Molex Connectors Explained,
as used in Pinball.
04/03/05 - by email@example.com.
Information gathered from Molex.com, talking to
Molex technical advisors, and [name removed by request] (an eight year automotive wiring industry
Manufacturing Engineer, who worked for three years as supervisor of the wiring crimp die
engineering department and four years as the Program Manager of a Vehicle Wiring Program
for an automotive wiring company in Detroit).
Most pictures by Molex.
Table of Contents.
- Connectors Explained (Introduction)
- When are Connectors Worn Out?
- Connector Tools & Parts Needed, and Where to Get Them
- How to Perform a Good Connector Crimp
- Should Connector Terminal Pins be Soldered?
- Converting Looped IDC Terminal Pins to Crimped Pins
- Removing Connector Terminal Pins
1. Connector Introduction.
Why Use Connectors?
You don't need a connector to complete a circuit. You could solder
components together. However, imagine the effect soldering would have on
assembly manufacturer, repair and upgrades.
Using connectors offers several important advantages over permanent connections.
Connectors improve manufacturing:
Connectors make it easier to assemble electronic products. They also facilitate mass
Connectors ease repairs:
If an electronic component fails, connectors allow a technician to quickly
replace it with a new one.
Connectors permit upgrades:
As technology advances, connectors allow us to replace old components with
newer, more sophisticated ones.
Connectors allow design flexibility:
Connectors give engineers the flexibility to design and integrate new
products and components into existing systems.
Usually made of molded plastic, a housing is a connector's casing. Its main
functions are to hold the terminals and protect them from shorting, dust, dirt, moisture,
and electrical interference.
Terminals are the metal components in a connector that conduct current. They
are also known as contacts, and they are usually either male or female,
as shown on the right. You may hear certain types of male terminals referred
to as leads or posts.
Terminals are inserted into connector housings. When the connectors mate,
the terminals meet and bridge the circuit path.
Methods of Termination.
Termination is a key concept in connector design. It refers to the method
used to join a terminal and a conductor. Good termination assures sound
electrical contact and maximum strength between the conductor and the terminal
(for a gas-tight connection, to prohibit corrosion).
The most common termination methods are listed on the right and discussed
on the next few pages
- Crimping: What all replacement pinball connectors should use. Also utilized
by many others, especially the auto industry.
- Insulation displacement: What many pinball manufacturers originally used.
- Surface mount: hi-tech electronics industry.
- Wire wrap: for prototyping.
- Press fit.
In crimping, a metal sleeve is secured to a conductor by mechanically crimping
the sleeve with pliers, presses, or automated crimping machines.
Note that the conductor is crimped in two places – on the wire and on its
insulator. The latter is called a strain relief. It provides additional resistance
to mechanical stress. A "good crimp" provides a gas-tight connection on
the terminal pin, which prohibits corrosion at the wire to terminal pin
connection. Since a crimped connection can be easily performed with an
inexpensive hand crimper, and provides an excellent gas-tight connection,
this is what should be used on most replacement pinball applications.
Crimped connectors also work well in a production environment. Molex
makes automatic crimping tools and dies, which can feed terminal pins
and wires, doing many many crimps automatically per minute.
After talking to the
Molex tech advisors, they admitted this:
"Hand crimpers are a necessary evil. We don't like
them, and wish we didn't have to sell them. They can
provide inconsistent crimps, with the possibility
of human error. And they can make our highly engineered
products fail when they should not fail, if machine
installed." So keep that in mind when hand crimping!
The end result is all up to you (below is a guide to
proper hand crimping.
In insulation displacement technology (IDT or IDC), an insulated wire is pressed into a
terminal slot smaller than the conductor diameter, displacing the insulation
to make electrical contact.
In application, insulation need not
be removed, which is a major advantage of this method of termination using
Insulation Displacement Connectors (IDC). That is, the advantage to IDC connectors
is that assembly time is dramatically reduced, decreases cost.
This is why most pinball manufacturers
used this (crappy!) style of connector termination originally.
IDC connectos are not used for reliability, they are used to decrease assembly cost.
Hence as a replacement, this style connector should be avoided.
IDT/IDC connectors are great for manufacturers. There's no separate step of stripping
the wire for connection to the terminal pin, and no crimping step.
Basically the only connection step
involved is mating the wire to the IDT connector and pressing it in place.
In the short time, an IDT connector works fine. But over time, due to the design
of IDCs, the "V" that cuts through the wire insulation can also eventually cut the wire strands
too (causing a decrease in current handling, which means a burnt connector!)
Also the wires can be pulled/ripped from the IDC terminal pin much easier than a crimped
connection. And lastly, the tool required to do a good non-production IDT connection is expensive,
compared to a hand crimper (I'm not talking about that small IDC mushroomed shaped tool).
IDT/IDC versus Crimped Connector Current (Power) Ratings.
Molex and Panduit (Panduit was used by Williams Electronics on their WPC pinballs) IDC connectors
are rated at 7 amps and 8 amps respectively with 18 gauge wire.
But this rating is for 20 degrees C (68 degrees F).
At 25 degrees C (room temperature), they are rated at 7.5 amps.
And current capabilities drop fast as the temperature increases.
Most electronic pinballs operate at least at room temperature, and usually
much warmer. At 60 degrees C they are rated at 4.5 amps.
At 75 degrees C they are rated at less than 4 amps.
Why does current capability drop off so quickly? The contact to wire
connection is the problem. The IDC contact to wire is
four small surface area positions, and this leaves no room for thermal
expansion. (Compare this to the contact to pin connection, which
is only slightly affected by thermal expansion.)
