How do you restore a Bally Lost World pinball machine without turning it into a giant side project that never quite works? Start with power, not polish. That is the big lesson with this game. Lost World sits right in that early Bally solid-state period where one bad connector, one tired regulator, or one crusty battery area can make the whole machine act possessed.
And this one is worth saving. Lost World is a cool piece of Bally history, with early fantasy art, a photo backglass, and the first Bally electronic sound setup instead of traditional chimes. If you want to restore a Bally Lost World pinball machine, treat it like an electrical restoration first and a cosmetic restoration second. I know that is less fun. It is also the cheaper way to do it.
Start With Documentation and a Safe First Power-Up
Before you touch a board, get the manual, take photos of every connector, and make a simple parts and damage list. On Lost World, the manual identifies the main backbox hardware as the rectifier board, the solenoid driver and voltage regulator board, the MPU, the lamp driver, and the sound module. That matters because early Bally repairs get messy fast if plugs are swapped, connectors are half-seated, or somebody before you made “repairs” with electrical tape and hope.
I would also do a slow visual pass before powering anything. Look at the backbox first. Check for battery leakage on the MPU. Check for burnt header pins, cracked solder joints, hacked fuse holders, and brittle connector housings. Then look under the playfield for broken switch blades, missing coil stops, cracked sleeves, and loose hardware. A lot of these games look rough because they are dirty. A lot of them also look fine while hiding electrical damage. The second problem is the one that costs you real time.
Then verify the fuses against the manual, not against whatever is already installed. Lost World’s rectifier board uses six fuses, and the manual also calls out a small fuse on the solenoid driver and voltage regulator board. Never assume the fuse in the game is correct just because it is there. Old Bally machines have a long history of someone tossing in a larger fuse to “get it going,” which is a great way to cook a board.
Rebuild the Power Chain Before Anything Else
The fastest way to restore a Bally Lost World pinball machine without wasting money is to rebuild the power chain first. On this game, that starts with the AS-2518-18 rectifier board and the AS-2518-22 solenoid driver and voltage regulator board.
The rectifier board is where a lot of Bally pain begins. Burnt connector pins, loose fuse clips, tired bridge rectifiers, and heat-damaged solder joints are all common trouble spots on games from this era. If the board is original, I would expect to do real work here. At minimum, inspect and usually replace the header pins and re-pin the female connectors if they show heat damage. Just reflowing ugly solder joints can help, but on early Bally power boards, worn pins themselves are often part of the problem. If you remove and remount the rectifier board, use proper heat sink compound where the bridges mount. This is not the place to get lazy.
Once that board is solid, move to the solenoid driver and voltage regulator board. That board is doing a lot. It handles coil driving, regulates the logic supply, and also generates the high voltage used by the display system. The manual shows a +5V regulator in this area, and the Bally board design also routes display high voltage through it. So when this board goes bad, you can get resets, weak coils, blank displays, or some ugly mix of all three.
Measure before guessing. If the MPU will not fully boot, the +43V solenoid side deserves attention because Bally’s own theory manual ties the seventh MPU flash to the zero crossing detector and the +43V solenoid line. In plain English, if the machine never gets that far, the problem may not be the CPU at all. It can be power.
Repair or Replace the MPU Board the Right Way
Lost World uses the AS-2518-35 MPU system. And yes, the battery area is the first place I would inspect. These boards used on-board batteries, and that is one of the classic failure points on Bally games from this period. When they leak, they do not just make a small ugly spot. They eat traces, connectors, sockets, and nearby components. Worse, they can travel farther than you expect.
If the battery area is clean, great. Still inspect it closely. If there is any corrosion, do not just scrape the obvious green stuff and call it fixed. You need to neutralize, clean, inspect traces, inspect through-holes, inspect sockets, and inspect the nearby connector area. A Bally MPU can have enough damage to boot on the bench and still fail in the game because the connector area is compromised.
The good news is that Bally gave you a very useful quick check. Watch the MPU LED. A healthy board goes through its boot routine and reaches seven flashes. That sequence is basically your map. It steps through ROM, RAM, the two PIA chips, the display interrupt circuit, and then the zero crossing detector tied to the solenoid side. If the board stops early, you have a direction. If it never flashes correctly, do not move on to cosmetic work yet. You are not done with the important part.
This is also the moment to decide how original you want to stay. If the board is lightly damaged, repair it. If it is deeply corroded, a quality replacement or NVRAM-style memory solution can save a lot of frustration. I would not call that cheating. I would call that wanting the game to work next year too.
Stabilize Displays and the Sound Board
Old Bally displays can send you chasing the wrong problem. A blank or flickering display is not always a dead display glass. It can be a connector problem, a high-voltage problem, a header-pin problem, or a display board issue like a failed decoder.
Start at the source. Bally repair notes point you to the solenoid driver board for high-voltage checks. If the high-voltage section is working, you should see roughly 170 to 190 volts DC at the relevant test point, and the line leaves through the J3 connector on the solenoid board. From there it is daisy-chained across the displays. So if you have flicker or blanking, inspect the solder joints on those headers, inspect the connectors, and inspect the display board headers too. Cracked header joints are a classic cause of fast flicker on these systems.
