The Proper Tools
The proper tool to use is a dedicated switch adjustment tool. You can make your own from a section of 3/16″ metal rod – about 7″ long. Then cut a notch with a cutoff wheel from a Dremel. Or purchase one from The Pinball Resource, Marco, Pinball Life, or other pinball parts supplier.
Never use needle nosed pliers. Just do not do it. The angle of the tool seems to result in twisting of switches.
While purchasing this switch adjustment tool, also get a flexstone file.
Other tools required are screwdrivers, isopropyl alcohol (not rubbing), Q-tips, thin cardboard (business cards work). Solder and a soldering iron may be needed if removing or replacing a switch.
Cleaning the Contacts
Prior to adjusting, it is important to clean the contacts. For SS and EM pins with gold contacts, it is easy to clean with a Q-tip and isopropyl alcohol. Isopropyl alcohol is the only exception to the ‘No Liquids’ rule because it quickly evaporates and does not leave a residue.
Caution: Be certain to not use very much isopropyl alcohol and use only in a well ventilated area. Follow precautions on the container.
Sometimes there is dirt that does not come off with the alcohol. In that case, put a thin piece of cardboard between the contacts, push them together and pull the card between the contacts.
With EM games, the power to fire a relay travels through the playfield switches. These switches have silver contacts. To clean these switches, use a Dremel 443 brush or a flexstone file. Flexstone files can be ordered from pinball supply houses. 400 grit sandpaper or a small metal file can be used, but the Dremel brush or flexstone is better. We prefer the Dremel 443 brush as it is less destructive.
In addition to the switches located under the playfield and the flipper switches, EM games have switches in the backbox and, usually in the cabinet under the playfield. Dirt or wear on these switches can lead to malfunctioning games.
For EM silver contacts, they can be cleaned with isopropyl alcohol. Then insert a flexstone between the contacts, press them together and move the flexstone back and forth. It is important not to press too hard and bend the leafs as that will cause them to file not parallel to each other.
The cabinet flipper switches and those at the flipper switches (EOS or end of stroke) handle higher currents, have tungsten contacts and are designed differently*. Worn or dirty flipper and EOS switches will lead to weak or non-functioning flippers. They can be filed with a standard metal file, or they may need to be replaced. A flexstone file used on EOS switches will wear out the flexstone and destroy the file.
Switch Components and Proper Positioning
The most common switch in games is the leaf switch. It is used in pop bumpers, roll over lanes, stationary targets, star rollover buttons, sling shots, etc. The key to making them work properly are to clean the contacts and to adjust them the proper distance apart.
To understand how a leaf switch works, it is necessary to understand the components and what they do. There are two (or more) flexible leaf‘s (also called switch blades). Each of these has a contact. There is usually one or more stationary blades (or dampening blade) that are not flexible.
The longest flexible leaf is the one that moves when the pinball hits. It needs to be positioned against what is moved by the pinball (rubber ring, target, button, pop bumper ring, etc.).
The other shorter flexible leaf is stationary until the moving long leaf hits this short leaf.
The thick stationary blade (dampening blade) holds the short flexible leaf in a fixed position and keeps the short flexible leaf from swinging around or dampens the movement.
The next picture shows a mangled, improperly adjusted, leaf switch. This sort of twisted switch usually occurs when someone uses the wrong tool and adjusts the switch at the wrong point.
Plus, the shorter leaf should always be adjusted hard against the thick stationary (dampening) blade. Here, the shorter leaf is ‘swinging in the wind’. The purpose of the stationary blade is to hold the second shorter flexible blade in a fixed position. That allows the longer leaf to be positioned as close as possible to the shorter leaf, without the short leaf bouncing around causing false hits.
The next picture in this section shows the shorter flexible leaf properly bent against the thick stationary (dampening) blade. Done this way, the shorter leaf will stay in one position, while the longer leaf is moved by the action of the pinball.
This switch is used under a star rollover button. The longer switch acts as the only spring, pushing up the rollover star. The shorter flexible leaf is bent against the thick stationary blade. The thick stationary blade holds the shorter flexible leaf in position.
In the next photo, a lane switch is properly adjusted. When the ball rolls through the out lane, the ball pushes a lever down against the switch. The long flexible leaf moves down and hits the short flexible leaf.
Because the short flexible leaf is bent against the heavy stationary blade, the two contacts can be adjusted close together without fear that machine activity will cause enough bouncing for the switch contacts to hit.
Adjusting the Switch Leafs
Generally, the leafs should only be bent with the leaf switch adjusting tool and the bending should only be done near where the ‘sandwich’ is located and held in place by the two screws. The rest of the leaf should remain unbent and straight – no curves or angles.