Now look at crimp-on connector. These are rated at 7 amps, but
they will handle 7 amps all the way to 75 degrees C.
Crimp-on connectors do not have the contact to wire thermal expansion
problem that the IDC contacts have.
Note crimped Molex Trifurcon connectors do not handle any more current.
But they do have a big advantage - they are much more vibration resistant,
and maintain their current handling much better than single wiper connectors.
Pitch is the distance from center-to-center between adjacent conductors.
Pitch also affects arcing, which can cause interference
between adjacent conductors in a connector. The most common pitch size used
in pinball is .100" (for low voltage data) and .156" (for power connections).
There are many types of connectors. However, each type fits into one (or more)
of five categories. In the industry, these categories are known as levels.
The levels were defined by major connector companies under the auspices of
an organization called NEDA.
- Wire-to-Board or Subassembly-to-Subassembly Level (common pinball usage).
- Box-to-Box or Input/Output Level (also used to a lesser degree in pinball).
- IC Chip or Chip-to-Package Level.
- IC Package or Package-to-Board Level.
- PC Board-to-Board Level.
Signal and Power Connectors.
There are two broad types of connectors: signal and power. They are often
distinguished by the amount of power they carry. But the key distinction is
that signal connectors have minimal resistance to current flow. This minimizes
disruption of the relatively weak signals flowing through them.
A disk drive uses both signal and power connectors. The power connector bridges
the circuit that drives the unit. Because the power current is so strong, a small
loss is acceptable. The signal connector, however, carries data in very weak
signals. The connector is therefore designed to eliminate signal loss.
Conductors and Insulators.
Electrical charge moves through some materials better than others. Substances
through which electrons flow freely are called conductors. Substances that
resist the flow of electrons are called insulators. In the electronics
industry, a more common term for insulator is dielectric.
Copper wire is an excellent conductor because it has a large number of
free electrons. If a copper wire is connected between the terminals of
a battery, free electrons in the wire move from the negative terminal to
the positive terminal. This free flow of electrons is electric current.
Terminals as Conductors.
In a connector, current is conducted through the connector by the contacts
or terminals, which are made from various metals. Metal is one of nature's
best conductors because it has a lot of free electrons. When two metal
terminals mate, electrons can flow from one surface to the other, continuing
Insulators in Connectors.
Plastics are used in connector housings because of their excellent dielectric
properties. Like all good insulators, plastic resists the flow of electric
current. The electrons of an insulator are tightly bound to their atoms and
cannot move freely, even if you apply an external charge.
Other common insulators are glass and rubber.
Voltage is a force that pushes electric current through a circuit. It causes
electrons to jump from one atom to another. Voltage is often referred to as
electric pressure, and is indicated by the V symbol. Typical connector voltages
are 50V, 125V, 250V, and 600V.
This dammed river image is often used to explain electrical measurements. Voltage
is like water pressure. No force actually pushes electrons through a circuit.
Rather, like the water level, the difference between the two levels forces the
flow. The greater the discrepancy between levels, the greater the flow.
Current Rating and Amperage.
Current rating indicates the rate of flow of electricity. It is measured in amperes
and is indicated by the letter A.
In a connector specification, this figure indicates the maximum amperes at which
the connector can be used continuously without electrical or mechanical failure.
Amperage is similar to gallons per minute or gallons per second. It indicates
how much electric current flows past a certain point in a given time period.
Connector current ratings are usually in the range of 1A to 50A per circuit.
Resistance and Ohms.
Resistance is a material's tendency to inhibit electron flow. Resistance is
measured in ohms.
This specification indicates the maximum resistance of the contact area when
the connector is mated. Typically, this is less than 25 milliohms.
In the water example, resistance is caused by the valve. Tighten the valve and the
rate of flow decreases. In a conductor, resistance is a property of the material.
It occurs when electrons collide with atoms and give up energy. A conductor
like copper has low resistance.
The Relationship between Voltage, Resistance, and Current.
It's important to understand that voltage, resistance, and current are not
independent of each other. They have an intimate relationship. Their
relationship is expressed by Ohm's Law.
When selecting a connector, all three must be considered and matched to the application.
Ohm's Law: the current in an electrical circuit is directly
proportional to the voltage and inversely proportional to the
resistance. Voltage = Current x Resistance, or Current = Voltage/Resistance.
The important point about Ohm's Law is that, when selecting connectors, all
the electrical specifications must be considered. All metals have inherent
resistance. The greater the resistance, the more voltage is required to push
the current through the connector. Using Ohm's Law we can determine the
overall efficiency of a connector.
Mechanical Specifications of Connectors.
The mechanical specifications of a connector indicate how a connector
performs under critical mechanical actions. These are of great
importance to customers who must match the right connector to an
Contact Insertion Force.
This specification identifies the mechanical force required to
insert a terminal into a connector housing.
Contact Retention to Housing.
Contact retention force holds a terminal in a housing cavity. This
prevents terminal backout, or the coming loose of the terminal.
Typically, locking devices called tangs secure the terminal
against the housing walls using spring-like pressure. The contact
retention to housing specification describes the force required to
remove a properly seated terminal.
Wire Pull-Out Force.
This specification describes the force required to separate a
wire from a terminal by pulling them apart. This is primarily
a function of the termination method and the quality of the
termination. In a crimped terminal, for example, both the
insulation and conductor are crimped to assure maximum wire
Mating and Unmating Force.
