Williams "Black Knight" pinball restoration.
Factory variations, and Williams add-on's (Please forgive my little notes that will eventually be replaced with photos)
Black Knight was one of those Special machines, which don't come around too often, that saw a huge production run and a long lifespan in arcades. To say this game was popular is an understatement... In the early 1980's it dominated pinball. Because of this extended production run, and because of the sheer number of machines out there, it saw a number of improvments from Williams during its support cycle. Some of these were installed in the factory, while others came as add-on kits and components that were installed later. On this page I'm going to try and compile as much information about these changes as I can. Note that this is very much at the early stage of this project, and I have a lot of information to add in. I've also got a lot of research to do. There are some features I am particularly interested in hearing from you guys about, so please e-mail me if you have more info to provide on ANY of these topics. However, one thing I am not going to cover at this time is variations in the circuit boards. There were a number of changes to the driver and CPU boards during the System 7 lifespan, but that is outside of what I want to do here. I also haven't done anything yet to document what was different in the follow-up run of the Black Knight "Limited Edition" machines. I may do that at some point, and would love to get info regarding that, but since I have no access to any of these machines yet I can't put anything here.
One of the most commonly known changes, which took place in the factory during production, was the changeover from the System 6 to the System 7 power supply. This a big improvement and a big problem to the design. The big improvement was changing over to a full-wave rectifier bridge for the 12v and 5v DC circuits. This is a much more reliable design, while also providing smoother DC power. Unfortunately, the GI lighting circuit was also moved to the power supply board, which causes all machines with this design to suffer from burned connectors. Why they opted to put a 15amp lighting circuit through a 12amp connector, I don't know.
System 6 style power supply. Photo curtosy of Marty at Melbourne Pinball Restorations	System 7 style power supply.
Now, this is only a suspected change that I'd LOVE to see more conclusive evidence. But my suspicion is, which there is playfield evidence of, is that there was additional GI lighting originally included on the playfield. There are spots that would make sense to have lights installed under two of the plastics on the right side, but there are no lights present. I have seen photos that suggest lighting, but none that I can verify weren't added in by owners at some point. I would LOVE to see photos of these areas if you have one with original wiring and lights.
	Right side plastic will go here.
A lesser known issue that popped up during production by Williams in this era was incorrectly assembled leaf switches. Williams spent the extra money to have gold plated contacts made, but the contractor goofed and assembled the leafs backwards. The result is that the rivets, instead of the expensive gold contacts, were what actually made contact during switching. Apparently this showed up most in places that the balls sit in for extended periods, such as the shooter trough and multiball trough. To address this, Williams offered a retrofit set that converted these six leaf switches to microswitches. It included all the brackets, wireforms and switches needed. My Black Knight has these kits installed, and I even have the original isntallation instructions for them. I've scanned these instructions, which are available at the link below, or also at IPDB.  This changeover became standard on the later Limited Edition machines built in 1981. I also have a copy of the original instructions for making this conversion, which includes the part numbers and diagrams, which covers both trough conversions.  Here's the PDF link for you if you're interested. Microswitch Conversion Kit Instructions.
Shooter trough photo w/ leaf switches will go here	multiball trough photo w/leaf switches will go here
Shooter Trough with the microswitches Photo curtosy of Marty at Melbourne Pinball Restorations	multiball trough photo w/kit will go here
Here's another add-on that Williams offered to address a design flaw, which manifested itself in broken plastics. The angle of the ball when hit by the multiball trough kickout woud result in the ball hitting the underside of the plastic covering the trough. Over time it would cause the plastic to break off a sizeable chunk of the corner. The solution was a metal plate installed under the plastic, which is totally invisible when installed. It appears to also be very effective in its job. Thisftp://siegecraft@www.siegecraft.us/pinball/bkoutlanedifferences.gif can be a big deal, as this is a large plastic that wraps around the whole top-left corner of the playfield. Unfortunately, I don't know of any available sources for this piece. This piece apparently is also used in the 1981 run of Black Knight Limited Edition machines.
ftp://siegecraft@www.siegecraft.us/pinball/bkoutlanedifferences.gif	Seriously, I highly recommend finding one of these or making your own. My plastic is original to the machine, and unbroken. You can also see that the mylar pop bumper ring covers the entire horse graphic in this photo.  Earlier production playfields used a much smaller mylar ring.  This mylar was factory installed, as opposed to all the other mylar in the game that would have been ftp://siegecraft@www.siegecraft.us/pinball/bkoutlanedifferences.gifinstalled by the operator.
