Do you have to clean or prep any of the parts before you send them to be plated? How much roughly does it run to have it done?

I have them installed on all my Sterns and some Bally/Williams as well. The originals are just about indestructible - I've had more broken metal rings over the years vs. none of the plastic (although the plastic ones can warp).

You do have to sometimes change the way they're mounted, but it's pretty straightforward to do so. The extra speed they activate is the main reason I did it, just changing the metal ringed variety's coil to a strong one will get the down stroke faster, but the spring can only pop the heavier metal ones back up so fast for next time. They really do make the pop action very snappy.

Yep, as seen on Classic Sterns from Cheetah onwards. (Cheetah must have been the game they started on with it, because I had 2 cheetah playfields at one time and one had metal, the other plastic). Lots of people get games like flight 2000 in (me included, about 20 years ago) and it had one plastic and one metal - at the time, I said "what's this plastic crap doing in here" and changed it to metal..... that's before I knew the error of my ways, and I changed it back. Bought a whole bunch of the plastic mechs at expo ten years ago or so, just to get the rings.

The original Black Knight pop plays amazing with the plastic ring in it, it's quieter, for one thing, and you actually get some ping ponging pop action occasionally out of it (instead of it just being an obstacle to the lock shot)

What's a bell?

Here's photos of a complete mech I bought (off a Wico Aftor, same pops as later sterns.) and a couple plastic rod and rings vs. the original metal

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Ummm I think I might have been the first to get one a long time ago.... even Maestro Classic_Stern didn't think too much of it at the time he shipped it to me.

It came from your neck of the woods in fact.... some one in KC emailed me out of the blue and got it for me and Bill shipped it to me..... he didn't think too much of the playfield at time but I see he's corrected himself since then. I know I inspired both Slam Tilt guys to get one (and other classic sterns since they both played the mpu200 collection when I most of them)

I used to have all but Iron Maiden and Ali of the mpu 200 series. Foolishly, I sold 1/2 of them before the crazy price hike happened. I don't really miss them, but I wouldn't have minded getting 8-15x what I'd paid for them, instead of selling them for close to what I paid.

The transformer differences is one of those mystical things that have been repeated over the last 30 years to describe classic stern "mojo". I would like for someone to actually test this difference out. The problem is, you need a large-ish sample size - so you don't get an exceptionally weak or strong transformer of either type to skew results.

Especially in the case of new builds of Quicksilver machines - what on that machine is drawing so much current that would require the beefier transformer? 2 flippers, 2 drop banks, 3 pops, no multiball. The pops will get a work out that's for sure but either -3 or -6 transformers should be loafing most of the time.

I do wish that people building the QS's would mount the transformer and rectifier down in the body like it "should" be. I'd assume that the main enemy of the transformer losing power would be the heat that builds up in the coils, and the head is definitely the center of the heat production in the game.

For that matter, you're building a whole new game - go crazy and juice up the coils to 50 volts with a Williams transformer just for the coils. (Heck, high tap the -3 transformer!)

I wonder if that's a contributing factor to how the transformer differences got started.... maybe someone had a -3 jumpered for 120 v input, and a -6 for 110 v, and WOW what a difference when they swapped (as you'd expect....)

Cure it? I thought the purpose was for all solenoids to be snappier - that's certainly what's happening when you remove windings from a coil.... snappier coils. There's only 3 variables here.... voltage, current, and resistance.

Don't change anything on your coils, resistance is the same, bump the voltage up - the current draw will be less. (i.e. high tapping)
Don't change anything on your coils, resistance is the same, bump the voltage down - the current draw will be more.
Lower the resistance on your coils by unwinding a couple hundred winds, or change the coil, voltage is the same, current draw will be more.

So basically - you want the extra current capability (if that's what the -6 offers) if you have a "hot" coiled machine, that's going to get a lot of play, over a short period of time.

....which is affected by the label on the solenoid driver board that tells you to use a 5 amp for 2 flipper games, a 6 amp for 3 flipper games, and a 7 amp for 4 flipper games. (Or maybe 7 amp for 3-4 flipper games I forget what my seawitch has on it). Sounds like a compromise of fuse resiliency vs. actual expected excessive current draw. The problem with fuses comes when idiots put wires or bolts on there giving the transformer and wiring time to melt down.

If your goal in utilizing the -6 transformer is for the snappier coil response over long playing periods (we've all played games even new ones where the power under load sags), subbing in a higher voltage transformer would certainly help, or if you're some kind of power demon (several years ago people were obsessed, and I mean OBSESSED, with getting all 25-450 flipper coils in their stern games. So much so that there was some sneering going on if you didn't have them - "how can you rip the spinner if your flippers are weak", etc. - you know, snobbishness)

That would only depend upon if the game actually NEEDS a 7 amp F4, per Stern's instructions, 3-4 flipper games. Unless the label on the SDB means the SDB itself, for some reason. That's not been documented anywhere but I suppose the only difference there could be fatter traces on the 3-4 flipper games or a heavier duty relay.... or marketing hype!

In a pinch not having the proper 7 amp fuse I've put 5 or 6 amp fuses in there and they're still working. It really depends on the game. A primary flipper coil with a maladjusted EOS is going to blow the fuse no matter what.... just how hot the coil gets before that happens seems to be the variable. After all, EM's have 10 or 15 amp fuses for the flippers - let's put EM transformers in the games to hot rod them!!

If you have ~120v from the wall and you put a transformer wired for 115v input, you will get a slight boost on the output voltages. If you have ~115v out of the wall, and the transformer is set for 120v, you will get slightly less voltage.

If you have 120v from the wall and the transformer set to 120v, you will get the intended voltage levels on the output windings.

Much cheaper to manufacture. Also, traditionally the way it was done way back from the EM days.
Traditions die hard.