This specification describes the force required to join and
separate two halves of a connector. This is the sum of contact
mating forces plus any additional force necessary to overcome
minor misalignment of connector halves and any dimensional
variations in the housings.
Once terminals are mated, normal force is the pressure applied
perpendicular to the terminal interface. This pressure assures
a gas tight condition between the terminal surfaces. This is
considered the most important mechanical specification because
it assures a consistent and high quality electrical contact.
Durability of Terminal Pins and Header Pins.
Durability indicates the number of times a terminal can be mated and unmated
without degrading performance. Durability is measured in "cycles" (the number
of times a connector can be removed or installed).
As shown above, durability varies with the materials used.
The typical pinball connector (tin plated) has a life of 25 cycles. That's pretty
low! But after 25 insertions or removals, the terminal pin's plating and
retention (ability to retain shape) are compromised, and reliability will
suffer. Header pins also have the same problem with plating
(but not retention!) Add vibration into the formula, and the cycle life is probably
If pinball manufacturers had used gold plated parts, the terminal
pin life would be up around 100 cycles. But gold parts cost more, and
pinball machines have an expectant operating life of five years (having a longer
life than five years could limit sales of future games!)
This is the reason why cheaper "25 cycle" terminal pins are used by pinball
makers. Connectors are probably
the biggest single problem in solidstate pinball machines (of any pinball
manufacturer). So in a way, shorter connector life is a "built-in timer" to
limit the reliable life of electronic pinball games, hence keeping operators
from profitable running a pinball machine for greater than five years.
If a pinball machine is over five years old, chances are *really* good
it will need at least some connector replacement! If the General Illumination
(GI) 6 volt connectors are not burnt, chances are good they have been stressed. Also
the power connectors handling the +5 volt logic and +12 volts probably need
some attention too. There are really no exceptions to this rule! If a game
is to run reliably, replacing these connectors (at minimum) will probably be
needed. If a game is even older than five years, I can almost guarentee
the user will be doing some sort of repair to the connectors. It's just
a matter of time.
Terminals and pins are made of a variety of metals, each with
different properties. Because of their atomic structure, metals
are excellent conductors of electricity. Metals also have
mechanical properties that make them ideal for connector terminals.
The properties of metals that are of interest to connector
- Electrical conductivity
- Mechanical strength
- Resilience (ability to return to its original
shape after slight deformation)
Common Metals Used in Molex Terminals
||Zinc content varies from 5-40%
Cheapest metal by weight
Molex standard metal is 70/30 copper/zinc
Good spring, strength and electrical properties
|Good strength, toughness, conductibility
Excellent fatigue resistance
|Electrical contact springs
|Finest copper alloy for spring terminals
Increasingly used by Molex
Price significantly better than phosphor bronze
|Applications demanding optimum performance
|High Copper Alloy
||High strength modified copper
Good thermal and electrical properties
Resists softening at high temperatures
|Mainly automotive applications
Metals that have good mechanical properties do not always have ideal
electrical properties. Plating is the process of coating terminals of
base metal with a layer of nickel, tin, or gold to improve their electrical
Common stamping metals include brass, phosphor bronze, beryllium
copper, and other copper-based alloys. As you have learned,
these metals have good strength, spring, and formability.
Yet each of these metals has electrical deficiencies. To
overcome these deficiencies, terminals made from them are
plated with gold, tin and tin-based alloys, and palladium/nickel
Copper-based alloys have ideal mechanical properties, but they
do not meet other connector design requirements. They are plated
- Electrical performance
- Corrosion protection
Most pinball connector pins are made of brass. But phosphor bronze
is a better choice for power circuits like General Illumination
(if available in the pin desired), as it has higher current rating.
Beryllium copper is also good, but often not available for the terminal
For example, for .156" trifurcon terminal pins series 6838, here is
a comparison of brass versus phospher bronze current (amp) ratings:
Trifurcon Terminal Pins.
The Trifurcon design provides three distinct points of contact from the
terminal pin (above left) to the header pin (above right). This is the
ideal choice where high shock or vibration exists.
For low current/voltage, Gold is recommended (contact factory).
Phosphor Bronze recommended for higher rated current circuits.
Trifurcon only available for .156" and larger pitch.
Because Trifurcon connectors resist vibration, they maintain
their current (power) ratings much better than single wiper connectors.
For this reason Trifurcon crimped connectors are ideal for pinball applications.
Plating and Corrosion.
Recall that corrosion is the deterioration of a metal due to exposure to moisture
or other contaminants. This is a key concern of connector designers. If voltage
or wiping pressure is high, a corrosive layer is easily penetrated. But in low
voltage situations, even slight corrosion can obstruct current flow. Plating
materials such as gold are chosen for their high resistance to corrosion.
Metals vary in their resistance to corrosion. The relative corrosion resistance
of different metals varies, from aluminum, which corrodes easily, to gold, which
does not corrode at all. The list below shows from top to bottom, metals which
corrode easily (1) to metals that do not corrode at all (10):
||Overall, excellent terminal finish
Most widely used plating material
Low durability and corrosion resistance
||Excellent corrosion resistance
Soft, but cobalt or nickel are added to harden
Selective plating reduces cost
|Palladium/ nickel alloy
||Less expensive alternative to gold
Considered the best substitute for gold
Improves cycle life
Tin versus Gold Plating.
Terminals plated with tin or tin alloys oxidize and are contaminated by gasses,
water vapor, and organic molecules. This film degrades conductivity, so
sufficient wiping pressure must be applied to break the film. This pressure
also removes tin plating, which decreases durability. Gold Plating
Oxide film does not form on gold, so wiping pressure can be lighter to
penetrate only the contaminants. Durability is much higher, often in the
hundreds of cycles. This is why modular phone jack terminals, which may
be mated and unmated many times, are usually gold plated.