If there is a thick dampening stationary blade and a flexible leaf together, generally they are bent together.
When the flexible leaf is bent away from the thick stationary blade, it can be difficult to bend only the flexible blade. Try using your tool on the flexible leaf, only.
Here is a star rollover being adjusted for the proper distance from the long flexible leaf. Note that in this application, the long flexible leaf must be bent up as it is the ‘spring’ pushing up the roll over button.
Star roll over switches are particularly difficult to get right. The contacts have to be as close as possible so that a fast roll over by the pinball registers with the game. Using the thick stationary blade properly to set the gap, the two contacts can be quite close together without the switch ‘bouncing’ and causing false points.
Other Rollover Switch Adjustment
Rollover leaf switches have another component: the part above the playfield. When the pinball moves through a rollover, a small wire lever is pushed downwards against the leaf switch. If this is not adjusted properly, the leafs can be adjusted correctly, but the switch still does not activate.
It is pretty easy to use the switch adjustment tool to bend the wire so that it sticks up further into the playfield. But be careful as some of these are meant to allow the ball to move in either directly. If the wire is bent improperly, the pinball may not be able to move ‘against’ the switch.
The most difficult leaf switch to adjust properly are the pop bumper switches. Too close and the pop bumpers will activate without a pinball hitting it. Too far apart and a the game has a dead pop bumper.
First, clean the contacts. Then, most importantly, loosen the screws holding the switch and move the switch so that point coming down from the skirt is in the center of the ‘spoon’. If it is off center, the pop bumper will work when the ball hits one side of the pop bumper, but not the other. To make this easier to see, darken the end of the skirt point with a black sharpie.
Then adjust the switch in the same manner as the rollover switch.
Flipper EOS Switches
The flipper EOS switch is a leaf switch just like those above. Adjustment is similar.
[Click on the image for a larger picture.]
The first photo is a comparison to the Williams Fliptronics EOS switch to a standard EOS switch. Note that the contacts are not touching when at rest. This is known as ‘Normally Open’ or NO switch. The second switch is a standard EOS switch used by all standard flippers (non-computerized).
The second photo identifies the parts in the EOS switch. These are similar to the leaf switches used elsewhere in a pinball machine. The leafs should be adjusted so that the dampening stationary blade and short leaf are pushing against each other. The dampening blade holds the short leaf in position and keeps it from ‘swinging in the wind’.
The long leaf should be pushing firmly against the short leaf. There should be no situations where action during game play can cause these contacts to separate. The third photo shows the contacts make full contact while ‘at rest’.
When testing for the gap, it is better to push in on the plunger, rather than grab the flipper bat or the linkage. That is because, even with new flipper parts, there is a little bit of play in the linkage. Pushing the plunger into the coil will show the gap when the coil is activated.
The forth photo shows the plunger being pushed fully into the coil and the EOS switch gap. Note that the two contacts are apart, but not too far apart. If the contacts are further apart, then the switch opens too soon, which reduces power. If they are too close together, arcing can occur.
When releasing the plunger, hold it so that the two contacts are just touching (photo 5). Then observe what happens when you let go: the longer leaf should push back the shorter leaf just a little, insuring proper contact (photo 6).
Photo 7 shows the gap using a micrometer. This is overkill, but we did it just to show the size of the gap in the photo.
If adjustment is necessary, the dampening stationary blade and short leaf should be bent at their base. That will increase or decrease the gap when the flipper is activated. After adjusting, insure that the two blades are still pushing against each other.
For additional information, see the section on Rebuilding Flippers.
Stationary targets are another type of leaf switch. This one has two flexible leafs and two stationary blades. It is important that the flexible leafs be against the stationary blades to hold everything from bouncing.
Sometimes we find it easiest to adjust these switches by removing them from the playfield. But, on occasion, they are adjusted perfectly, but when reinserted into the playfield, the hole pushes the target back and causes the switch to be stuck closed.
Newer pinball machines have done away with most open leaf switches. These microswitches stay clean and are more reliable. However, they cannot easily be repaired or cleaned.
When they do not work, it is usually because the wire above the playfield is bent. That can be adjusted just like in the rollover switch (above).
If a microswitch does not work, it generally should be replaced (or maybe not – see note below).
When activating a microswitch, listen for a faint ‘click’. If not there, the microswitch might be broken. But the only certain test is to use a DVM and check resistance.
As with all non-working switches, a broken wire or open diode can also cause a failed switch and should be checked.
When ordering a new switch, sometimes it is possible to order the ‘naked’ switch and move the old switch attachment to the new one.
