Those black 555 lamp twist socket holders are very commonly used in car instrument clusters. So try your local auto parts store / auto electrician / auto wrecker.

Has anyone experienced this level of wear on the Zipper Flipper cranks? Is this common? Has anyone tried to retrofit a different plunger/link/crank that isn't wearing metal on metal?

ZipperFlipper_Left.jpg
ZipperFlipper_Right.jpg

I'd say it's a design flaw - there's not enough metal at the crank hole. I think the 25-500/34-4500 flipper coils are also too strong for the location of these zipper flippers and I'm tempted to replace them with 26-600/34-4500 coils in the hope they reduce the impact on the drop/standup targets.

Since I'm not in the US and parts aren't available where I am, I'm tempted to try and be a little creative by retrofitting a traditional crank/link/plunger that won't wear so much and is more common/cost effective.

Picture courtesy of Marcos showing the original hole position/size.

Crank_Large.jpg

Sounds like your Solenoid Expander isn't working. Go into Solenoid Test Mode and referencing the solenoid test numbers in the manual, take note of which solenoids activate at the wrong time.

These lamps are driven by the Auxiliary lamp driver board. Issue is likely related there.

Post a request for help thread in the "Tech: Early Solid State" sub-forum. There are more techs paying attention there.

Fireball II also uses this post so you might want to post the same in that club thread:
https://pinside.com/pinball/forum/topic/fireball-ii-club-members-only

My end apron brackets are also bent - playfield hangers are straight:

IMG_0009.jpg
IMG_0011.jpg

The zipper flippers do hold the ball when closed on mine.

Yes, those are feature lamps which are all switched on and off during lamp test mode.
Are the 20 rear playfield panel lamps all flashing? these plus the Gorgon lamps are driven by the auxiliary lamp driver board.

Issue must be with the braid wire (that carries 6 volts DC) to the base of those Gorgon lamp sockets.

Last page of the downloadable PDF manual has the coil types.

Disconnect J1 from the rectifier board - that will remove the playfield from the equation, just in case the short is around the front door coin lockout coil / cabinet knocker coil.

Medusa_Coil_types.png

Just curious but why are you using Medusa as a wiring template for Embryon with Medusa's more complicated hardware?

Future Spa has the rectifier board/transformer in the head while Embryon has it in the base of the cabinet. Got any other Ballys of that era?

I have a project Embryon in storage and was actually going to take pictures of it yesterday for you but it didn't pan out. My next visit to it will be in about 3 weeks but I think you'll likely have it sorted by then.
Anyway I do have a Medusa here and am happy to take head wiring pics if you still want them.

The solenoid driver board J3 connector is wired the same for nearly every Bally of this era. Per the Medusa schematics:

J3 Top
1)
2) - key
3) White
4)
5) Yellow
6) Grey-Blue
7)
8) Red
9)
10) White-Brown
11) Red-Green
12) Orange
13) Brown-Green (connects to pin 25)
14) Grey-Brown
15) White-Green
16) Black-Green
17) Green-White
18) Grey-Green
19) Black-Red
20) Brown
21) White-Blue
22) Black-Blue
23) Red-Yellow
24) White-Orange
25) Brown-Green (connects to pin 13)

Pin 13 has a loop wire that connects to pin 25

Below picture example from Embryon

IMG_0021a.jpg

At the top of every thread here is an image gallery of pictures attached within the respective thread. You will find some pictures of the zipper flipper mechs:

https://pinside.com/pinball/forum/topic/medusa-owners-club?gallery#g

Hope these help.

IMG_0004a.jpg
IMG_0010a.jpg

Just FYI, Marcos sells a 3D printed part - might have even been a pinsider who modeled it and probably somewhere in this thread or the Fireball II thread:
https://www.marcospecialties.com/pinball-parts/C-972-1

Six years ago I posted some pics of the zipper flipper crank/pawl wear on my game:

https://pinside.com/pinball/forum/topic/medusa-owners-club/page/10#post-3913477

ZipperFlipper_Left.jpg
ZipperFlipper_Right.jpg

Last year probably only 200-300 plays after those pictures were taken, a friend was playing and we heard a bang in the cabinet to find one of the plungers on the bottom of the cabinet and it's flipper crank hole blown out:

IMG_0013a.jpg

There was no way I was going to install new parts that were just going to do the same thing with metal on metal wear so I made up a more traditional setup - before and after pics:

IMG_0030a.jpg
IMG_0007a.jpg

Excuse the rusty cranks, I'm waiting on new ones to come in.
I made new links from some POM plastic, new metal idle end stoppers and new EOS switch brackets to move the switches closer to crank and higher from the base plate. The new plunger/links probably turned out to be similar spec to Stern gen 2 flippers. The crank/pawls are early solid state Bally.

Yes I fabricated those metal brackets.

I bought a 300x300x3mm black sheet from AliExpress years ago:
https://www.aliexpress.com/item/32852877596.html
There's probably other sellers that are cheaper now.

I believe the grey plastic links used in DMD games is made of POM. Home roller door wheels are made of this material because of its high strength and low wear properties. I use it whenever making new flipper links now. Traditional Bakelite-fibre material could certainly be used otherwise.

The coil plunger/shaft has to be shorter since the original design didn't have a link. My parts seller was selling packs of ten so I don't know what brand/game the plungers are from.

I did spend time measuring to try and make sure the flipper travel was about the same as original and the link angle on the crank was about the same at both extremes.

Nope, I crafted the metal parts the old fashioned way with a vice, hacksaw and hand-drill..

Has your game also suffered from severe wear on the cranks?

If I remember right the plunger and POM link are about the same size as those used on early Stern gen2 flipper assemblies. They can be used as a starting point. I looked at using Williams / Stern cranks but their arm length is short so stayed with using the previous gen Bally cranks.
The steel used was the same thickness as the original.
If you look at the third picture in my post above you'll notice the corner of the base plates are bent up a little so this needs to be taken into account when making the end stops so they sit flat.

If you're CNC'ing then you have the advantage of redoing parts if they don't turn out right.