I also wanted to clean the score reels, but for purposes of this post, I am using a used spare Bally Score Reel that I purchased on ebaY. If you can find them for a reasonable price, consider getting one or more spare score reels for the game(s) you own. They can be a nice supply of the following spare parts that you will have on hand in case anything goes wrong:
Score Reel, Coil, Coil Stop, Coil Sleeve, Springs, Hitch Clips (Bally refers to them as 'Hairpins' in their parts catalog) or C-Clips, switches, armatures, etc.
So here is a nice set of 4 Bally 3" score reels that I bought:
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After removing one of the reels, here is the side view. Note the 3 screws and the hitch clip that connect the score reel to the ratchet underneath:
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After removing the 3 screws and the center hitch clip; Note the 2 tiny hitch clips that secure the hold pawl (left) and the rocker arm (right), as well as the 2 springs that provide return tension for the hold pawl (left) and the drive pawl (bottom):
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You should also note the position of the rocker arm in relation to the switches in the switch stack:
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After removing the 2 small hitch clips and 2 springs, I removed the ratchet, hold pawl, rocker arm and drive pawl. They seemed a bit dirty, and my OCD kept saying, 'Clean me......':
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So, 5 minutes later after a dip in the ultrasonic cleaner and some shots of compressed air, they looked much better. I must say that I can be a 'clean freak', in that it may not be necessary to clean a part in order for it to work perfectly, but if I have the means to clean it, I will. This is the main reason why any pinball project I work on seems to take way longer than most people would expect. But hey, this is therapeutic for me, and if I have the tools, I may as well use them Harbor freight makes a nice ultrasonic cleaner that does a decent job for only $65 after their 20% off coupon (http://www.harborfreight.com/25-liter-ultrasonic-cleaner-95563.html). I will usually use this for non-printed plastics (Posts, Lane Guides, etc.), using Dollar Tree 'Amazing Orange' cleaner (At $1 for a 1/2 gallon, you can't go wrong), and will rinse under warm/hot water when finished and just let air dry. However, since the drive pawl has a metal component, I also made sure to blast that part with compressed air to remove all moisture.
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So now we have a clear view of the printed 'circuit' board, which can be cleaned / lightly sanded / lightly lubed. In addition, I will clean the 3 'posts' that hold the ratchet, hold pawl and rocker arm with isopropyl alcohol, in order to remove any 'gunk' that may have accumulated over the years. It should be noted that these 3 posts do NOT need any lubrication.
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Here are a couple of photos of the coil stop. Note that it is nice and flat and not 'mushroomed'. This happened to be the 10 point score reel in the set, which usually gets the most amount of use from all of the points via the pop bumpers and slingshots, so it would stand to reason that it's coil stop would be most likely to get 'mushroomed'. This is where getting a spare reel or tow or three can come in handy, especially if you can have the seller verify ahead of time that the coil stops are in good shape.
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After reassembly, minus the score reel itself:
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