Hardware > Lynx EtherDongle

Potential power issue with EthD

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txag2008:
I've used my EthD the past two years for my shows and it's worked fine.  This week I've decided to pull it out of storage and play with some lights. When I hooked up the etherdongle to power and cat5 to my computer/hub I have no lights on either the Magjack or the green LED on the board.

I've been noticed the 3.3v regulator was very hot. I can unplug the wallwart and plug it back in and within 10 seconds the 3.3v regulator is too hot to touch. I measured voltage from the wallwart and got 10.2vdc (this is from a co-op and the label shows it to be 6vdc.)

What is the best way to test the 3.3v and 5v regulators? I have a good multimeter but not sure which pins to test. Also, is this high of voltage typical from the co-op wallwart and is the EthD tolerant of it?

tbone321:
No, it looks like the regulator in the wall wart has failed.  Before going any further, you need to replace that wall wart with one putting out the correct voltage.  After that, check the voltage on both the 3.3V and 5V regulator and see if they are both functioning.  The fact that the 3.3V regulator is getting that hot is not a good sign.  If the 5V shorted out, it may have caused serious damage to the board. 

n1ist:
Before you panic - linear wallwarts like this (just a transformer, rectifier, and filter cap; there is no regulator in there) show the approximate output voltage when fully loaded.  Unloaded, they will definitely read higher.  I just grabbed one from a Lynx wireless (rated 6V/300mA) and unloaded it measures 9V.  10.2V is probably correct for that one, as it is a 1A transformer.  As a matter of fact, RJ is counting on it being higher than 6V as the 7805 wants 7V or so minimum. 

Check the output voltages of the two regulators.  For the 7805, the center pin is ground and the right one (looking at the front of the package) should measure 5V.  For the 1117, the left pin is ground and the center pin or tab should be 3.3V. 

/mike

txag2008:
When plugging the wallwart in at first, the 1117 reads 3.7v but then begins to climb and got up to 4.8v before getting very hot and I unplugged the power.

 The 7805 read 6.2v at first but then began to climb and got up to 7.8v before I unplugged the power.





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txag2008:
Hate to be desperate, but any advice?

Is this indicative of a a failed wall wart?  Failed voltage regulators?

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