Selective Gold Plating.
The process used to plate gold only in selected areas of a terminal.
Selective plating assures that critical terminal areas are plated, but
non-critical areas are not. This reduces costs.
Do NOT Mix Gold and Tin Terminals and Headers!
It is not a good idea to mate a gold terminal to a tin header (or vice versa),
or mix any other dissimilar connector metals.
Use the same metal for both contacts! The contact resistance will go up with
dissimilar metals, causing all sorts of problems (depending if it is a
logic connector or power connector). This exact problem has
been seen in the automotive industry. Though no cars have been recalled
because of this (that I know of), there have been numerous "engineering
actions" and "service bulletins" because connectors have mixed gold and
2. When are Connectors Worn Out?
Failing connectors can cause a great number of problems in
solidstate pinball games (1977 to present). For example, random
game resets (where the game seemingly turns itself off and
back on during a game), game lock-ups, coils and switches and lamps that
don't work, and other random and
unpredictable behavior are largely attributed to failing connectors.
Re-Seating Connectors - the False Hope.
A good many pinball people will try and "fix" these problems
by doing a connector "re-seat". That is, they will remove
and reinstall the questionable connector in an attempt to
"fix" the problem. Unfortunately, this does *not* fix the problem!
Connector re-seating is a great way to identify a connector problem.
If the problem goes away with a "re-seat", that means the connector
needs to be replaced.
But the re-seat itself does not fix the problem. The only way to fix
the problem reliably is to replace all the connector parts
The Five Year Life Span.
The style of Panduit and Molex connectors used in pinball
generally have a 25 "cycle" life
span (a "cycle" is one removal and re-installation of a
connector). And frankly, after as few as five cycles, there
could be problems because of the high vibration pinball
environment, the reduced terminal pin tension,
and the age of many games. Frankly, these connectors, chip sockets,
and the games themselves were only manufactured
to have a five year life span. This was done (intentionally
or unintentionally) by the manufacturer
to ensure the games "broke" (or became a unreliable,
i.e. a "pain in the butt") after five year, so operators would buy
new games. This is call "planned obsolence", or "job security" for
the amusement industry. Because successful games that earned well
and didn't break for more than five years were *hated* by the
industry that created them!
Re-Seating Five Times to "Clean".
The other false "repair tip" heard among many
repair people is to "reseat a solidstate connector five times
to 'clean' it". This is not only a bad idea, but
it just makes things worse (because it eats up
five cycles in the connector's already short 25 cyle life
span). Again the reseat priniciple is great at IDENTIFYING a
connector problem, but it does NOT fix anything!
The except to the reseat rule involved gold plated
connectors. These have a much lower terminal pin
tension, and a higher 100 cycle life. In the case of
gold connectors, the "re-seat to clean/fix" is acceptable.
But gold connectors are rarely used in pinball
(ribbon cables are the only gold plated connectors
used in pinball).
But if the connector in question is a .156" or .100" Molex connector,
I don't care how old/new the game is, if re-seating
"fixes" the problem, that connector needs to be
replaced! No if's, and's, or but's.
Gas Tight Seal.
For a connector or socket to be reliable, it *must* have a
"gas tight" seal (air tight, but the connector industry
calls it "gas tight").
In the situation of pinball, nearly all connectors/sockets
are tin on tin. To keep tin on tin gas tight, a fair amount
of terminal pin tension is required against the male
pin. The amount of tension needed has to do with
the corrosion properties and wear properties of tin.
If the gas tight seal is compromised on a tin on tin
connector/socket, corrosion works on the junction, and
an intermittent connection is the result. This corrosion
is usually the result of either:
- Decreased pin pressure (too many cycles and/or too much
- Worn parts (the tin plating is worn from too many cycles
and/or too much vibration, and does not protect
against corrosion like it once did).
Reseating does NOT fix the lack of a gas tight seal on
tin on tin connectors or sockets! If corrosion has started,
re-seating does not fix this. All it does is temporarily
"fix" it, until corrosion comes back (and it WILL come
back!) A connector/socket that works after re-seating is telling the
repair person something ("replace me!") My suggestion is
to listen to the game.
3. Connector Tools & Parts Needed, and Where to Get Them.
I can't think of any solidstate 1977 or later pinball machines that I have
worked on that have not needed some sort of connector repair! With this in
mind, certain tools and parts should be in every pinball mechanic's toolbox to make
the job better and easier (no, needlenose pliers can *not* be used to
crimp connectors!) There's no cheap way to do this. The right tools
and parts are needed, so just honker down and buy them.
Here are the minimum connector tools required.
- Terminal Pin Hand crimper. These are used for all the different styles of
Molex terminal pins.
- Aeroelectric's terminal tool BCT-1, available from
(about $32, good for all pin sizes) is an excellent crimper,
- Molex crimper #11-01-0185 (type 1 specifically designed for .100" terminal pins, 22-30 guage wire).
- Molex crimper #63811-2200 (type 1 specifically designed for .156" terminal pins, 18-24 guage wire).
- Molex crimper #63811-1000 (type 6, inexpensive but versatile, 14-24 guage wire).
- Molex crimper #11-01-0015 (type 3, excellent but more expensive, 18-24 gauge wire, discontinued).
- Waldom/Molex crimper WHT-1921 (good yet inexpensive, for .100"/.062" and .156"/.093" pins).
