Sky Jump
Gottlieb, 1974Quoted from spinal:What do you recommend for cleaning off greasy metal parts?
I use 100% isopropyl alcohol and a cotton bud, followed by a clean cotton bud to pick up the remaining residue.
While I'm not sure if it'd cause damage, I would not get it anywhere near the inks on anything.
Quoted from ajfclark:Those grommets are unobtainium as far as I'm aware. I haven't been able to track down a substitute where I live either.
:PBR has them
This is a spring hook set which hoov alerted me to sometime ago (US supplier). I have found all of the components really useful & helpful.
I put up a youtube video a few years about this. If you reassemble in the in the right order, you really need no special tools. In fact, you can probably get away with just using your fingers. Small screwdriver at most.
Quoted from boilerman::PBR has them
Awesome. Last time I asked Steve said they were custom made and didn't have them. That was obviously a while ago as I just found this little note in the PBR news section from 2015 though:
The story of GTB-986.
Once upon a time, when Gottlieb® first introduced drop targets, they used a funny "abbreviated" plug bumper for the trigger arms to reset against. The design was okay but over time the rubber got a groove worn into it, then fell out or was lost and the arm then reset too high. This caused the bottom of the drop targets to be over-stressed and then the lip broke off and the targets reset against the bottom of the playfield glass and would not drop correctly. We never found the source of the bumpers, cost to make a mold too high, etc., etc.
Fast forward to 2015 and one of our customers, Larry Dale in Washington state (obviously a person with too much time on his hands!) got curious, did some research and came upon several candidates. He was good enough to forward that information to me. I researched the leads and ordered samples, and bingo! we found the correct original bumper.
I have ordered stock, it has arrived. It is stocked here as GTB-986 and is priced at 0.30 each.
(happy) end of story.
Steve
I've corrected my previous post.
For cleaning switch contacts I'm using here a Dremel with #443 wire brush as seen in Nic's great tour thread:
https://pinside.com/pinball/forum/topic/nics-american-pinball-tour-aka-im-coming-to-fix-your-games
He is a proponent of:
1. Wipe switches with alchohol swab
2. Polish switches shiny with Dremel
3. Wipe again with alchohol swab
I've seen 91% isopropyl alchohol recommended but I'm using 99% (that's what I found online). I spray a bit into cap and then dip cotton swabs into it.
Bend the switch blade back a bit, then, for each switch contact, alchohol swab, polish and swab again - see how all oxidation and carbon is removed from the contact. Works great. Remember goggles since it's possible that loose wires could fly off - I use the slowest setting on my Dremel.
The smoother the movement of plungers within solenoid sleeves the better. To that end, time to polish smooth the reset arm plungers.
Anyone could argue that this is going too far and maybe they'd be right, but I have the target assembly apart and it only takes a few minutes to do this so I argue why not do it 100%? 
Here is the reset arm before polishing along with the 600 grit sand paper sheet from which I cut out a small piece.
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After sanding rotationally as well as along length of plunger, I then polish with Mother's Mag and Aluminum Polish which is recommended by many here on Pinside including "grand-tour Nic".
Zoom into the pics to see what a big difference this makes going from pocked and uneven to mirror-smooth.
Second pic is before, third pic is after sanding and last pic after polishing. There is a large difference in feel after polishing - very smooth.
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==========================
Parts I needed arrived so time to rebuild...
I ground off the peened-on factory coil stop using my Dremel on high speed - quick and easy. Wear safety glasses and put bracket in a vice so you have both hands free to hold the Dremel.
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Parts to assemble:
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Important: Press firmly on both sides of coil to remove slop before tightening.
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After assembly:
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I may still have to adjust later but for now I tried to match original screw locations on the adjustment brackets below. Below are MikeO's important comments on these (thanks Mike) so I wouldn't have taken these off to begin with:
Quoted from MikeO:Don't take the coil mounting bracket off of the main frame. It is factory set for the plunger to correctly bottom out to the coil stop. Once you take it off you will have to make an adjustment that is not totally obvious to get it back correctly.
Quoted from MikeO:Your goal is to have the plunger bottom out just as the drop targets rise above the frame and catch on top of the frame. Adjust the coil too tall and the targets won't push up high enough to catch. Adjust the coil too low and you run the risk of breaking the stop tab off the bottom of the targets.
You should have some evidence of where the screws were positioned relative to the slotted holes to get them close to where they were to begin with.
Good luck.
Next, I attached coil brackets to pivot plate using 4 screws:
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Shot of parts to assemble at this point. In bag are new reset arm springs (A-13455) to replace old ones. These new springs have more tension so I'm happy I purchased new ones as they have a lot of work to do pushing the large reset arm.
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Next I inserted the reset arm plungers into sleeves. I had previously considered disassembling the plungers from arm (just for learning exercise) but decided against it:
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Next step is to insert drop targets into the guide plate and attach springs. The new springs from PBR are in the bag (A-12178 in GTB parts manual but PBR has replacement part number A-18995).
However, these new springs (A-18995 on right) have larger radius and the tension on them is quite a bit less than original factory ones so I decided to stay with my original ones for this rebuild. But ultimately these springs serve the purpose of keeping each drop target pulled forward onto each drop's ledge when targets are up so having exact tension here might not be as important.
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Insert springs the following way using spring tool or screwdriver to push end over each hook.
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Quoted from ajfclark:Looking spiffy!
Thanks!
Next is to feed the triggers through the target slots like so:
The 517 springs pull each drop target downward. I decided to get new ones from PBR and found that they were exact same size and felt like they had a bit more tension. My originals would probably have been fine but went for new ones anyway since they are cheap.
Im putting these onto the other guide plate that has the reset arm adjust screws on it (which I didn't remove so still set at factory).
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I found it easy to put the springs in each hole using pliers:
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As MikeO mentioned above, it's important that the targets just barely reset when plungers hit their coil stops. Tested that here and it was perfect so no adjustments were needed to coil brackets yay!
So here it is, a 1974 Gottlieb Sky Jump target assembly in all its shiny glory
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Quoted from ajfclark:What's the go with your red pop?
In the middle of rebuilding pops.
Very good work, that bank of drop targets looks so much better now especially without the horse! That's a very nice looking playfield too!
FYI, next time you need chemicals, you can actually get a lot of your supplies locally. 99.9% Isopropyl Alcohol, solder etc...you can get from MRO Electronics (10512 178 St NW Edmonton AB). You can get VM&P Naptha from Sherwin Williams. And if you ever take on airbrushing or even 2PAC clearcoating (with SprayMax 2K) Maple Airbrush Supplies (also here in Edmonton) is a very good start.
Keep up the good work, looks great!
Quoted from klr650:Very good work, that bank of drop targets looks so much better now especially without the horse! That's a very nice looking playfield too!
FYI, next time you need chemicals, you can actually get a lot of your supplies locally. 99.9% Isopropyl Alcohol, solder etc...you can get from MRO Electronics (10512 178 St NW Edmonton AB). You can get VM&P Naptha from Sherwin Williams. And if you ever take on airbrushing or even 2PAC clearcoating (with SprayMax 2K) Maple Airbrush Supplies (also here in Edmonton) is a very good start.
Keep up the good work, looks great!
Thanks for your comments and info - much appreciated!
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Oxford, PA
