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My Uno Board worked great for one month then yesterday I must have gotten careless and burned something up while testing a stepper motor. Now when I connect it to my usb cable it lights up and connects to my PC then right under the usb connection it gets really hot and the lights go out and my PC no longer sees the board.

My question is how do I diagnose the burned out part and is it worth replacing the parts?  I am worried about over heating board if I desolder the voltage regulator or any other part that may have blown.
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Correction the part that gets the hottest on the board is the SPK16.000G
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That is just the quartz. I doubt it is the origin of the heat. Probably some IC nearby is fried.

It would be interesting to know if the board is initially detected by your PC and then after a few seconds craps out and heat up. If that is the case the USB chip might still be OK and some other part (maybe one of the voltage regulators) has had it.

If you have a small pipette and some sort of alcohol you can place small droplets on the ICs and see which one evaporates first. That is a cheap alternative to using a contact thermometer.
« Last Edit: June 09, 2012, 01:34:20 am by madworm » Logged

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It would be interesting to know if the board is initially detected by your PC and then after a few seconds craps out and heat up. If that is the case the USB chip might still be OK and some other part (maybe one of the voltage regulators) has had it.

Yes that is exactly what is happening! Could this indicate a regulator?

Unfortunately I don't have a pipette but if it is a voltage regulator, they are awfully small to unsolder and replace especially someone with limited soldering skills. I wonder if the parts are even available?
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Well, you can look for substitutes. It may get a bit tedious though. The bigger regulator (SOT-223) would be the easiest to replace. Best if you could find someone to do it ;-)
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Thanks for your advice! I think I will try and find someone to help me with replacing the parts.

Meanwhile do you know how I would test the regulators? I would asume that on the three pins, the middle is ground and the other two would be in and out? Should I get continuity between them if it is bad or am I all wrong with my assumption?
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Please don't assume, that leads to further destruction. The pin assignments on these components are not always the same. You'll have to use the datasheet to identify which is which.
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Should I get continuity between them if it is bad or am I all wrong with my assumption?
Continuity test of a component doesn't always tell you much.  Continuity test of parts that are in circuit are worthless.
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I think me best solution is to order this kit.  http://www.jameco.com/Jameco/workshop/JamecoBuilds/arduinocircuit.html?CID=HPWARDBREAD This way I can learn more about each component and if I burn something up it will be easy to replace. Thanks guys for your comments!
« Last Edit: June 11, 2012, 08:52:29 am by infoseek » Logged

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Did you use your 'Digital Wattmeter' (index finger) to find if anything else got hot?. Usually a failure of that type isn't the regulator as all of them have an over current shutdown (short circuit proof) but most likely to be a shorted cap... One of those silver things behind the PSU connector. You Might use a DMM to measure the 5V source with everything disconnected completely, connect a DMM to ground  (The outside bottom point on the Ext. PSU connector) and measure the 5V source resistance, on my Uno R3 facing so the connectors (USB & Power) are on my left, the one on the right is the 5V source and measures ~18 - 20 K and rises in value as it charges (Normal for an electrolytic). If the measurement on the right one (5V source) is low or doesn't rise in value then there is an issue/shorted part on the 5V source. The Processor is socketed and you might pull it just to see if the reading changes drastically, if so then you bricked the 'Proc' if not it is likely that the capacitor you are measuring from is bad. I measured a China R2 Clone and a 'Genuine" R3, both were the same and Both were running sketches when I disconnected them and made the measurements. It Is "In My NOT SO Humble OPINION" a very BAD IDEA to connect a servo Directly to the UNO or any other Arduino board's 5V source... Period, a Very BAD Idea. Always use an External Source to power Servo's when testing... saves a lot of potential greif IMNSHO

Doc
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Thanks Doc! My meter is at home but will test as you say tonight.

Meanwhile I did test with my finger and found the hottest component on the board as shown in my attached pic.



* ArduinoUno_R3_Front_450px.jpg (81.83 KB, 450x311 - viewed 26 times.)
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If you don't find someone with proper gear and experience, this one will be tricky to replace.

And with part and shipping costs you may end up pretty close to what 1/2 of the full board costs. And if you don't get all the bad ones in the first go you'll need another iteration. Might not be worth the trouble. Best to use the modular approach you were talking about.
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• Your AVR needs a brain surgery? Use the online FUSE calculator.
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• Microsoft is not the answer. It is the question, and the answer is NO!

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By the picture an R3 Uno and the part you identified is the 16U processor that is responsible for the USB link... Kinda bad news as it requires a hot air rework soldering station to replace the part... You could get it off with a hair dryer (hot air) But likely a lot more than you bargained for in addition as well... Those devices aren't usually in the "Line of Fire"... Generally it would be the processor (the '328) and or the regulator... This is one of the Real Hazards of trying to use a servo, especially directly from the UNO board. I use qan external power supple that plugs directly into my breadboard power rails. Even with this setup there are big measurable losses. Losses in voltage are not necessarily bad, it's the things (breadboard and jumpers that are the issue) that cause the problems. Every thing you plug in expects clean 5V... If it's not there, neither are you... Fully. You Might also look at that cable thing that Liudr sells. I bought one and fell in love so don't take my advice... just look at it. A shield that plugs into the Uno and a cable and header to plug into a breadboard. Great for coupling signal pins (ports) but nearly worthless for Powering Servo's... use a separate Power Supply For the Servo and Always and couple ONLY Ground and the control pin and you should have much better results... IMO I don't use servo's but my analog devices work a whole lot better. Again IMO

Doc
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