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Motorola Control Cable Connector Virus By Robert W. Meister WA1MIK

Ever wonder which came first: the chicken or the egg? Well, I've got a similar situation with some Motorola MaraTrac radios. The radio chassis (drawer) employs a unique 19-pin connector that's used by Motrac, Motran, Mitrek, and MaraTrac radios, and probably a few others I'm not even familiar with. Three large pins in the middle handle power, while two rows of 8 smaller pins handle other signals. A large thumbscrew is used to insert, retain, and remove the cable end into the radio's connector. Here are photos of the cable end and the front of a MaraTrac, both unaffected:

The Players:

Here's the list of participants. Remember, you can't tell the players without a scorecard! And, yes, Who is on first!

• Original MaraTrac radio (110w, 42-50 MHz), now known as Radio-1.
• Original cable (with A7 control head, speaker, mike), now known as Cable-1.
• Second MaraTrac radio (110w, 42-50 MHz), now known as Radio-2.
• Third MaraTrac radio (110w, 42-50 MHz), now known as Radio-3.
• Repair cable (with A7 control head, speaker, mike), now known as Cable-2.

Radio-1 and Cable-1 are my operational setup that I use all the time in my house. The output power is set for 60 watts and the control head and accessories are mounted on a wood board that sits next to my couch (yes, I'm a couch potato). I bought this radio in 2008 and it's been working fine, however in March 2010 it developed an intermittent receive issue.

Cable-2 has short DC power leads and is used only for repairing, testing, and aligning MaraTrac radios on the bench.

Radio-2 and Radio-3 were bought as a pair in March 2010 so I'd have a spare to swap with Radio-1 if I was unable to fix it quickly. I put each of these on the bench and did a quick operational and alignment check using Cable-2. Radio-2 worked fine but Radio-3 had a very deaf receiver that was missing about 40dB of sensitivity. I later replaced the first RF amplifier transistor (open in all directions) and the protection diode across the receiver antenna input (2 ohms in both directions) on the RF board and that brought the receiver back to life.

Now that I had two good, working radios, I pulled Radio-1 out of service and put it up on the bench. I checked the VCO adjustments and touched up the alignment, then put that radio back in service. I also converted Radio-2 and Radio-3 to six-meter operation and cloned the Radio-1 code plug into them. I now had three working six-meter MaraTracs.

One morning I was chatting with someone with Radio-1 and it seemed to be working fine. Later in the afternoon I was talking to Dave N1OFJ with the same radio and got a report of very low transmit audio. I verified this by listening on the radio's output frequency with another receiver and the audio was barely audible. The quickest way to deal with this was to just swap radios, so I removed Radio-1, grabbed Radio-2, put it where Radio-1 was, and plugged Cable-1 into it. I then continued the conversation.

Viral Symptoms:

After removing the control cable from Radio-1, I just happened to notice that one of the small pins (#9) on the radio's connector was slightly bent outward. I disconnected Radio-2 and saw that it had the same pin bent. I gazed into the connector at the end of Cable-1 and noticed that the female contact had been deformed and pushed inward such that a pin would not fit into the middle of the connector but would be pushed off to one side, hence the bent pin #9. Here's a photo of the connector on Cable-1 showing the deformed contact. Compare that to the ones next to it:

I checked Cable-2 and found that it too had the same female contact pin #9 deformed in the same way. I checked Radio-3 and it also had a bent pin #9. At this point, all three radios had bent pin #9 and both control cables had a deformed contact #9.

I don't know whether the bent pin #9 caused the female contact deformity, or if the contact deformity bent the pin (in other words, "Which came first: the chicken or the egg?"). I do know that any radio I attached to either Cable-1 or Cable-2 would end up with a bent pin #9 and straightening the pin would not fix the problem since it would just bend again when it was connected to either control cable. Here's a photo of the connector on Radio-2 showing the bent pin (click on the image for a larger view):

Somehow I ended up with three radios with bent pins, and two control cables with deformed pins, and it seemed to spread to, and affect, every radio and control cable in my house.

I had loaned Dave N1OFJ my Cable-2 several months ago so he could work on his two radios. He checked both of his installations: no bent pins on either the radios or the control cables.

Fixing the Damage:

I removed the damaged female contact. Here's what it looks like from the back side. Notice that one of the two tangs has been pushed in.

