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RCP2 Hardware Issue -Power Cycles repeatedly, Cannot connect
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Post RCP2 Hardware Issue -Power Cycles repeatedly, Cannot connect 
Out of no where I'm having very strange issues with my RCP2.

When I plug in 12V the LEDs come on for a split second then everything shuts off. This keeps cycling about once a second.

I measured voltage at the imput and its 12.5V with it not connected to the RCP.
When I connected it to the RCP it oscillates between 0 and 0.5V in sync with the LED lights.

When I plug in the usb COM port it repeatedly connects and disconnects (I heard the windows usb chime) but it never connects and I never see it on the device manger.

I opened it up to see if I can see and damaged components or see if anything is shorted and drawing to much current.

The only suspect component is the L3 inductor (pic attached ). It gets pretty hot. The voltage regulators are all cool to the touch.

Any advice on what might be the problem and how I might fix it?
I'm capable of replacing SMD components. I just need to know what steps to debug and what to order.

Thanks in advance!

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pic attached (where the black tube is pointing at)




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Correction, it is the IC U7 right bellow it that seems to be the issue.

It is on FIRE. I'm pretty sure it's shorted. Could you please provide the part number so I can order a replacement and swap it out?

It looks like it might be this guy?

http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/FAN8303MX/?qs=2yL51YY%2FFPWBAb6foqLsBQ%3D%3D

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Hi - sorry you're having these problems. Let's figure it out.

Yes, it is a FAN8303 - easily obtainable as you've found.

Question, did you recently have a low battery condition where you needed to jump the battery, or any alternator faults?

The issue is either the chip went bad, as you suggested, or there's another short downstream. If you remove the chip and supply *regulated / current limited* 5v to the board (on the striped side of C41) that will provide a hint.

Failing that, we'll be happy to inspect and repair as needed. Please keep us posted.


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Thanks for the reply Brent.

No this all happened on the test bench. Device was powered from a regulated power supply set to 13V.
The only thing that changed was I powered an auxiliary device from the 12V pins on the CAN Ethernet connector. That device might draw 0.5A at most.

Would this extra load on that circuit cause failure of any component?
If the RCP2 is only connected to the usb and I power a device using the 12V on the CAN port will there be any issues?

If the simple chip swap doesn't fix the issue I'll try powering it through C41 as you suggest.


brentp wrote:
Hi - sorry you're having these problems. Let's figure it out.

Yes, it is a FAN8303 - easily obtainable as you've found.

Question, did you recently have a low battery condition where you needed to jump the battery, or any alternator faults?

The issue is either the chip went bad, as you suggested, or there's another short downstream. If you remove the chip and supply *regulated / current limited* 5v to the board (on the striped side of C41) that will provide a hint.

Failing that, we'll be happy to inspect and repair as needed. Please keep us posted.


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500mA load on the RJ45 won't affect the rest of the circuit.

If you're game, try feeding 5v power directly to the 5v bus of RCP without powering it with 12v. Pretty sure you don't need to remove the FAN8303 for that.

Could be the FAN8303, or the inductor. Thanks again, and if at any point you need us to help directly, just let us know.


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brentp wrote:
500mA load on the RJ45 won't affect the rest of the circuit.

If you're game, try feeding 5v power directly to the 5v bus of RCP without powering it with 12v. Pretty sure you don't need to remove the FAN8303 for that.

Could be the FAN8303, or the inductor. Thanks again, and if at any point you need us to help directly, just let us know.


Hi Brent,

I finally got around to replacing the FAN803. But it did not solve my problem.

When I plug in the USB I get no COM activity at all on the device manager tool.

I used an thermal imaging camera on it to see if anything looked unusually hot. The micro controller gets pretty warm (120F or so), but the U8 IC below it is on FIRE. I can't get a temp reading on it since it's too small but it's significantly hotter than the micro controller.

Any advice on what to try next in troubleshooting/repair of this board?




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Hi, looks like the 3.3v rail is shorted. With the processor heating up, I wonder if something happened to it.

Just before it happened, can you describe what kind of sensors and connections you had to RCP?


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brentp wrote:
Hi, looks like the 3.3v rail is shorted. With the processor heating up, I wonder if something happened to it.

Just before it happened, can you describe what kind of sensors and connections you had to RCP?


This happened on the bench. I had 12V and GND connected to the screw terminals, and I connected an auxiliary IR tire temperature system to the RJ45 port (CANH, CANL, 12V. GND)

No other sensors were connected and I've never had an issue with the hardware up till that point. I've used the tire temp system connected to the RCP CAN bus a few times before without any issues.

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Hm. The processor should be buffered by the CAN transceivers, so not sure what happened there - very odd.

We will be happy to look at it and quickly turn it around - if it happens again we should trace the circumstances and steps exactly, if possible.

If you'd like us to look at it, email [email protected] and we'll take care of you asap.


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brentp wrote:
Hm. The processor should be buffered by the CAN transceivers, so not sure what happened there - very odd.

We will be happy to look at it and quickly turn it around - if it happens again we should trace the circumstances and steps exactly, if possible.

If you'd like us to look at it, email [email protected] and we'll take care of you asap.


emailed. thanks.

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Thanks, we'll update as soon as we can.


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