Author Topic: 100ohm resistor is very hot  (Read 4017 times)

Offline salongaopm

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100ohm resistor is very hot
« on: September 30, 2013, »
the 100ohm resistor in ss Hub is very hot that i think it made a burnt mark on the board. is this something to be expected? please see attached picture.


Offline tbone321

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Re: 100ohm resistor is very hot
« Reply #1 on: September 30, 2013, »
The 100 ohm resistor is not the correct value.  It is supposed to be a 150 ohm resistor.  Yes it does get hot but the 100 ohm actually gets hot enough to unsolder itself from the board.  The purpose of this resistor is to put a load on the PS so that the regulators work properly.  100 ohms draws way too much current.  Don't continue to use the hub this way or you may end up damaging the board.  You can get the correct resistor from Radio Shack.
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Offline JoeFromOzarks

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Re: 100ohm resistor is very hot
« Reply #2 on: September 30, 2013, »
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100 ohm 3W

The solder joints look a little "cold" but may be from the resistor warming.  Desolder and reapply.

On our boards I raised the 100 ohm about 3/8" 1/2" off the PCB.

:) joe
« Last Edit: September 30, 2013, by JoeFromOzarks »
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Offline tbone321

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Re: 100ohm resistor is very hot
« Reply #3 on: September 30, 2013, »
The WIKI shows it as a 150 ohm resistor and that is what mine have.  now that I think about it, it may have been a 50 ohm resistor that unsoldered itself from a few boards.  I still believe that 100 ohm is still too low and draws way more current and gets much hotter than it needs to.
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Offline rrowan

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Re: 100ohm resistor is very hot
« Reply #4 on: September 30, 2013, »
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The WIKI shows it as a 150 ohm resistor and that is what mine have.  now that I think about it, it may have been a 50 ohm resistor that unsoldered itself from a few boards.  I still believe that 100 ohm is still too low and draws way more current and gets much hotter than it needs to.

I know the first coop of the etherdongle had a 49k resistor that unsolder itself.

Rick R.
Light Animation Hobby - Having fun and Learning at the same time. (21st member of DLA)
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Warning SOME assembly required

Offline JoeFromOzarks

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Re: 100ohm resistor is very hot
« Reply #5 on: September 30, 2013, »
Are we talking about the Smart Hub?  The WIKI shows 100 ohm (as does Mouser BOM, the link above) and the hubs I have here have 100 ohms.  If they are supposed to be 150 ohm I missed the parade.   If we're not talking about the Smart Hub then I'm a Pepsi short of having a complete morning. 

:) joe

(Was "were" not "we're" proving I was a Pepsi short!)  :)
« Last Edit: September 30, 2013, by JoeFromOzarks »
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Offline chrisatpsu

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Re: 100ohm resistor is very hot
« Reply #6 on: September 30, 2013, »
check the resistor with your multi meter to see it it's still 100 ohms.

it might be off spec, or something might have happened to it.
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Offline tbone321

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Re: 100ohm resistor is very hot
« Reply #7 on: September 30, 2013, »
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Are we talking about the Smart Hub?  The WIKI shows 100 ohm (as does Mouser BOM, the link above) and the hubs I have here have 100 ohms.  If they are supposed to be 150 ohm I missed the parade.   If were not talking about the Smart Hub then I'm a Pepsi short of having a complete morning. 

:) joe

LOL, you are correct, mine does have the 100 ohm resistor installed.  I seem to have way to many things going on to keep things straight.  Like Rick said, it was the 50 ohm (47 ohm) resistor that decided to remove itself from the boards that it was installed on.  The correct resistor does get hot but I don't remember mine getting hot enough to scorch the board.  As Chris suggested, I would measure the actual resistance and make sure that the resistor is in spec.
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Offline zwiller

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Re: 100ohm resistor is very hot
« Reply #8 on: September 30, 2013, »
No comment on the resistor value but mine also gets hot like "the waitress warned me the plates were hot but I didn't believe here so I touched it and now I have a 1st degree burn" hot...  But, no burns on board or issues with desoldering... 
Sam, who is happy he flashed his etherdongle with newest firmware!

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Offline salongaopm

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Re: 100ohm resistor is very hot
« Reply #9 on: September 30, 2013, »
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check the resistor with your multi meter to see it it's still 100 ohms.

it might be off spec, or something might have happened to it.

 i will check it afterwork tomorrow morning.
you are probably right that it is off spec base on this thread You are not allowed to view links. Register or Login 


Offline RJ

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Re: 100ohm resistor is very hot
« Reply #10 on: October 01, 2013, »
100 ohm is correct. the wrong ones sent out where 15 ohm. they would desolder themselves fairly quick.

they will get fairly hot so you do not want to touch them. They are 100 ohm because some Power Supplies do not regulate very well without a decent load and so if your lights are all turned off you need a good load on the power supply.

RJ
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Offline pk

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Re: 100ohm resistor is very hot
« Reply #11 on: October 01, 2013, »
The 100 ohm resistor is rated at 3 watts and is dissipating 1.44 watts. 

Offline salongaopm

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Re: 100ohm resistor is very hot
« Reply #12 on: October 01, 2013, »
i am getting a reading of 18 :(

Offline tbone321

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Re: 100ohm resistor is very hot
« Reply #13 on: October 01, 2013, »
You need to remove one of the legs from the board to get an accurate reading.  Measuring the resistance with the fuse installed then also measures the resistance of the rest of the circuits that the resistor in in parallel with.  If it is really 18 ohms then you would need to remove and replace it anyway so you can start by removing one leg and then measure it again.  If it is still 18 ohms then it really needs to be replaced but at 18 ohms, I think that it would remove itself.
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Offline salongaopm

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Re: 100ohm resistor is very hot
« Reply #14 on: October 01, 2013, »
i removed it from the board and it is giving me a reading of 17-18