- Waldom/Molex crimper WHT-1919 (really for .156"/.093" pins only).
- Amp 725 (probably no longer available).
- Radio Shack #64-410 (last resort, not very good and not recommended).
- .093" Round Pin Extractor:
Molex part number 11-03-0006, or
Waldom/Molex part number WHT-2038, or
Radio Shacks part number 274-223 (in this case the Radio Shack tool is
- .062" Round Pin Extractor:
Molex part number 11-03-0002, or Waldom/Molex #WHT-2285.
Optional, as this size is not used nearly as much as the .093" size.
- .156" terminal pin extraction tool from card edge connector housings:
Used mostly for Gottlieb system80 games.
Made of spring steel, Molex part number
11-03-0016 (rubber handle version),
or Molex #11-03-0003 (bare bones version).
The BCT-1 hand crimper's different jaw sizes for |
different size connector pins. The "C", "D", and "E"
pockets are used to crimp the bare wire to the Molex
connector pin. These pockets cause the end of the
pin's wire grip wings to curl over and dive into the
center of the wire strands. Pockets "A" and "B" have
a smooth circular shape, and can be used to crimp the
terminal pin's insulation-grips into a "bear hug"
around the wire's insulation, but Molex suggests using
the C,D,E pockets for insulation too. Picture by aeroelectric.com
Left: Molex/Waldom .093" pin extractor #WHT-2038.|
Middle: Radio Shack .093" pin extractor #274-223.
Left: Molex spring steel card edge extractor #11-03-0003.
Molex Connector Parts to Keep On-Hand for Pinball Applications.
The following are standard Molex connector parts commonly
used in pinball machines. Panduit connectors can also be used, but
they are very hard to find and more expensive. Note there are some game specific
Molex connectors (such as Gottlieb system80 double sided edge
connectors, and Williams system3 to system7 interboard connectors)
that are not listed here, because they are specific to only those
games. The parts below are used in nearly every solidstate pinball
machine. All the below terminal pins and housings are the crimp-on variety.
If the game being repaired uses IDC connectors, to utilize the more
robust crimp-on connectors, the plastic housing
will probably need to be replaced in addition to the housing terminal pins
and male circuit board header pins. If you want to buy a minimum of parts,
buy the largest header and housing sizes available and cut to the size needed.
- .156" header pins Molex #26-48-1155 (15 pin, with lock, cut to size).
- .156" plastic housings Molex #09-50-3151 (15 pins).
- or .156" plastic housings Molex #26-03-4151 (15 pins).
This particular housing is less expensive, and specially designed for Trifurcon
- .156" plastic housing polarizing pins Molex #15-04-0219.
- .156" Trifurcon connector terminal pins Molex #08-52-0113 (the replacement pin of
choice, used extensively in pinball; buy lots of these). Phoshor Bronze material.
- .156" connector terminal pins Molex #08-52-0072 (non-Trifurcon, used far less often and
not as good as Trifurcon, but still needed in some situations). Only buy these as needed.
* bold text denotes the number of pins, in this case, 15.
- .100" header male pins Molex # 22-23-2121 (12 pins, with lock, cut to size).
- .100" plastic housings Molex # 22-01-3127 (12 pins, cut to size).
- .100" plastic housing polarized pin Molex # 15-04-9210.
- .100" terminal pins Molex # 08-50-0114.
* bold text denotes the number of pins, in this case, 12.
- .093" round female terminal pins Molex #02-09-1119.
- .093" round male terminal pins Molex #02-09-2118.
Where to Buy This Stuff.
All the above Molex connector parts are available from
the retailer listed at the
parts and repair sources web page.
Note for Mouser part
number (which can be viewed/ordered on Mouser's web page),
just add a "538-" before the Molex part number listed above
(for example, "538-08-52-0113" is the Mouser part number for
Trifurcon Molex terminal pins, as "538" is Mouser's
manufacturer number for Molex). The above
connector parts are also available from other source.
Check out the
parts & repair sources web page for details.
4. How to Perform a Good Connector Crimp.
re-edited, modified, and embelished with emphasis on hand crimping and pinball applications.
All pictures from Molex.
You've made it through all the pinball and connector manuals, and found the replacement
connector that meets your pinball's application.
It has the right current rating, voltage
rating, circuit size, pin size, engagement force, wire AWG capabilities,
configurations, termination method,
positive locks, fully-isolated contacts, and polarization,
it is the perfect replacement connector.
But don't let out a huge sigh of relief quite yet - especially
if the connector chosen uses a crimp termination system.
While this can be one of the fastest, most reliable and rugged
termination methods, if the terminal isn't crimped onto the wire
correctly you can forget all about the hard work put into
finding the right connector. Although there are many common
crimping problems that can reduce the reliability of a
pinball machine, these problems are easy to avoid with a little
knowledge and advance planning.
The BCT-1 hand crimper for crimping Molex connector pins.|
Picture by aeroelectric.com
Before proceeding, you'll need some sort of hand crimper.
Several hand crimpers are available from Molex and other sources.
See the section above for details on that.
But now that you have the proper hand crimping too, it's time
to talk about how to use it properely to make a "good crimp".
To begin with, it helps to understand that a terminal has three
major sections: Mating, Transition and Crimping.
An example of a properly performed crimp is seen below:
The Mating section, as the name implies, is the section of
the terminal that mates, or becomes the interface, with the
other half of the connection. This section was designed to mate
with a terminal of the opposite gender and to perform in a
certain manner by the connector design engineer. Anything done
that deforms the Mating Section, especially during the
crimping process, will only reduce the connector's performance.
