thanks Jonny and Ken. just picked up a "dead" 'flying aces' two days ago (sound, lights, and scoring were ok), one solenoid coil, one bridge rectifier, a few diodes and a power transistor later, it's up and running great. needs a rubber kit and a lightbulb but anyway.. my first impression about these "they need independant flippers!"
no doubt we've all seen the neanderthalish rookie "always push both buttons together yeah" like some weightlifter with a thick accent on a benchpress maybe? simplistic as these playfields are without in-lanes and one outlane on the left side, I still want to (and do) slap the flipper buttons independantly, doesnt work on these things as gotten.
I might go about it a little differently with a solenoid mounted forward center with linkage, because it might pull the ball around on-off path as an advantage or disadvantage, theres enough room and might be simpler too.

I'd found a new compact williams-bally unit at a reasonable price should be here in a couple days oughtta suffice. might have to play with high current low ohm resistors or a different coil if the flipper power is much unbalanced.
I'd also kinda goofed getting a left side unit, but mirror reassembling it wont be too difficult.

someone somewhere around here had called these machines dumb or stupid, well YES THEY ARE..
simplistic, unsophisticated, but they sure can slam a ball around with brutal force! it might be for putting in a 3.1 amp breaker, a much larger bridge rectifier, and two main power transistors in parallel in for the playfield? stuff I had just kicking around here in old computer and other power supplies. I'd never played a sentinel machine before so I cant really KNOW whether what I'd done has made this machine more energetic, its just a possible guess about that.
gotta love a machine that has so little to ever go wrong, and is usually pretty easily fixed.

the left ball-out drain can be TOO MEAN, the ball would hit the wood rail, stop cold and drop, every time!
popped in a 2-1/2" bounce spring there at about a 5-6 degree angle (3/8 from wall at upper, 3/4 at lower, about 3/8 above the bottom of the left flipout wire and 1/2" below the top of the left slingshot) lets the ball bounce back outta there maybe 30% of the time, I think it adds to the gameplay's adrenaline to have a -chance- for the ball to bounce out and stay in play (I'd sure include a photo here if I could figure out how to attach one!). it looks like it grew there belongs there with the thin wedge of plywood painted black, notched for 2 radio control servo blocks that are the endposts for the bounce spring. theres still 2" wide at the bottom from the backside of the slingshot, where the ball still drains 2/3 the time anyway. is it a "cheat"?.. after playing about two weeks now, last night a friend got the highest score I've seen here so far ever, was 113,800, lots of skill and luck both! these sentinels will roll over back to zero at 200,000 points, I cant imagine that happening in the 3 ball game but will still ask if its a cheat, while at the same time tell about how much more adrenaline FUN it is with the chance of a bounce-out from the left side ball drain. Jonnyfri, you might like this tidbit, the bouncer mounts with two very small screw holes in the side wood, not the playfield, so if-when it's removed, you wouldnt much notice it was ever there.

flipper mechanism arrived and with a little creative persuasion, aka pounding the thick sheetmetal stop tab 180 degrees to flip the main plate from being a left into a right, it works perfect. wiring it up was a little different than I'd expected, the "yellow" wire bottom of left flipper needed a jumper across to the bottom of the right flipper, then the new right side wires up about same as the existing old left one, with its own seperate holding resistor to the switch.
it had to have its own holding resistor, or left-right switches would defy each other and not include it to the circuit.
gameplay definitely improved a bunch, can now use flippers tips independantly to make drain saves sometimes.

it took a little persuasion to make the old flipper bushing fit the flipper plate too, the 3 mounting holes a slightly smaller pattern than the plate, so the bushing holes got drilled barely larger than what was stock. also had to drill a couple holes for the solenoid stop bracket to hold the shorter length solenoid, and shim that bracket a little taller with a couple small washers to match the height because of making a left bracket into a right one, the threaded inserts for the plunger stop being inside instead of outside. even with the extra work making a lefty a righty, maybe an hour or so to get it together and running. the old left flipper without the mechanically linked right one hits a little better now, and the new right one maybe hits a little harder for now until I pop in a better matched coil. easy project.

-very minor bug.. if the left flipper is held down, the right one wont fire, is really something you just get used to.
once you know to not hold the left down or try to slap the buttons simultaneously it really isnt a problem at all.
for the end of stroke switch I copied what is on the left side with two 10w 40-ohm in parallel for 20-ohms seems to be doing the job keeping the single wound coil from heating up when holding, it really seems the simplest solution.

