"Molexia" Molex Connector Solder Crystalization/Cracks

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mediatechnology
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"Molexia" Molex Connector Solder Crystalization/Cracks

Post by mediatechnology » 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.

Image
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.
https://ka-electronics.com

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Re: "Molexia" Molex Connector Solder Crystalization/Cracks

Post by emrr » Mon Oct 12, 2015 9:20 am

Veer:

I have a Mackie that requires cleaning of all the ribbon cable connections every few years. You'll lose channels, or busses, or solo capability, etc.

I pulled apart a Dolby 740 and cleaned it's connections, it uses stacked PCB's that 'impale' in a sandwich with gold square pin connector forks soldered to the bottom board only. This made a difference in sound.

Some Quad Eight preamps I racked up about 10 years ago used the JLM go between boards, and I made use of their Pheonix connectors rather than soldering. Several of those racks came back in the last 2 years for service, and all had intermittent contact in those connectors, in several cases the screw pressure had loosened and the wire was barely captive. When they left here originally they were torqued as tight as reasonable without threatening connector (plastic) integrity.

Plastic 1/4" insert jacks in Ampeg and Marshal amps. Single biggest source of failure. Anyone carrying an amp with this 'feature' should always keep a short 1/4" jumper to make a hard external loop from 'out' to 'in' when failure strikes, it would save many a gig.

I had a pair of Alesis Monitor One speakers, which were known for the 'vibratory severing' aspects of their crossovers, which were soldered directly to the binding posts on one end of a horizontal PCB with no other support or shock mounting. Kinda like a weighted diving board. Caps and resistors would eventually sever their leads.

Alesis also had ribbon cable connector oxidation problems with their BRC controller unit.

None of these are this problem. So even without the cracks (thanks for the post and pic), I distrust non-soldered connections in the long term, and like this there are plenty of soldered connections that take varying stresses down to expansion/contraction/dissimilar metals which will work their way funky. Lots of musical instrument (heavy hands on) connections (audio/midi/power/footswitch) get fatigued and fail in manners ranging from obvious to not so obvious like that pic.
Best,

Doug Williams
Electromagnetic Radiation Recorders

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JR.
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Re: "Molexia" Molex Connector Solder Crystalization/Cracks

Post by JR. » Mon Oct 12, 2015 9:22 am

I am currently experiencing similar poor solder joint quality while using some decades old solid bare hook up wire. I guess after 40 years the wire surface has oxidized. :oops: I have already removed and thrown away the outer layers, but wire still seems lass than pristine.

Does flux help with your molexia or just use the flux in new solder?

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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mediatechnology
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Re: "Molexia" Molex Connector Solder Crystalization/Cracks

Post by mediatechnology » Mon Oct 12, 2015 10:39 am

I usually use flux in new solder. They seem to take new solder well.
For really stubborn discolored ones like overheated power connectors I will use added flux.

The gold square pin version of those connectors were pretty good.
The square pin versions are OK and usually much shinier tin.

There's something about the chemistry of the tin-plated round wire they used that must cause the crystallization.
I don't think its mechanical.

I expect to hear from Brain Roth soon on this one.
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

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Re: "Molexia" Molex Connector Solder Crystalization/Cracks

Post by brianroth » Wed Oct 14, 2015 7:20 pm

I don't know how many dozen MCI recorders (and oddly, lesser quantity of desks) that I've resoldered Molex connectors.

It was my understanding that MCI's problem was due to improper wave soldering. By the time that Sony bought them out, they seemed to had the problems mostly sorted out. IOW, I've seen far less problems with the Sony badged machines.

Bri
Professional audio and video systems design/installation/maintenance.
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