Pinball Drop Targets Not Resetting: How to Find the Fault on Gottlieb, Bally and Williams

A drop target bank that stays down is one of the most reported faults on solid-state machines from 1977 to 1989, and one of the most commonly misdiagnosed. Owners reach for the driver board when the game is telling them something much cheaper.

The short version: watch when the bank fails. If it resets at the start of a game but never mid-game after you knock the targets down, the coil and driver circuit are fine — the machine does not know all the targets are down, because a target switch is dirty or misadjusted. If it never resets at all, look at the reset coil, its fuse, or the transistor that fires it. That one observation halves the fault before you pick up a screwdriver.

One exception: if the reset coil fires and stays energised, switch off now and read pinball coil stuck on first. A reset coil is one of the biggest in the game and is rated for a fraction of a second.

Contents

What the symptom tells you

Play a game and watch the bank before you lift the playfield. A bank scores when a target drops, holds the target down, and lifts the whole row on command — and which of the three has stopped narrows the fault enormously.

What you see Where to look first
Resets at game start, never mid-game Target switches — the game cannot see the bank as complete
Never resets, not even at game start Reset coil, its fuse, wiring, or the driver transistor
Coil fires but a target will not stay up Lift travel, latch, spring, or a bent target
Coil fires weakly, targets rise half-way Coil sleeve, plunger drag, low solenoid voltage
A target drops but scores nothing That target's switch, or the matrix reading it
Coil energises the instant you power up Shorted driver transistor — power off first

How a drop target bank works

Mechanically it is simpler than it looks. Each target sits on a sprung carrier held up by a small latch. The ball knocks the target back, the latch releases, the target drops and stays down. Underneath, a lift bar runs the width of the bank, and one large reset coil pulls that bar up, re-latching every target in a single stroke.

Behind each target is a switch that closes when the target goes down. Those switches do two jobs: they score the hit, and they report the state of the bank. On a solid-state game the CPU decides when to fire the reset coil, and it decides from what those switches say. That is why a bank can reset perfectly at the start of a ball — where the game resets it unconditionally — and never reset again during play.

One Bally quirk before you order parts: alongside the big reset coil sits a small memory coil per target, and their sleeves are different diameters. Order three of the wrong one and nothing fits.

Step 1: work the bank by hand

Power off, glass off, and lift the bank's plunger by hand — the plunger only, not the coil. Let the targets fall and repeat, slowly, then briskly.

  • Do all the targets latch, every time? If they do by hand but not when the coil fires, the mechanism is sound and the coil is not lifting far enough. Common, and free to fix.
  • Does one refuse to latch even by hand? Then it is that target's latch, its spring, or the target itself — a bent or chewed blade will not catch.
  • Is the bank gritty? Strip it, wash the metalwork, dry it fully, and use a dry lubricant rather than oil. Our maintenance guide covers what to use where.

Two real fixes show how small the margin is. On a Gottlieb Volcano whose yellow targets occasionally failed to latch, the answer was moving the reset solenoid 0.030" to 0.040" on its four mounting bolts, so the plunger travelled far enough to catch every target at once. On a Williams System 7, a bottom target that would not stay up had a washer on the wrong side of the coil's lift foot: "if I push it up by hand the target stays every time", the owner wrote — then, after spotting it, "Swapped those around and had a working drop target in under 2 min."

Step 2: the target switches

This is the step most people skip, and the one that explains the classic mid-game failure. Start a game, knock the bank down one target at a time, and check that every target scores as it drops. If one does not, the CPU never sees the bank as complete, so it never issues a reset.

That is what happened to one owner whose bank reset at game start and ball start but never during play: two of three target switches were not registering. Make sure all the targets score as they drop, clean the switch gaps (a folded banknote drawn through the contacts handles light tarnish), and adjust the switch height so the dropping target actually makes contact. Grey oxide stops a switch conducting long before it looks dirty.

If switches elsewhere also misbehave, treat it as a matrix problem and read pinball switch matrix not working. Bally and Stern games of this era read a 5 × 8 matrix — 40 switches maximum — and the coin-door switch test reports each closure by number, settling the argument in a minute.

Step 3: the reset coil

If the bank never resets at all, start here. Measure the coil's resistance against the manual: an open winding is a dead bank, and a cooked, partially shorted winding reads low and will keep destroying driver transistors until it is replaced. Our guide to testing a pinball coil with a multimeter has the method.

Then pull the coil and look inside the sleeve. Reset coils work hard, and a scored sleeve drags on the plunger and robs the stroke of exactly the travel the latches need. Sleeves are consumable and cost almost nothing. Check the diode across the coil too — fitted backwards, it takes the driver transistor with it. If the fuse blows again the moment you replace it, read a machine that keeps blowing fuses.

Step 4: what fires the coil

Here the platforms genuinely differ. For the wider map of which board does what, see pinball machine electronics explained.

Gottlieb System 1 (1977-1980)

System 1 was tight on outputs: the driver board controlled only eight devices, and as Clay Harrell's repair guide puts it, that "left only three CPU controlled solenoids for the rest of the game (again, perhaps a drop target reset coil and an eject hole coil)!" Solenoid 8 gets a large 2N3055 at Q45, pre-driven by an MPS-U45 at Q29 — the heavyweight output Gottlieb used for a big reset coil. If your System 1 bank is dead, check those two first, and our System 1 diagnostic guide walks the rest of the board set.

Gottlieb System 80, 80A and 80B

The A3 driver board takes signals directly from the CPU and drives up to nine solenoids, using MPS-U45, 2N3055 and 2N6043 transistors. Self-test 17 cycles every solenoid and shows the coil number, so you can fire the reset coil without playing a game — the quickest way to separate a coil fault from a switch fault.