I sold the Flying Aces, a buddy HAD to have it.. which is OK, I can play it any ol time at his place and I'm picking up a Demolition Derby machine today, I like the paintjob-theme of it more, even though its exactly the same machine. sooo here I go again with the independant flipper mod and I already have the parts to MAKE it happen, converting a slingshot or kicker mechanism into being one for a flipper with a little creative metalworking, easy enough! I'll be putting in the spring bouncer to the left rail ball drain, and covering the "dive bomb alley" wire with small vaccuum hose is better looking, doesnt CLANK when the ball hits it either.

we'd found something else cool helpful to gameplay, 3 coats of wax to the playfield then a coat of armor-all's "tire gel" makes the playfield REALLY slick and slippery (all excess has to be wiped-polished clean of course). same thing did wonders for ball speed in my zizzle PotC (toy!) machine. the stuff hasnt interfered with the ball as part of the electrical contact circuit, but it sure gets around lots faster smoother quieter. sometimes, its just a blur hehe.

the "dumb machine".. my buddy thought so too the first game he played on it, but by 4th game he was hooked.
there is zero strategy unless "keep fast ball in play make points" counts as anything strategic (lmao). simplistic sure doesnt mean they wont get ya with straight up adrenaline, and for that I think Sentinel-WonderWizard's are great!
later today I'll begin to know whether bone stock gameplay is slower and less exciting. the Flying Aces had the main bridge rectifier, a coil, a power transistor and a couple diodes, all dead when I got it. I'd replaced the coil, put in larger rectifier and transistors.. I suspect that may have juiced it up some, but dont know (yet!).

oops.. sorry Ken, a) I had the flipper mechanism in and running near instantly this time.. it was either a ball kicker or slingshot mechanism before I tweeked it into being a right flipper mechanism, was really easy to do.
b) I havent figured out how to post pics here, help!!?
I tell the site insert-upload page where it is on my hdd and it wont grab and post, does it need to be hosted elsewhere?
- I really wanted to show a pic of the steep angled 2-1/2" long left drain bounce spring, would have been simpler for others to just see, how it'll keep a ball in play maybe 30% of the time instead of an always guaranteed stop-n-drop.

I'd also put in LED's from a niftyled-dot-com site, pretty reasonable prices, quick shipping, and I wont have the hassle of opening it up to change failed bulbs on a semi regular basis anymore. they're actually a little brighter but somehow seem a little dimmer, and theres a little bit of strobing (ghosting?) when the ball moves really fast.
the static ON bulbs dont flicker in sympathy with the 4 flashing LED's like the old incandescents used to do, which was kinda cool but.. changing failed bulbs often was more a bummer.

buddy just picked up a demolition derby and star explorer. cleaning the pop-caps the red paint washed right off!
pretty sure they just too old and baked, the paint anyway.. wasnt much more than a touch.. poof! we decided heck with it and washed em completely white, star explorer is going to get 4 fast blinking color changing LED's in em oughtta look pretty cool there anyway. looking for couple right flipper mechs or whatever parts to make em work for cheep real soon.. like the hardware that came attached with some used coils just got from ebay sure was nice-easy.

after looking around, the unit I'd used was a for a slingshot. two of the e-bay used coils I'd picked up had mechanisms or brackets attached, sure was handy. the used 900 coil was definitely too hot (powerful) as a flipper, solved with a 10w 3-ohm resistor in series is now about equal to the hit of the stock coil running the left flipper and hasnt popped the circuit breaker since its been put in. hadnt bothered with a holding resistor, no real need for one when you get used to just tapping the flipper buttons when needed, to avoid the left flipper cancelling out action of the new right flipper, if left is held down the right flipper wont respond is something you just get used to on it.

the Star Explorer with the now white pop-caps look great with the 4 RGB fast blinking LED's in em, not quite as bright as I'd liked to see but at 1.60 each no real complaints either.

the last couple of these I'd done was with used slingshot mechanisms, creative butchery with a hacksaw to fit. it was just a matter of aligning the coil+plunger at height, angle, throw distance, before locking it in place with screws. I know its a "run what ya brung" -hack-, a 10w 3 ohm resistor got the now flipper mech coil at about balanced the strength to the existing stock one. got 2 used (with coils) slingshot mech and a hole kickout for 10 bucks through fleabay, made them work.

yes real flipper mechs with 3 tap coils and EOS switches is the much nicer arrangement, but the mod can also be done "down-n-dirty" to work out allright. heavier bridge rectifier from an old PC power supply, power transistors too in a pinch (ohm meter test for similar behaviors).

spring-savers..

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they bounce the ball back out of the drain roughly 30% of the time, definite adrenaline booster helping the games be a little more fun, not the 100% stop and drop like stock does. these were done with large triangle slivers of wood and RC servo blocks, they can also be done with posts and a band.

again note: with right mech parallel tapped in from left side across, right may not fire if left is being held or buttons hit simultaneously.. you get used to that very quickly, is not really much a problem when you tap left-right or right-left independently, was the point to begin with anyway..

even more recent.. I'd unscrewed the chain hanger for its (cheezy lol) tilt mech and shortened the chain one ball (no cutting needed) to bring the bell more up into the ring. ring got slightly adjusted to center it up, making the stock tilt mech a bit more sensitive. idk, seems fair to me after independent flippers and drain bouncer, try to shake too hard to bounce back out of the left drain = tilt penalty.

sure they're simple machines, I think simple little mods (now 3) helps them be a little more fun.