The Transition Section is also designed so not
affected by the crimping process. Here again, anything done
that changes the position of the Locking Tangs or Terminal Stop
affects the connector's performance.
The Crimp Section is the only section that the crimping process
is designed to affect. Using a good quality hand crimper,
the crimp section is deformed so
it can be securely attached to a wire. Ideally, all the work
done to crimp a terminal onto a wire occurs only in the
In the picture above, the insulation crimp compresses the insulation without
piercing. The wire strands (or brush) protrude through
the front of the conductor crimp section by at least the
diameter of the wire's conductor. For example, an 18 AWG wire
would protrude at least .040". Both the insulation and conductor
are visible in the area between the insulation and the conductor
Crimp Section. The conductor Crimp Section shows a bellmouth
shape in the leading and trailing ends, while the Transition and
Mating Sections remain exactly the same as they were before the
If a crimped terminal does not look like the terminal in
the above illustration, the problem was probably caused by something
that went wrong during the crimping process. Below are the
most common problems that may occur during the crimping process,
and how to avoid them.
Crimp Height is Too Small.
The crimp height, which is the cross sectional height of the
conductor Crimp Section after it has been crimped, is the most
important characteristic of a good crimp. The connector
manufacturer provides the crimp height for each wire size for
which the terminal was designed. The correct crimp height range
or tolerance for a given wire may be as small as 0.002".
With a specification this tight, getting a perfect hand crimp
can be difficult. And forget measuring the crimp height;
terminal geeks would measure this with a "point micrometer",
something I can guarentee you don't have in your pinball
But still, the information is good to know. So keep in mind that
an over-crimped terminal (crimp height too small) is just as bad
as an under-crimped (crimp height too large) terminal.
A crimp height that is either too small or too large
will not provide the specified crimp strength
(terminal retention to the wire), will reduce the wire pull out
force and current rating, and may generally cause the crimp to under
perform in otherwise normal operating conditions. A crimp height
that is too small also may cut strands of the wire or fracture
the metal of the conductor crimp section.
Crimp Height Too Large.
A crimp height that is too large will not compress the wire
strands properly. This causes excessive voids in the Crimp Section
because there is not enough metal-to-metal contact between the
wire strands and the metal of the terminal. This also compromises
the Gas Tight seal that a good crimp offers.
The solution to problems the above problems is very simple: adjust the
conductor crimp height. With a hand crimper,
either press harder or lighter to adjust the crimp. Also make
sure the right crimper is being used (remember there is a different
hand crimper for .100" and .156" terminal pins).
Crimp width is just as important as crimp height. For optimum crimp
performance, the cross sectional area needs to controlled. For the most
part, the crimp tool geometry will produce the proper crimp width, when
the terminal is crimped to the recommended height. This assumes you're
using the manufactures recommended crimp tool. If using a different
crimp tool, the width may be incorrect. Therefore, the
resultant cross section will be too large or too small.
So what's the bottom line here? Buy a Molex (or Waldom) hand crimper
designed for .156" or .100" terminal pins. This will ensure a
better hand crimp.
Insulation Crimp Too Small or Too Large.
Connector manufacturers do not typically supply a crimp height
for the insulation due to the variety of insulation types and
thicknesses. The insulation crimp provides a strain relief for
the conductor Crimp Section so that as the wire flexes, the wire
strands do not break. An insulation crimp section that is too
small may overstress the metal in the insulation Crimp Section,
weakening the strain relief function (and potentially breaking the wire).
Most types of production crimp tooling allow the insulation crimp height to
be adjusted independently of the conductor crimp height. The correct adjustment allows
the terminal to grip the insulation for at least 180 degrees
without piercing the insulation. An insulation displacement, or
compression where the outside diameter (OD) of the terminal's insulation crimp and
the OD of the insulation are approximately the same, is ideal.
Loose Wire Strands
Loose wire strands are another common cause of crimping problems. If all
the wire strands are not fully enclosed in the conductor Crimp
Section, both the strength of the
crimp and the current carrying capability may be greatly
reduced. To get a good crimp you need to meet the crimp height
the connector manufacturer specifies. If all the strands are not
contributing to that crimp height and therefore crimp strength,
the crimp will not perform to specifications. Generally,
the problem of loose wire strands is very easy to solve by
simply gathering the wires back into a bunch before inserting
them into the terminal to be crimped.
Using a "strip and retain" process for insulaton
removal, where the insulation slug is not completely removed
from the wire until it is ready to have a terminal crimped onto
the wire, helps minimize the problem (yea right, now who does that?)
Too Short Strip Length
If the strip length is too short or if a wire is not fully
inserted into the conductor Crimp Section, the termination may
not meet the specified pull force because the metal-to-metal
contact between the wire and the terminal pin is reduced. As shown
in the figure above, the strip length of the wire is too short (note
that the insulation is in its proper position), not allowing the
required one wire outside diameter (OD) extension in front of the conductor Crimp
Section. The solution is simple: increase the strip length of
the wire stripping equipment to that specified for that specific
Wire Inserted Too Far
Another crimping problem that relates to a too short strip
length occurs when the wire is inserted too far into the crimp
sections. As the figure above shows, the insulation is too far forward
of the insulation Crimp Section and the conductors protrude into
the Transition Section. This may cause as many as three failure
modes in the actual application. Two relate to a reduced current
rating/wire pull out force due to a reduction of the metal-to-
metal contact in the conductor Crimp Section. A metal-to-plastic
contact isn't as strong, nor does it conduct electricity, as
well as metal-to-metal.