Here are two different micro switches. Both can be adjusted by bending the wire or tab coming off the switch with a switch adjusting tool.
The smaller of these two switches are commonly used in Stern ball troughs. Both of these switches are usually in a switch matrix and needs to have a diode installed.
Note: Michel_K17 has come up with a way of ‘fixing’ these switches that is an option, instead of replacing. This is great for those of us that just hate throwing stuff out. We have tried this fix, and it worked, for a while.
Diagnosing Problems with a Microswitch
If having problems with a microswitch, diagnosis of the issue is pretty straightforward:
* Locate the switch matrix in the service manual and find the switch number and the column / row in the matrix.
* Turn the game on to reset any drop targets. Turn the game off.
* Remove the pinballs and lift or slide out the playfield.
* Locate the microswitch.
* Turn the game back on and enter the service menu then the switch test. On DMD games, there should be a graphical matrix. With non-DMD games, there may just be a switch display number.
* Push the switch down and listen for the click. Make sure the switch lever is not bent so that the switch cannot open all the way. If no click, you can try cleaning the switch, but, generally, it will have to be replaced.
* If the switch clicks, but does not register, the switch could be broken. Or the diode could be open. Or a wire is broken. To test:
– Take a clip lead and connect it to the end of the diode that has the band. This side of the diode will not have a wire connected to it.
– Connect the other end to the tab that does not have a diode, but does have a wire connected to it.
– If the switch closes in the test menu, the switch is defective. If it does not, there is a problem with the switch matrix or the diode is open – test the diode. If multiple switches activate, then the diode is shorted, or you have connected the clip lead to the wrong side of the diode, or there is a problem with the switch matrix.
* If the switch is locked on, it maybe broken and require replacement. Or the wires could be shorted. Or there maybe a problem with the switch matrix.
Opto switches are switches are ‘electric eyes’ that use LEDs instead of a physical connection. In theory, they are more reliable. Unfortunately, they burn out and get dirty.
If an opto is not working, or if it is flaky and unreliable, it could be because it is dirty. Clean it with a Q-tip and isopropyl alcohol.
Most of the time, optos stop working because the transmitter (light source) burns out in a 20+ year old pinball machine. The optos used in Williams pinball machines are IR and not visible by the naked eye. However, it is possible to see if the transmitter is working if a camera can be aimed directly into the transmitter – not off to the side. Note: Some cell phone cameras can ‘see’ this IR light but others may not.
Data East/Sega/Stern pinball machines use optos that are visible to the naked eye.
Some Williams pinball machines use optos in the cabinet flipper switches. These can be cleaned for reliability.
These flipper opto switches can be replaced with leaf switches used in Williams Fliptronics games.
If replacing the opto assemblies, it is suggested to replace both the transmitter and receiver to insure that they are both on the same wavelength. It is also possible to purchase the raw LED from Great Plains Electronics (which, sadly, has been shut down), unsolder the burned out LED and solder in a new one (see below).
Note that the type of opto to use depends on the game. Bally / Williams WPC used QED123 for the transmitter and QSD124 for the receiver. DE/Sega/Stern used different raw optos and these are usually listed in the manual. These raw optos maybe purchased from Pinball Life, Marco, or electronics supply stores such as Newark.com, Mouser, or Digikey, sometimes for less than $1 each (plus shipping of course). We purchase ~100 at a time and replace every opto transmitter and receiver when we overhaul a 30 year old game.
Alignment may be an issue with optos. Sometimes it may be necessary to loosen the screws holding the optos and move them slightly to get optos to work.
Optos are usually plugged into separate opto boards usually located under the playfield. The opto board supplies power to the transmitter and converts the information from the receiver for use by the computer in the switch matrix.
‘U’ shaped opto housing are used in many specialty situations. These can include drop targets, the infamous Twilight Zone clock, as well as game specific mechanisms.
They are especially hard to clean because of the narrow slot, but usually a Q-tip with isopropyl alcohol can be squeezed in there. But usually, there is not an option other than to replace the board. The LED within the housing cannot be replaced. It maybe possible to obtain the LED/transmitter housing and replace that part on the board.
Fixing Non-working Optos
For most optos, there are two components that need to be working: 1) the transmitter and receiver, and 2) the opto board.
For the purposes here, we are going to focus on repair and replacement of the raw opto transmitter and receiver used in Williams / Bally WPC machines. The boards can be replaced, instead.
In most cases, it is wise to replace 20+ year old optos, even if they appear to be working. We recently completed a playfield replacement for a Williams WPC Indiana Jones. Since we had everything apart, we decided to replace all of the optos.
