Author Topic: FIXED!! No lights on MagJack, Ethernet chip hot  (Read 2444 times)

Offline akonkman

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When I power up the EtherDongle, the green LED comes on, and sometimes the yellowish-orange light on the MagJack also comes on, faintly.  When I plug in a Cat5 cable that runs back to a switch, no activity lights come on on the EtherDongle or my switch.  I also notice that the Ethernet chip on the board gets pretty hot within short order... not sure if this is normal or not.

I've checked, and I don't see any solder bridges around either the ethernet chip or the PIC32, except for a bridge on pins 35-36 on the ethernet chip, which I understand is normal.

I don't see any other solder bridges anywhere else on the board either.  I'm at a loss as to what to try next.

Thanks,

Andy
« Last Edit: April 13, 2012, by akonkman »

Offline bisquit476

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Re: No lights on MagJack, Ethernet chip hot
« Reply #1 on: April 12, 2012, »
Try posting some clear hi-res pictures and we'll take a look.

Offline akonkman

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Re: No lights on MagJack, Ethernet chip hot
« Reply #2 on: April 12, 2012, »
Here are some pictures.  I tried attaching them to this post, but that didn't seem to be working.  Anyway, you should be able to get to them here:  You are not allowed to view links. Register or Login

I have to admit this isn't my best soldering job, but from what I can tell, there are no bridges or cold joints.  But I appreciate some other sets of eyes looking at it :)

Thanks.

Offline RJ

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Re: No lights on MagJack, Ethernet chip hot
« Reply #3 on: April 12, 2012, »
Hold your pcb up to a very bright light and get it close. Then look at the chips close with the light coming throught the pcb. Can you see anything wrong? 

This looks like a second coop pcb so it is likely it is good but check it for anything. One user had a simuliar problem and had a cut of of a part he trimed that got between the pins of one of the chips.

RJ
Innovation beats imitation - and it's more satisfying

Offline akonkman

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Re: No lights on MagJack, Ethernet chip hot
« Reply #4 on: April 12, 2012, »
Nice idea, RJ.  I held it up to a light and took some pictures too.  You can see them at the link above.  I think it looks good, but perhaps there's a flake of something in there.  I'll try to clean between each one with a little exacto knife or something and see what happens.

Is it normal for the ethernet chip to get hot enough where it's pretty much unbearable to touch it?

Offline RJ

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Re: No lights on MagJack, Ethernet chip hot
« Reply #5 on: April 12, 2012, »
No the chip does warm up good but not that hot. Becareful with a knife to not damage pins or ruin the traces. Better to put a lot of flux down and using a soldering iron that is spotlessly clean (no solder at all on it) touch it the pins that you think are bridged and wait till the flux finishes flashing away and is all gone. Shoudl be about 2 - 3 seconds. Then remove it by sliding away form the chip at a 90 deg stright out. It will tend to take any excess solder with it on the tip of the iron and if there is a bridge the flux normally will make it flow and move to the pins breaking the connection.

Do not touch the chip pins with any solder on your iron or you will have a mess.

RJ
Innovation beats imitation - and it's more satisfying

Offline akonkman

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Re: No lights on MagJack, Ethernet chip hot
« Reply #6 on: April 12, 2012, »
I'm stumped.  I just don't see any bridges between the pins. Are there some tests I can do with a multimeter to check if certain things are working correctly?  I tested the oscillators, and they seem to read OK (3.3V on pins 4-8 and 1.6V on 4-5).  I'm afraid to leave the thing plugged in for too long at a time, since that ethernet chip seems to get so hot and I don't want to burn something up. 

One other interesting tidbit.  Just for fun, I tried erasing the Pic32 chip.  When I supplied power, that green LED still lit up.   From what I understand, that thing shouldn't light up unless the Pic32 chip is flashed with some firmware.  And sometimes (not always) the yellow LED on the MagJack also lights up.

Offline akonkman

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Re: No lights on MagJack, Ethernet chip hot
« Reply #7 on: April 12, 2012, »
One more thing I just noticed... every once in a while, when I supply power to the board, the green LED lights for just a split second, and then remains off. 

Offline akonkman

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Re: No lights on MagJack, Ethernet chip hot
« Reply #8 on: April 13, 2012, »
SUCCESS!!   ;D  Or at least, I've got lights blinking on the MagJack now!!  This is what I did:  With a sharp clean soldering tip, a magnifying glass, and steady hands, I touched each and every pin on both chips in an attempt to reflow each one in case there was a cold joint somewhere.  Then, I took some desoldering braid, laid it across each side in turn, and placed my soldering tip along it, trying to soak up any extra solder.  I didn't have any flux around at the time, so I didn't use that.  I actually did this procedure twice.  Once last night, with no success, and then again this morning.  Second time's a charm!  That ethernet chip feels a bit cooler now as well, since I can place my finger on it and leave it there without feeling discomfort.

As soon as I applied power, I knew something was different, since that green LED glowed brighter than it ever did before.  Then, as soon as I plugged it in to my switch, voila!  The green light on the MagJack is solid on, and the yellow one is blinking with activity.

Now, on to testing it through Vixen on a Smart String hub.

Thank you RJ for having faith that this was simply a bridged connection somewhere, even though I couldn't see it.


Offline pk

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Re: FIXED!! No lights on MagJack, Ethernet chip hot
« Reply #9 on: April 13, 2012, »
Glad it is working for you now.