Here's a fun one from some very early prototypes that I've seen. The arrows for the multi-ball lock and lower kickout holes. Production machines used green inserts here, but I have seen a few with red inserts instead. These tend to be very early playfields with the extra notches for the abandoned standup targets.  Strangely enough, most of the ones I have seen were machines in Australia.  Go figure.
Green arrows will be shown here	red arrows will be shown here
On the very left edge of the playfield, next to the left side ramp, there's an annoyingly blank looking section of black wood. It just looks like it's unfinished and missing something, correct? That's because it is! Originally there would have been an additional red plastic piece there, which does show up on some occasions. It even shows up in the original sales flyer, if you look closely. Update: The recent CPR re-run of Black Knight plastics now includes this piece.  It's also (As of May 2011) available as a separate piece from some sources.  I'll be installing it onto my own shortly, and will be updating the photos when I do.
No plastic shown here	plastic shown here
Here's one that I never would have spotted, if it hadn't caused me such a headache. The physical construction of the backbox changed at some point during the production run. Earlier machines, like all the system 6 games I've seen, had the sides of the back box attached with simple butt joints. Somewhere during Black Knight's run, they opted to get fancy and changed the type of attachment joint. Unfortunately, it made the box very weak if you pushed it foreward or backward.
What about those drop targets? I haven't nailed down when this change was made, but there were two different styles. One with the more common rose colored background. But there were also some seen with a blue background instead. Nifty, eh?
rose drop targets	blue drop targets
At some point in the design process for Black Knight, the drop targets were likely intended to work more like older machines. I suspect that the timer feature was a later addition. Very early machines have a perpendicular notch behind the drop targets, that would have featured a standup switch. This switch is only exposed when any of the drop targets is down. I have never seen a machine with these switches or their wiring present, and don't know how early in the design process that the feature was changed. I'd love to know more about this. As a fun note, should you wire up these switches, the software does still support them for scoring purposes. 10pts per hit. They are also listed still in the instructions.
Upper Playfield Notches.
Speaking of software changes, Eventually I would also like to document the changes between the various ROM revisions that Williams released. Revision 4 is the latest available, and is what is commonly seen for download.  If you have any ROM versions other than 3 or 4, I would LOVE to get a copy of them. I'd happily accept whole chips, e-mailed files, or any other way you can think of to get them to me. I have decompiled a lot of the L4 ROMs, and also compared them to the L3 ROMs.  I found no rules changes between the two sets, and only a couple bytes difference in memory allocations.  So the L4 was a very minor tweak over L3,  and most users will probably never notice a difference between the two.  I suspect that L2 is a very different ROM set,  but have so far been totally unable to find it anywhere.  More info about that on my "Black Knight Mystery" page.
Here's an interesting one that recently came to my attention.  On the left side outlanes, apparently there was a spot that kept having issues with flaws in the screen printing.  Here's 4 different playfields, thanks to Jon Owens, that shows the affected area. The first one, you can see that there is a lot of black ink dropped out, both the area fill and the scrollwork for the rollover switch.  The second one, the scrollwork is ok, but the black fill is still missing.   Third photo is mostly there, with just a small white gap. Fourth is a new CPR reproduction, where this has all been corrected.   You'll also notice the yellow border artwork as well.  This gets covered up by the side rails once the playfield is installed.  From what little I can see, this was also missing on the three original playfields.   Unfortunately, I never checked this on the two original playfields I used to have,  prior to swapping a CPR playfield into my own machine.
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To Be Continued!

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