When replacing the optos, there are three options: 1) Replace the raw opto, 2) Replace the circuit board that holds the opto, or 3) replace the housing, circuit board and opto.
Option #1 is the least expensive. Raw optos, which are LEDs, are cheap. There are only two leads that must be unsoldered to remove it. The only trick is that they must be oriented in the proper direction (see photos below). For example, the Williams 6 or 7 ball trough opto boards are roughly $100.00. But the individual components (QED123 for the transmitter, and QSD124 for the receiver on most WPC pins) are only $0.65 – $1.00 or so each. So the transmitters and receivers can all be replaced for less than $12.00. And, if you are really feeling lucky, try replacing just the transmitters for $6.00 or less.
Not all raw optos are readily available, so you may have to do a little searching to come up with those that are more difficult to find.
We went the small circuit board route. At $2.25 each or $4.00 for a pair, that is a small penalty vs. the $0.40 x 2 for the raw components. But we saved the old boards and installed new raw LEDs in them for parts.
It is crucial to insure that the same wire is connected to the same position (see ‘Positioning to Move Wires’, above). We remove the old board, install the new one, then solder the wires one at a time to check that they are soldered to the right place. The transmitter have pads clearly marked ‘K’ and ‘A’, while the receiver has pads marked ‘E’ and ‘C’.
Replacing the Raw Optos
Replacing the raw optos, the LED and photo transistor located on each board is easy.
The leads are close together, so just touch both at the same time with a hot soldering iron and lift out the old opto. Then clean out the holes, usually with a solder sucker, until the holes are completely clear.
Insert the new ones (see the photos for the correct orientation), solder and then clip off the leads. All done.
Note that the darker opto is the photo transistor – the receiver. This is the Williams WPC opto receiver board and a replacement is QSD124, a NPN Infrared Phototransistor. In the original board, there is a drawing of a ‘tab’. The raw transistor we received do not have a tab. Instead, it has a flat side. The flat side is the shorter ‘E’ lead which should be positioned towards the ‘tab’ on the board. As far as we can tell, all QSD124 photo transistors have the same lead orientation.
As of early 2022, Pinball Life sells a similar replacement photo transistor, but the lead orientation is the opposite of the QSD124 (Pinball Life said they were going to discontinue this specific part). And both leads are the same length. This may change. Marco responded that they did not have a Datasheet to determine lead orientation.
The lighter color is the transmitter QED123 infrared LED used in the Williams WPC optos. It has a flat side. The flat side matches up with the board flat side drawing. The shorter lead, ‘K’ (cathode), goes into the left hand hole.
Note: It is crucial that the new opto & receiver be installed perfectly flat to the board, or they may not align. Since this can take three hands, we usually solder one lead. Then we go back and reheat that one lead while pushing the LED flat against the board, holding it there until the solder cools.
This is the same procedure for ball trough opto boards, except that there are several transmitters on one board, and the same number of receivers on the other. While it is the best idea to replace both the transmitters and receivers, we frequently try to cheat and just replace the transmitters. If that does not work, then go back and replace the receivers.
Note that other games, such as DE/Sega/Stern use different optos and their leads might be different orientation, especially for the photo transistor. For example, some Stern, Sega and DE optos are MV8114 (equivalent to MT5000UR and TLRH180P) which is used for both the transmitter and receiver. This part is obsolete and getting harder to find.
There is a service bulletin on the operation of the DE/Sega/Stern optos. Replacing the raw optos is the same procedure as replacing those in WPC pins, except that the transmitter and receiver are the same MV8114 part.
Some games use ‘slotted’ optos. Those have the transmitter and receiver in the same housing and must be replaced together. The slotted optos used in some WPC games (the QVE11233.0086) have different dimensions and higher current capabilities and maybe difficult to find. However, DE/Sega/Stern slotted optos can be relatively easy to find. These are also used on some Williams boards.
If the correct part can be located, replacement is fairly easy and far cheaper than a new board. Note that four leads will have to be unsoldered and, once again, correct orientation is crucial. And it must be installed perfectly flat against the board.
For those wanting detailed technical information on the Williams slotted optos (notably used in the Twilight Zone clock), please see this excellent thread.
Reed or Eddy Switch
A few games use a reed or eddy switch. It is a box that is magnetic and senses the iron in a pinball. They are completely sealed. Other than checking the wiring and plug, there is nothing that can be done to clean or repair these switches. These switches are becoming difficult to find, and can be expensive when available.
Comments, including suggestions, improvements, errors, etc. are welcome (see below).
If you have a specific question about your game that does not directly apply to adjusting switches, please see our FAQ section.