The third failure mode may occur when the
connectors are mated. If the wire protrudes so far into the
Transition Section that the tip of the male terminal hits
against the wire, it may prevent the connectors from fully
seating or it may bend the male or female terminals. This
condition is known as "terminal butting".
Under extreme cases, the terminal may be pushed
out the back of the housing even though
it was fully seated in the housing.
"Banana" (Excessive Bending) Terminal
One of the most descriptive crimping problems is known as a
"banana" crimp (figure above), because the crimped terminal takes
on a banana shape. This makes it difficult to insert the
terminal into the housing and may cause terminal butting. This
problem is easy to solve by not squeezing the hand crimper so hard!
Crimp Too Far Forward
One of the more obvious crimping problems is when part of the
Transition Section is
damaged, as shown above. In the terminal shown, the tab
sticking up is a design feature called a "terminal stop". Its
function is to prevent the terminal from being inserted too
deeply into the housing. If the stop is extremely damaged, the
terminal can actually be pushed all the way through the housing.
The correct size for a bellmouth (see above) is approximately 2X
the thickness of the terminal material. For example if the
terminal is made from material that is .008" thick, the
bellmouth should be approximately .016". While a few thousands
of an inch either way will not materially affect the terminal's
performance, if the bellmouth is missing or if it is less than
one material thickness, there is a risk of cutting the wire
strands. The fewer strands that remain, the lower the
There is also a problem if the bellmouth is oversized (above),
because this reduces the total area that the crimp section
of the terminal has in contact with the wire. The less the
wire-to-terminal interface, the lower the wire pull out force.
If the crimp height is correct, then it is likely the problem is
caused by a worn hand crimper, which should be replaced.
Bent Lock Tangs.
Although bent lock tangs are not necessarily the result of a
poor crimping process, the connector can fail just the same.
Lock tangs (see above) may be bent either in or out too far,
which impacts the terminal's ability to completely lock
into the shelf in the housing that was designed for this
purpose. The tangs may be damaged by handling after
the terminals are crimped onto the wires, or if the wire
is soldered to the terminal pin (not recommended!)
While there are problems that may be
caused during the crimping process, there are just four simple
rules that will help ensure a successful connector application:
- Choose the right connector for your application requirements.
- Use the crimp tooling specified by the terminal manufacturer (there is
a different hand crimper for .156" and .100" terminal pins!)
- Properly inspect the crimp tooling to make sure it is not worn.
- Replace the hand crimping tool if worn, as the parts that displace metal
conductor and insulation wear.
Since most of the problems that are reported to connector
manufacturers relate to one of the above crimping problems,
Molex offers an easy-to-use guide to help you avoid problems or
recognize them quickly enough so that you make only good crimps.
To order this guide contact Molex Incorporated, 2222 Wellington
Court, Lisle, Illinois 60532, Attention: Good Crimp Drawings.
5. Should Connector Terminal Pins be Soldered?
Some field repair people feel that after a 'good crimp' is
performed on a new connector, the terminal pin should be soldered
to the attaching wire. Maybe they are used to dealing with
'bad crimps' or feel they need the additional piece of mind.
But is this the right thing to do?
The most common aspect of connector replacement in pinball is
the GI (General Illumination) connectors. These fail the most,
and require replacement most often.
The generally accepted crimp-on .156" terminal pin to use for GI circuits is the
style terminal pin (i.e. Molex part# 08-52-0113, Digikey part# WM2313-ND).
This terminal pin grabs the circuit board's header pin
on three sides instead of just one. Though the current handling capability
is not increased, the vibration resistance and durability of the pin
goes up dramatically.
If a trifurcon pin is properly crimped, there is NO need to solder
the connecting wire to the terminal pin. The only positive aspect of
soldering a properly crimped terminal pin is the "wire pull out force" goes up.
Current ratings do not go up with a soldered pin compared to a
properly crimped-only pin (that information is directly from
a Molex technical advisor who I talked with on the phone).
Now if there is a bad or improper crimp on a terminal pin,
solder can increase the performance of a crimp.
For example, a gas tight crimp is critical to long term performance.
If there are voids between the wire strands or between the
strands and the terminal because of a bad crimp, oxides can form
(oxides are of higher resistance than the clean metals).
Granted, in most
applications the performance increase is negligible versus an unsoldered
crimp, even a bad crimp. And the potential of doing "more harm than
good" is very high when soldering a terminal pin
(unless the user follows the terminal soldering method outlined below).
The risk of problems when soldering a terminal pin far out-weigh
the benefit in most cases. For example,
Adding solder to a terminal pin can get solder on the "locking
tangs", making it unflexible. This in turn can ruin the connector
housing, and make the pin nearly impossible to remove.
Soldering a terminal pin can also cause the terminal pin/wire insulation
joint to fail. Or in the worse case, it can melt the insulation back
beyond the pin, possibly causing a short.
Also, in extreme situations, Iain documents the melted plastic insulator
can wick down into the wiring, and cause the wire to become a
sort-of capacitor. This can cause some difficult diagnostic problems!
Another problem with soldering terminal pins (as documented by Bobukcat)
is having flux wick down and end up being left on the connector surface.
This can interfere with connectivity to the header pin.
Lastly, though unlikely unless extreme heat is used, the plating on the
terminal pins can be damaged by soldering.
Properly Soldering a Terminal Pin (if you must!)
With the potential problems of soldering a terminal pin known,
some users may still want that additional "insurance".
Or if a good crimp can not be performed (wrong tool or wire gauge?),
soldering may be necessary to overcome the bad crimp.
