Lynx Build

[IndianaChristmas]

I have built several Expresses over the last year and I finally had an issue I haven't been able to fix.
I turned on my last one and the middle LED module doesn't light up.  The rest of the board tests out OK.  (I haven't hooked lights to it but the test sequence runs to completion.)
I have looked at the solder joints, reseated the chips etc. Swapped out LED modules.
I can post pics but I was hoping someone might be able to tell me the most likely issue that would cause this.

Thanks,
Eric

[inzeos]

I believe their was a similar issue reported recently with the same problem.  I believe the end result was to replace the small cap; however, don't quote me on that!

[dlhoppe]

Yeah, there's been some discussion about that issue. I believe it's related to the 2700pf cap that sits next to the 3rd digit. Either there's been a run of bad ones, or they're a little more sensitive to heat during soldering than other components. Look closely at the solder joints on that one, but be careful not to heat it any more than necessary. If it's bad or was damaged by heat, there's nothing you can do but replace it.

[RJ]

Actually we have found that if it is set to deep in the board it might be solder but not making connections so first heat it and raise a up a little. But the 2700uf tiny capacitor is the only thing that will cause this or soldering on it or the display chip pins hooked to it.

RJ

[IndianaChristmas]

I suspect since it is just the LED module that is affected the rest of the board will work OK.  Am I correct?
I have tried to remove the cap but haven't been able to.  I'm willing to leave it alone.  I think I can set channels without the middle module working.
Eric

[lineman]

I suspect since it is just the LED module that is affected the rest of the board will work OK.  Am I correct?
I have tried to remove the cap but haven't been able to.  I'm willing to leave it alone.  I think I can set channels without the middle module working.
Eric

Radio shack has a great desoldering tool for $11.00 it works great, I have tried solder suckers and wick and have had no luck but this desoldering tool is the bomb let it hest up and release the ball and the solder is gone the part will practically fall out
You are not allowed to view links. Register or Login

[combustionmark]

The LE will work just fine with this bad cap, Just a Little difficult to set address.

My experience with different desoldering tools.
#1 Spring loaded solder suckers. Just seams to remove a bit more solder.

#2 Soldering iron with the red ball sucker, This is the easyest to use, but it gets too hot so be carefull with it.

#3 Red ball sucker, Plugs up easily

#4 Solder wick, works best but takes a lot of practice. This is what I use most of the time.

What ever you use, practice on an old circuit board first, Something out of an old clock radio, or cassette player , is a good starting point. Computer equipment is quite a bit more difficult.

PRACTICE! PRACTICE! PRACTICE! take a break. PRACTICE some more.

You built it, you can fix it.

Good luck

[IndianaChristmas]

I have built a total of 8 expresses.  The last two have issues with the middle LED module not lighting up. I just finished another express after I posted the initial issue.
I made sure this time and followed RJ's advice and made sure I didn't seat the 2700uf cap too low.  Still the same issue.
I don't solder with the LED modules in place so I know I'm not hurting them.
Could it be the caps aren't good?

Eric

[dlhoppe]

I bought this tester for capacitors, transistors, inductance and resistance. For less than $20 including shipping, this is well worth the money. It feels pretty substantial (although case is plastic) and has a nice backlit LCD. I've tested known good components and it seems pretty darn accurate. You might want to consider adding one to your "arsenal". Might come in handy for issues like this.

You are not allowed to view links. Register or Login


Cheers,
Dave

[RJ]

I have built a total of 8 expresses.  The last two have issues with the middle LED module not lighting up. I just finished another express after I posted the initial issue.
I made sure this time and followed RJ's advice and made sure I didn't seat the 2700uf cap too low.  Still the same issue.
I don't solder with the LED modules in place so I know I'm not hurting them.
Could it be the caps aren't good?

Eric

did all 8 come from the same coop? which coop?

If not did the two with issues for sure come from the same coop? which coop?

RJ

[IndianaChristmas]

My first 5 builds came from a coop last year; no isuses.
I have built 4 from the first coop of this year, the first 2 builds had no issues, the last 2 I had the problems.
Eric

[TexasStingray]

I built 6 from this years first coop. No problems, made sure I did not keep the heat on any component, using just enough solder to make a sure join not to much and not to hot.

[RJ]

Seems odd to have this issue when we have not before. If anyone needs a cap to replace one let me know I will order some spares on my next order to mouser.

RJ