"Molexia" Molex Connector Solder Crystalization/Cracks
Posted: Mon Oct 12, 2015 7:32 am
Anyone owning or servicing MCI JH-series equipment are familiar with Molex connector problems.
One of the greatest source of transport instabilities once all the machine's IC sockets are replaced are intermittent Molex connections.
Oxidation of the tin-platted round contact pin and leaf spring mating connector are usually blamed.
Rub the pin with a dry Q-tip or run a pipe cleaner through the female connector and they'll be black in no time flat.
But there is a far worse problem beneath the surface: Ring cracks around the pins where it solders to the PC board.
Those will make the machine highly intermittent - particularly on the Analog Torque board.
Until the transport motherboard is completely re-soldered and cleaned (removing the flux off the pins) it will produce nothing but trouble.
I made a career out of resoldering motherboards and replacing sockets.
We have to remember that many of MCI's PC boards had components stored in a coastal area and de-fluxed in household dishwashers.
Molex solder ring cracks are not limited to MCI gear.
I would always look for ring cracks on these pins no matter who made the gear.
Power connections are the worst.
Many a blackened Molex power connector can be traced back to the solder joint failing and not the contact itself.
Square Molex pins can also do this though I don't see it as often. Round were the worst.
Always look for microscopic crystallized cracks and re-solder those Molex pins..
One of the first things I did when I got the Texars on the bench was to pull out the motherboard and re-solder those pins.
In 1990 I didn't have a digital camera. Today I do.
This, ladies and gentleman is a textbook case of "Molexia" soldered Molex ring cracks.
Solder connections to round Molex pins develop crystallized microscopic ring cracks around the pin over time that must be resoldered.
Virtually every pin in all three Texars looked suspicious. The above are some of the worst on that row.
Every single Molex pin was resoldered. New flux has to be applied.
One of the greatest source of transport instabilities once all the machine's IC sockets are replaced are intermittent Molex connections.
Oxidation of the tin-platted round contact pin and leaf spring mating connector are usually blamed.
Rub the pin with a dry Q-tip or run a pipe cleaner through the female connector and they'll be black in no time flat.
But there is a far worse problem beneath the surface: Ring cracks around the pins where it solders to the PC board.
Those will make the machine highly intermittent - particularly on the Analog Torque board.
Until the transport motherboard is completely re-soldered and cleaned (removing the flux off the pins) it will produce nothing but trouble.
I made a career out of resoldering motherboards and replacing sockets.
We have to remember that many of MCI's PC boards had components stored in a coastal area and de-fluxed in household dishwashers.
Molex solder ring cracks are not limited to MCI gear.
I would always look for ring cracks on these pins no matter who made the gear.
Power connections are the worst.
Many a blackened Molex power connector can be traced back to the solder joint failing and not the contact itself.
Square Molex pins can also do this though I don't see it as often. Round were the worst.
Always look for microscopic crystallized cracks and re-solder those Molex pins..
One of the first things I did when I got the Texars on the bench was to pull out the motherboard and re-solder those pins.
In 1990 I didn't have a digital camera. Today I do.
This, ladies and gentleman is a textbook case of "Molexia" soldered Molex ring cracks.
Solder connections to round Molex pins develop crystallized microscopic ring cracks around the pin over time that must be resoldered.
Virtually every pin in all three Texars looked suspicious. The above are some of the worst on that row.
Every single Molex pin was resoldered. New flux has to be applied.