Molex reconizes that some user may not following
their crimping directions, and may solder a terminal pin anyway.
If this is the case, here is the ONLY terminal pin soldering
technique Molex (relucantly) recommends. This information came from
John Luthy, Molex's connector product division manager:
- Before crimping the terminal pin, tin the end of the bare
wire with some solder (best method is to dip the wire end
into a hot solder pot).
- Crimp the terminal properly (see the notes above!)
using a good quality hand crimper (Molex WHT-1921 part# 11-01-0015, Molex part#
63811-1000, or Amp 725).
- After the wire is properly crimped, using a temperature controlled
soldering station (750 degree maximum), heat the terminal pin momentarily,
right where the tinned wire is crimped in the terminal pin.
The tinned wire's solder should heat and reflow, spreading to the terminal pin.
Do NOT add any additional solder!
Talking to Molex representatives, they really discourage any terminal pin
soldering (a good crimp does not require soldering!)
But if it is done, the above steps are the technique to use.
6. Converting Looped IDC Terminal Pins to Crimped Pins.
Something often seen in many Williams, DataEast and Stern pinball games from the
late 1980s to the present are looped .156" Molex IDC terminal pins.
This is most often seen on power pins where there is a higher amount
of current coming into the circuit board, like on General Illumination
connectors and main AC power connectors. A single 18 guage wire will
come into a single IDC terminal pin, and then loop around to a second
IDC terminal pin. The two contacts are not used for redundancy (if one
pins burns for example the other is a backup), but are used to distribute
the current across multiple pins. In theory the current is spread across
two pins equally instead of just one pin, so each pin is handling half the current.
Looped IDC connectors on a early 1990s DataEast CPU board.
How to convert IDC looped terminal pins to crimped pins.
The looped wire is very easy to handle with an IDC (Insulation Displacement) style
connector. But unfortunately they are not so easy to deal when
using a crimped connector pin. Because IDC connectors are not a good long-term
system (as described extensively in this document above) and should not
be used when repairing connectors, we
must come up with a way to convert the looped IDC pins to looped crimped pins.
The problem is the crimped terminal pin is designed for a single 18 guage wire.
Yet we must somehow get two wires into the terminal pin (to create the loop),
and do a proper crimp on the double-wire pin.
The best way I have found to deal with this is to looped a wire in the
crimped terminal pin as seen in the picture below. Though this crimp is
hardly what Molex recommends for a proper crimp (as described above in this
document), I can't really come up with a better solution.
Picture by Ed of GPE.
There are two tricks to making this work.
The first trick is to solder the wires to the terminal pins as described
above. That is, lightly tin the two wires with solder
before crimping them. The key is to tin the wires very very lightly.
If too much solder is applied, the wire diameters will be too large and both wires
won't fit in the single terminal pin. Also do NOT twist the two wire together,
keep them separate and tin them separate.
Then after the wires are crimped, gently heat the
wires and pin (without adding any new solder) to melt the existing solder,
securing them all together to the crimped pin.
The second trick is to
use the insulation-grabbing part of the terminal pin as
an added area for the stranded wires. Because the insulation-grabbing
portion of a crimped terminal pin is larger, this additional area handles
the two wire together fairly well, without spilling-over the stranded
wires outside of the crimp. Though this is definately not how to do a
proper crimp, in this situation there really is no alternative. Note a bit of
practice is needed to get a feel for this "illegal" crimp.
An additional thing to remember is there's limited space inside the
plastic Molex connector housing for the two wires. So a clean and tight
crimp must be done. Be sure to inspect the crimp carefully for any
stray stranded wires that could short to adjacent pins after the
terminal pin is inserted into the plastic connector housing.
7. Removing Connector Terminal Pins.
Removing Molex terminal pins (either IDC or crimp-on varieties) is very
easy. Molex makes an official pin removal tool. But frankly, I would
not suggest buying it. There is an easier way.
An "official" Molex card edge pin extraction tool.|
It actually works Ok, and is made of spring steel.
Molex part number 11-03-0003. There is also a Molex removal
tool part number 11-03-0016 that is slightly different and
*much* better and easier to use.
The easiest way to remove a terminal pin is to use a small #1 flat head
screw driver. Look at the side of the connector, where the terminal pin's small lock barb
is seen through the side of the connector. Take the small screwdriver,
and push down on the lock barb, bending it down and out of the way.
Now just pull the wire connected to the terminal pin, and the pin should
just slide right out! It may take a couple practice tries to get the
right amount of bend on the barb (too little bend and the pin does not
unlock - too much bend and the pin gets distorted and doesn't pull out easily).
Also sometimes (especially on IDC connectors), the pin may need a small
needle nose pliers to pull it out of the plastic housing. Of course only
use this technique if the terminal pin is going to be replaced (which 99%
of the time that's why you're removing it!)
Removing the IDC pin with needle nose pliers after the "lock barb" was |
bent out of the way with the Molex tool (the blue circle shows where
shows where the lock barb was bent down). Frankly it's just easier to
use a small #1 flat head screwdriver instead to bend the lock barb.
Note this technique does *not* work for round Molex pins. In this case,
a specialized tool is definately needed to remove the round pins from
their plastic housing. There are two different round pin extractors.
The one for .093" pins is the most common in pinball (though the smaller
size is also used sometimes).
Left: Round Molex pin .093" extractor |
tool, and new crimp-on female Molex
Right: Radio Shacks' round .093" pin
extractor tool, part number 274-223.
Return to The Pinball Repair Guides.