told me what was happening.

There is a 47 volt supply that drives the solenoids, but I was reading that voltage on the 6 volt supply to the lights. That was enough to blow the fuse, and it was also enough to make the bulbs *really bright* for a very short period of time.

It only took about 5 minutes to find a wiring harness section that was really tight, and the voltage came back to normal. Now I just need to replace all 60 bulbs again…