Lost World also deserves a little extra attention on the sound side because it was Bally’s first move into electronic sounds. The manual identifies the sound assembly for this game, and Bally’s theory documentation explains how the sound module takes address information from the MPU to produce tones and effects. In practice, that means you should inspect the sound board like any other stressed single-sided board from this era. Look hard at header pins, supply connections, pots, and old solder joints before you start assuming rare chips are dead. A flaky connector is still more common than a magical mystery failure.
Rebuild Flippers, Coils, and Switches
Weak flippers on a Lost World are usually not one bad part. They are wear stacked on wear. Old sleeves, sloppy plungers and links, pitted EOS contacts, worn coil stops, cracked bushings, and tired cabinet button switches all add up.
So rebuild the assemblies as assemblies. Do not just throw coils at them and hope. Bally repair notes are pretty blunt here. At minimum, the flippers should be disassembled, inspected, fitted with new sleeves, and reassembled correctly. Better yet, replace the high-wear parts while you are in there. Make sure the flipper bushings are not cracked and that the bat sits at the right height with a little vertical play so it does not drag and chew the playfield.
Switch work matters just as much. Bally’s theory documentation explains that the switch matrix reads valid closures over multiple zero crossings, and it ignores certain stuck states. That is good design for the time, but it also means dirty or badly adjusted leaf switches can create weird intermittent behavior that looks like a logic problem when it is really a switch problem. Go one switch bank at a time. Clean gold-flashed contacts gently. Do not sand everything just because it looks old. Bally repair notes also point out that EOS and flipper cabinet contacts are different from the gold switch contacts used elsewhere, so use the right cleaning method for the right switch.
And here is one easy diagnostic that saves time: if the flippers work but most other playfield coils do not, check the under-playfield fuse before blaming the driver board. Bally games from this era can hide a simple fuse problem inside a much larger panic.
Clean the Playfield Without Sanding Off Its History
This is the part people rush, and it is where they get into trouble.
A Bally Lost World can have a gorgeous comeback if the playfield is dirty but fundamentally sound. It can also get worse fast if you clean it like a kitchen counter. The safest first move is boring. Vacuum everything. Remove loose dirt. Pull plastics as needed. Clean parts off the game where possible.
For a true restoration cleaning, conservative hobby guidance favors naphtha on the playfield because it removes old wax and grime without raising the wood grain the way water-based cleaners can. That point matters a lot on old playfields. If you use Novus 2, use it sparingly and only where it is really needed. It is abrasive. It can help with scratches and ball swirl, but it is not a miracle bottle, and it is not something I would casually scrub all over an original playfield.
After cleaning, protect the surface. Use a non-silicone carnauba-style wax. Replace the balls if they are scratched, pitted, or dull because bad pinballs act like sandpaper. Replace the rubbers too. The Lost World manual includes the rubber sizes and playfield map, so there is no reason to guess.
Lost World also has one of those nice little game-specific details that tells you whether a restoration is thoughtful or half-done: the Dragon’s Den area. The manual includes trapped-ball instructions for loading one of the 1/16-inch balls through the slot in the top plastic and specifically warns not to force a ball between the wireforms. So when you are restoring plastics and top-side parts, make sure that assembly is complete, not cracked, and not improvised with the wrong parts. The game feels wrong when that area is wrong.
If you have wear spots, touch them carefully. Acrylic touch-up is the usual route, but be honest with yourself. A bad touch-up job can look worse than honest wear. If the wear is in a high-traffic area, protect it after touch-up with a clear coat solution or a small Mylar patch.
Finish the Cabinet, Backglass, and Final Setup
Once the electronics are stable and the playfield is mechanically sound, then the rest becomes fun again.
Clean the cabinet gently. Tighten the leg hardware, inspect leg bolt plates, and make sure the game sits level and stable. A machine that rocks or sits low in one corner can play badly even when everything else is fixed. Check the coin door switches, tilt hardware, and grounding while you are there because door and tilt issues can cause some really annoying false problems.
Be careful with the backglass. Lost World’s backbox presentation is part of the game’s identity. Clean only what should be cleaned, and do not get aggressive with artwork that has survived this long. A shiny coin door is replaceable. Original art is not.
Then test the game hot, not just cold. Run it long enough for connectors, coils, and regulators to warm up. Play several games. Use the self-test button inside the front door. Watch for resets, dimming, drifting voltages, weak flippers after heat soak, or displays that start clean and then go bad. Early Bally games often tell the truth only after twenty or thirty minutes.
Conclusion
The cleanest restorations are usually the least glamorous at the start. To restore a Bally Lost World pinball machine the right way, begin with fuses, connectors, voltages, board health, and switch adjustment. Then rebuild the flippers and coils. Then clean and protect the playfield. Then finish the cabinet and cosmetics.
That order is not exciting, but it works. Lost World is one of those games that can look decent while being electrically furious underneath. Once the Bally power chain is stable and the mechanicals are rebuilt, though, it turns back into what it should be: a fun, weird, late-70s Bally that actually deserves the floor space.