SDS100: Cold Solder Joint

jonwienke

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As I've mentioned elsewhere, I sent my SDS100 in for the cold solder joint issue, and after about a month away from home, it came back working again. Until today. The A/C in my house is broken, and ambient has been 85F or so the last couple days, and so the SDS100 has been running warmer than usual as a result.

The symptoms were nearly identical to before, except instead of getting no RSSI reading while a transmission, I was sometimes getting -40dBm, which is unusually strong. Everything else was the same; super slow scanning, pulsing static on multiple channels, etc. Not relishing the thought of spending another month without the scanner, I opened it up to see what Uniden had done, in the hope that it might yield a clue to the problem. And I found something I'd missed previously:

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The third pin from the right seems to be the culprit. The solder connections on either side have touched up by hand, but the third one hasn't, and if you compare it to the machine soldered pins on the left, it has conspicuously less solder than all the others. After reworking that joint so it matches the others, the radio works properly again. Missing that dry joint is clearly a fail on Uniden's part.

The other thing I did was shimmed the SMA connector on rear circuit board so it isn't putting lateral stress on the connector. With the front circuit board screwed down lightly, there was a ~0.2mm gap between the inner SMA connector retainer and the case, and when tightening the outer SMA retainer, the rear board was pulled upward relative to the front board, which pulled sideways on the J401 connector.

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To solve the problem, I 3D printed a spacer that was 0.2mm thicker than the inner retainer, and installed it so that after tightening down the outer SMA retainer, the two halves of J401 are correctly aligned, and there is no lateral force on it.
 

kruser

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Great find Jon!

Now I know this so called CSJ can probably be fixed by those with the correct soldering tools, eyesight (and any needed external magnification aids!) plus steady hands. Even with my aging eyes, I could do as good or better of a job than I see in your picture.
I've always wondered if anyone with the CSJ issues attempted to inspect J401 and its mating connector. Now I know!

I'll need to look at the SMA spacing you found after tightening the board in mine next time I open it. That could very well be a manufacturing allowed tolerance but I agree and it should not exist. Especially if it puts stress on the J401 connector.

Thanks for posting the nice and clear pics along with your findings. That poor looking 3rd pin stuck out like a sore thumb before I even read your text.
I'd liked to have seen this radio's J401 before Uniden serviced it. That may have been interesting.
 

jonwienke

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Magnification is mandatory for this. The entire connector is only about 5/8" wide. Those pins are TINY. I looked at both halves of the connector without magnification before originally sending it to Uniden, and missed the dry pin. Seeing where Uniden did hand rework gave me the clue where to look further with magnification. And that's when I finally found the problem.

It just seems weird that when redoing a row of pins, you'd skip the one (or at least one of several) with issues.
 

jonwienke

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The connector is 11.9 x 3.4 x 8.1mm. Less than 1/2" wide.
 

Ubbe

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With the front circuit board screwed down lightly, there was a ~0.2mm gap between the inner SMA connector retainer and the case, and when tightening the outer SMA retainer, the rear board was pulled upward relative to the front board, which pulled sideways on the J401 connector.
That's probably the source to why the soldering breaks in that connector. And also explains why some people need repeat repairs of the same problem. That lateral mismatch needs to be fixed or the cold solder joint will keep reappearing.

/Ubbe
 

tumegpc

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jonwienke

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That's probably the source to why the soldering breaks in that connector. And also explains why some people need repeat repairs of the same problem. That lateral mismatch needs to be fixed or the cold solder joint will keep reappearing.
Agreed. I 3D printed a spacer that replaces the inner SMA retainer ring 0.2mm thicker than the ring, which fills in the gap shown in the second image. So when I tighten the outer SMA retainer ring, the case holds the connector in the proper lateral alignment.

Just in case, I purchased a new accessorie for the SDS100.
That actually looks useful. I'm currently using a lighted magnifier on my bench, and that isn't always enough to really see what's going on.

@jonwienke does this help on receiving the signal better?
Yes. When malfunctioning, you get pulsating static on every channel because the RF gain soesn't work properly. The noise reading would fluctuate between 0 and the low 10,000 range about 3x/second. Fixing that lets the receiver perform as intended.
 

kc5igh

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Wow! I'm glad you had the knowledge and experience to find out for yourself why your SDS100 failed again, Jon.

I hope Uniden reads your post and learns from it. My SDS100 got back from CSJ surgery at Uniden's repair shop a couple of weeks ago and has been functioning normally (fingers crossed). I'm guessing that someone out there touched up the connections by hand. If Uniden doesn't learn from your findings, you may be able to start a new service line to check/repair the connections and relieve the lateral stress on that connector.

In the meantime, I've switched carrying cases from the non-ventilated nylon case I purchased with the scanner to a ventilated, soft-leather carrying case from ScannerMaster. The soft leather case is a beauty, but I've decided to try out the ventilated, nylon case that ScannerMaster also offers for the SDS100 in hopes that it might be a little cooler.

Here's hoping my SDS100 doesn't suffer a relapse from one or both of the problems you found!

-Johnnie (KC5IGH)
 

dcr_inc

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Just in case, I purchased a new accessorie for the SDS100.

View attachment 89068
How do you like it?.. Is the image correct as in move hand left and you go to the left on the item?
 

hexagon_keyhole

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Is there a way to epoxy/reinforce the J401 connector so that it "stays in place?" I can't tell how the J401 connector is held in place; I hope it's not just those tiny connectors that is holding the weight of the J401.
 
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Ubbe

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How do you like it?.. Is the image correct as in move hand left and you go to the left on the item?
One thing to look out for are the delay it has from you move the solder tip under the lens and when it is presented on the display. Too much delay and you are bound to make mistakes when you solder and you will curse that cheap $50 microscope.

/Ubbe
 
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ArloG

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Pardon me but that is some of the crappiest rework I've ever seen.
Every pin on the connector should have been reflowed using liquid flux.
Were those traces on the right side of the connector blown?
 

KG4KHQ

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I really have been hoping for a replacement for my Home Patrol 2 in my vehicle. Right now I’m using it with a broken USB port on the side (powered by rechargeable AA’s) along with a 436 (with it’s crappy display) for DMR and NXDN. The SDS200 won’t fit and I really don’t want to take a chance with a SDS100 and the CSJ. I know others have not had any problems, but I just don’t want to buy something just to send it back for repair.
 

jonwienke

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I took it for a ride in my truck today, and it quit working again. It failed in the first 5 minutes, before the a/c had a chance to kick in. I'll post a video of what it's doing tomorrow.
 
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jonwienke

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Were those traces on the right side of the connector blown?
The traces and pins look ok, the soldering less so. Keep in mind the pins are spaced about 0.5mm center-to-center, and it's not easy to make a nice-looking joint that small. My rework is a little prettier, but not much.

Regardless, I'm not so much concerned with the aesthetics of the soldering as with the reliability and longevity of the connections. And at the moment, that seems to be a fail all around.
 
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