Where a playfield needed more than nine coils, Gottlieb added remote transistors under the playfield, and from Victory onwards a separate transistor driver board — so on a busy 80B your bank's transistor may not be on the A3 board at all. If several solenoids are dead together, suspect grounding first: our System 80 ground mods guide is the fix.

Godri80 replacement driver board for Gottlieb System 80, 80A and 80B, the board position whose transistors fire solenoids including the drop target reset coil
On a Gottlieb System 80 the drop target reset coil is fired by a transistor on the A3 driver board in this position. Shown here is the Godri80, the modern replacement for it. Photo: Pinballs Store.

Bally and Stern, 1977 to 1985

The target switches sit in the switch matrix, the MPU reads them, and the MPU turns on a transistor on the solenoid driver board — AS-2518-16, -22 or -23, identical as far as the solenoid circuits go. Up to 15 momentary and 4 continuous solenoids are available; a reset coil is a momentary one, typically driven by a TIP-102. Which transistor belongs to your bank varies by title, so check the schematic or PinWiki's transistor mapping tables rather than guessing. Games like Eight Ball Deluxe and Centaur lean hard on their banks, so the fault shows up fast.

Williams System 3 to 7

Williams reset coils are computer-controlled, a chain of four parts: a 6821 PIA takes the CPU data, a 7408 logic gate passes it only when both the blanking signal and the computer signal are high, a 2N4401 pre-driver turns on, and a TIP122 or TIP102 grounds the coil.

That chain gives you a clean test. Confirm the solenoid supply is present on both sides of the coil, then briefly touch the tab of the TIP122 or TIP102 to ground. If the coil fires, the coil and wiring are good and the fault is upstream — often the blanking circuit. If nothing happens, it is the coil, the wiring or the supply. On a game like Black Knight, that one test saves a lot of probing.

The LED trap on some Bally games

This one catches people who have just finished an LED conversion. Some Bally playfields use a relay or expander to route the solenoid bus, and that relay is energised from a lamp output, with an ordinary incandescent bulb under the playfield as the load. One Eight Ball Deluxe owner chasing a bank that reset in self-test but never in play found it after a long hunt: "It was the expander bulb!!! There was an led instead of a 555." As a technician explained in the same thread, "The dummy lamp under the playfield helps activate the expander. After the ball drains, that bulb should light, the relay should click, and then the reset coil should pull."

The reason is current, not polarity: on the later Bally expander board, where the same trick is documented in detail, "An LED bulb simply does not draw enough of a load" for the control device to latch. Board and lamp position vary by title, so check your schematic — but if your targets stopped resetting shortly after an LED conversion, refit the original bulb in that socket before suspecting anything else.

When a board is the answer

Most banks that will not reset are a switch adjustment, a coil sleeve, a latch, or 0.030" of coil travel. We would rather tell you that than sell you something. A board earns its place when it has been damaged rather than merely aged: a transistor that fails again after you fit a fresh one, scorched traces, lifted pads. Our comparison of repairing versus replacing a board sets out when each makes sense.

  • Gottlieb System 80 / 80A / 80B: the Godri80 replaces the A3 driver board carrying the solenoid transistors; the GottFA80_Plus covers MPU, driver and power supply together.
  • Bally and Stern 1977-1985: BallyDri for the power and solenoid driver position, BallyFA for the MPU.
  • Williams System 3 to 7: WillFA7 replaces the MPU and driver board together.
  • Gottlieb System 1: ask us about current availability — System 1 boards come and go, and we would rather point you at the right part than sell you the wrong one.
  • To diagnose first: on a System 80 a Lisy80 shows switch states live and fires individual solenoids, settling a target-switch argument quickly. It is built on the LISY project, an independent developer's free, non-commercial DIY project — we supply and support it, we did not create it.

We test boards before they ship and support them afterwards. If you are not sure you need one, ask us first: on this fault the honest answer is usually a switch adjustment.

FAQ

Why are my pinball drop targets not resetting?

Most often a target switch. The CPU fires the reset coil based on what the target switches report, so one dirty or misadjusted switch means the game never sees the bank as complete. If the bank also fails at game start, look at the coil, its fuse and the driver transistor instead.

They reset at the start of a game but not during play. Why?

Because the coil, fuse and driver circuit all work — the game just used them. At game start the machine resets the bank unconditionally; mid-game it resets only when the targets report themselves down. So clean and adjust the target switches.

The coil fires but one target will not stay up.

Mechanical, almost always. Lift the plunger by hand: if the target latches reliably that way, the coil is not travelling far enough, and moving the coil bracket a hundredth of an inch on its bolts often fixes it. If it will not latch by hand either, check that target's latch, spring and blade.

Can I just replace the drop target reset coil?

You can, but measure it first against the manual and any identical coil in the game. Fit a new sleeve at the same time, and check the diode across the coil — backwards, it will destroy the new driver transistor as happily as it destroyed the old one.

Could my LED conversion have stopped the drop targets resetting?

On some Bally games, yes. A relay or expander routing solenoid power can be energised from a lamp output with an incandescent bulb as the load, and an LED does not draw enough current to operate it. Refit the original bulb in that socket as a first test.

How do I test the reset coil without playing a game?

Use the self-test. On a Gottlieb System 80, test 17 cycles every solenoid and shows the coil number. Bally and Stern games cycle solenoids in their own coin-door test. On a Williams System 3-7 you can also briefly ground the tab of the TIP122 or TIP102 driving the coil.

Sources

Stuck on a bank that will not come back up? Tell us the machine, whether it resets at game start, and whether every target scores as it drops — those three answers usually identify the fault. Our technical support is free, before and after any purchase.

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