I tried to unbend the female contact using some sharp pointed implements, but the metal was bent over in such a way that it would not move and nothing would fit into the tiny opening in the middle. I pulled the Cable-2 connector apart and removed the #9 contact. I was able to straighten the bent piece but then it just snapped off. Here's what a broken one looks like, also from the back side:

I reinstalled it and determined that the remaining metal part would still make contact with the radio's connector pin. In the meantime I began searching for replacement female contacts. A couple of days ago, Dave N1OFJ gave me an old Mitrek control cable and I removed two small female contact pins from that. I used one to replace the bad contact in Cable-2 and the other will be used to fix Cable-1 later today. Here's a photo of one of these female contacts:

I've since straightened the bent pin #9 on Radio-3. Radio-2 and Cable-1 are still in service and still have the problem. I won't swap radios to use Cable-1 until I've replaced the female contact in Cable-1, at which time I'll also straighten pin #9 on Radio-1 and Radio-2.

Conclusion:

So which came first: the bent pin or the deformed contact? I suspect that one of the new units (Radio-2 or Radio-3) had a bent pin #9, and when I connected one to Cable-2, that caused the deformity of the female contact. Since I attached both radios several times, both Radio-2 and Radio-3 ended up with bent pins. When I removed Radio-1 and put it on the bench to tweak the alignment, Cable-2 caused pin #9 to bend on that radio as well. When I put Radio-1 back into service, the bent pin #9 caused the female contact in Cable-1 to become deformed. Between the radios and cables, any combination would result in a bent pin. The only way to completely fix the problem is to replace both female contacts and straighten out all bent pins at the same time, and not swap radios around until that has been accomplished.

Mike WA6ILQ proofread this article and commented that the metallurgy of the pins is such that they can be bent and straightened maybe ONCE, and the next time they will snap off. Apparently as the pin bends it gets very brittle at the bend point. The sockets in the female connector are a softer spring metal and are individually replaceable; the pins in the male connector are molded into the plastic and must be replaced as an entire assembly.

He also commented that many years ago he had a bent pin #1 (microphone audio) on a newly acquired low band GGT (pre-Motrac) that broke off the instant he tried to straighten it. He ended up using the F4 pin as the MIC Audio pin until he could acquire a replacement connector and change the connector in the front of the radio.

(As far as the perennial question goes, I think the rooster came first.)

Removing Contact Pins (yes, there is a secret):

I opened the connector housing using a Torx T-10 driver and removed one half of the cover. I then removed the cable clamp inside using a 1/4-inch (#8) nut driver and removed the other half of the cover. This leaves just the connector body and the big thumbscrew. I pulled back the rubber sleeving over pin #9 and unsoldered the wire from the damaged socket pin. This is what things look like at this point; click on the image for a larger view:

You might notice a small dimple on each socket pin right next to the black plastic connector body. These keep the pins from falling out. Remove any solder from the concave side of this dimple, then use a pair of stout needle-nose pliers and squeeze the dimple until the whole solder lug is straight. You may have to do this multiple times. The pin should then just fall out, although a damaged one may have to be forced out.

Replacement is even simpler. Insert the new pin, bend it just a bit behind the plastic connector body, or add a big glob of solder to the area where the dimple was, attach the wire, and reassemble the connector. Don't use so much solder that it flows down into the pin contact area; you'll never clean it out.

Conclusion:

I called Motorola Parts ID and after a lot of research they told me the part number for the small female contacts that fit into the plastic connector body are p/n 3984257L01 and they cost $1.79 for a pack of two. I will buy one package on my next parts order.

UPDATE 08-May-10: The above part number is NOT for the contacts that fit the big connector that plugs into the radio. They seem to be for something else, possibly the connectors up at the control head. Either the Parts ID guy looked at the wrong end, mis-read the part number, or Motorola put the wrong parts in the bag.

UPDATE 10-May-10: Motorola Parts ID was unable to give me a part number for the small female contacts that fit the radio-end connector. They had nothing that broke it down to the individual part level. They did give me the part number for the entire 19-pin female connector, which supposedly includes all of the pins: p/n 0980169C01. For only $10.08US, you get the molded plastic, 16 small female contacts, and three large female contacts. What a deal!

UPDATE 17-May-10: I got the above connector: exactly as described and it IS the right one. Naturally, Motorola is not producing these any more, so when they've exhausted their current stock, that's it. If you own any of the radios that use this control cable connector, it might be wise to buy one while they're still available. Here's what it looks like.

UPDATE 15-May-12: Motorola no longer has a price listed for the above part (connector and pins), so it seems their current stock has been exhausted.

Contact Information:

The author can be contacted at: his-callsign [ at ] comcast [ dot ] net.

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This page originally posted on Wednesday 07-Apr-2010.

Photographs, article text, and hand-coded HTML © Copyright 2010 by Robert W. Meister WA1MIK. All photographs were taken by the author.

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.