The Playfield – Underside

The rebuilding of the underside of the playfield is just as vital as the topside, as located here are all the mechanical components that provide you the player with the interactive experience with the upper playfield. When I start on the underside the topside has already been stripped, and all components protruding up to the topside have been dropped. All major assemblies such as flippers, slingshots, vertical up kickers, drop targets, stand-up targets are hanging, or removed by this point (Figure 2.1 – 2.4). It’s very important to clean the complete underside playfield, if not all the oils and carbon dust will quickly transfer to your just restored / cleaned topside through vibration, and ball travel. Most 12 year and older undersides will look like this (Figure 2.5) when I receive them, and when done will look like this (Figure 2.6).

As I start rebuilding the underside, I usually start replacing / cleaning all the smaller items first, such as lane rollover wire forms, lamp sockets, and lamps, switches, and standup targets. These are done first as the major assemblies are already removed. Once they are back in place, many smaller components cannot be accessed.

Rollover wire forms are one of the first components reinstalled. All receive a hand polish with a special metal polisher, to bring back their original look (Figure 2.7 – 2.9). All of these activate a blade switch. At this point each has the contacts cleaned, and solder connections checked.

Next all fixed mounted under playfield switches contacts are cleaned, & solder points checked.

Then, all switches that protrude through to the upper playfield are cleaned / fixed, or replaced, and reinstalled. This includes slingshot activation, standup targets, spinner arms and the like. It’s at this stage when you really see all the broken switch blades, solder lugs, and missing diodes (Figure 2.10 – 2.13). All switch blades are cleaned, but those that are highly visible to the player, such as slingshot (Figure 2.14 – 2.17) are polished to look new, or replaced. Many of these switches over time start to look very unsightly. You don’t want them put back into a game that’s just been restored!

Now that the wire forms and switches are done, it’s onto the lamps, and lamp sockets. I always remove all old lamps, then bend back the lamp socket to reveal the lamp insert (Figure 2.18) This lamp insert is what allows the lamp light to shine through to the playfield. Over the years this insert’s ability to allow light through degrades from a build up of kitchen grease, nicotine, and carbon dust clinging to the former (Figure 2.19 – 2.21) At this point each individual lamp insert is thoroughly cleaned from the underside. Each lamp socket is checked for tightness, and solder lug connections. Over time the isolation material used on the lamp sockets shrink, or the load spring gives out. These lamp sockets have to be replaced. Some are so bad you can tell with a visual inspection, others that are borderline have to be diagnosed after the pin is booted back up. On a Sterns Stars pin I had to replace 28 lamp sockets. All new #47 lamps are installed.

As the underside inspection continues it is also cleaned. The wire harness is cleaned as well. The wire harness is also tidied up, as over the years it gets “opened up” as people trace wiring trying to sort issues. As a tech, it’s very annoying to work on a pin when the wiring is always in the way, so this is addressed.

Fuses located underside have their values checked for correctness. I always write the fuse value directly onto the wood with a sharpie, as over time the original value stickers fall off, due to the glue drying out.

Now that all the smaller parts have been addressed I move to the larger solenoid assemblies. One of the first tasks is making sure the solenoid rating in each assembly match what the original manual called for. I have found it’s very common to find incorrect solenoids installed. This goes back to operators using whatever was on hand to keep the pin earning quarters. I have seen my fair share of pinballs with totally smashed plastics, ramps, drop targets, and metal posts bent over because someone put the wrong solenoids in the flipper assemblies.

Each solenoid assembly is stripped apart one by one , rebuilt, and reinstalled.

Most pop bumper upper playfield parts are just replaced with new (Figure 2.22). This includes the main body, metal rod & ring, and skirt activator (Figure 2.23), as most of these parts are broken, and at the very least cracked (Figure 2.24).

Slingshot armatures many time are broken and need replacing (Figure 2.25).

All solenoid assemblies share most of these common parts, a coil, plunger with link, plunger sleeve, spring, and coil stop (Figure 2.26). Some of these parts at the very least require service, and a few just need to be replace.

The plunger link is either made of fiber or plastic (Figure 2.27) and it’s a very important part. Over time slop will develop where it connects to the plunger with a roll pin (Figure 2.28 – 2.29). If you rebuild a solenoid assembly without changing this component, well it’s not rebuilt, as this is the weak “link”. If it shows any signs of slop, I change it.

Return spring should always be changed, just based on it’s current age.

The plunger link and coil stop smash into one another each time the solenoid is activated, this leads over time to a mushrooming effect on both (Figure 2.30). If the damage is not too bad they can both be filed back to original shape, or changed.

The coil “sleeve” in all cases is changed, as the plunger and stop smash into each other inside this sleeve which scores the inner lining.

Examining all these parts indicates the solenoid assembly has been completely disassembled; during this time the main base frame is cleaned. Many times I will find stress and /or fatigue cracks on the assembly mount structure itself, at that time it’s replaced (Figure 2.31 – 2.32).

The flipper assemblies are an extra special case, as they have some unique parts such as the flipper body, flipper bushing, the crank, and the switches (Figure 2.33). More times than I can count I find large wood screws forced into the metal machine screw holes that hold the coil stop in place. Sometimes this hole can be tapped back to proper use, and other times the whole flipper body base needs to be replaced due to the damage done (Figure 2.34 – 2.35).

The flipper bats, if original, are usually cracked at the cross bracing point. If they are cracked they will not absorb ball hits correctly, and feel weak. These cracks can only be seen if the flipper is removed and turned over (Figure 2.36 – 2.38).

Many people ignore the first switch that starts the flipper process, and that’s the cabinet switch on the left and right inside of the main cabinet body. This switch has evolved over the years from a straight contact, to powered optic eye; either way it needs attention. Buy Used Pinball Machines

Well there are many other components on the underside of the playfield such as resister boards, diode boards, relays, motor starters, and much more.

I just provided you with a very condensed version of what must happen under there to provide you with years of trouble free pinball play.

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