BBB won't boot with K-8 cape installed

[Reuhlz]

How do you know when you have a bad K-8?

This is the second season I have wrestled with my K-8 that has never made it into service.  BBB boots up fine with the cape installed and 5v barrel power.  Once you install the cape only the single blue led by the barrel connector is solid and there are network lights on the RJ-45 port.  No activity at all on the other 4 BBB blue LEDs.

I have recreated the problem with multiple BBBs, multiple SD cards with fresh installed SD images (7.3, 7.5, 8.2).  Today was the first time I have separated the power from the 12V cape and the 5V BBB and could see the problem occur only when the cape was installed but boots fine with naked BBB.

Anyone have any diagnostic ideas I can try?  Thanks in advance. 

[dreiman]

If you are only getting the 1 blue led, and none of the other activity led's are going, then it's not even getting past post. The Network part of that board is separate from the cpu side of the board. It can power up even if there is an issue with the cpu. So something its shorting something out on the CPU side of the board when you plug in the cape.

This is what I would do.
First with a lot of light and a good magnifying glass, visually inspect the board. Look for cold solder joints, and any bits of solder that may be shorting.
Then I would get the pin out for the BBB, and I would check all the pins on the cape that connect to +v and ground to make sure they are not shorted. If there is a short, then something is either physically shorting a component or trace, or a component has failed to ground.

But honestly, it sounds like the issue is with the cape.  My first k8 didn't work. the fuse LED's lit, but the cape didn't do anything else. I got mine from wired watts. I let them know and they replaced it. It seems that every once in a while there is a bad one.

[Reuhlz]

I have multiple BBB that will boot into FPP when naked, but when the K-8 cape is installed I only get the single blue LED and no other blue LED activity.   

I purchased this from KulpLights directly (not wired watts).   I am just posting here in case the community has other ideas.  Knowing the busy time of year, I was trying to be sensitive to Dan's time.

[dreiman]

Hopefully Dkulp can chime in. Maybe there is a simple fix.

[EDIT]

Just found this.... try it maybe?

https://falconchristmas.com/forum/index.php/topic,14582.msg121178.html#msg121178

[Reuhlz]

I just tried that and no luck.   12V power to the K8, wait a few seconds then add the power jumper to power the BBB.   The single blue LED just has a slow flash with no other LED activity.

I also previously had the power jumper removed and was powering the BBB through the 5V barrel connection with a DC DC buck converter while the cape was installed with no luck.

Thank you for the troubleshooting tip.  Anything helps to try!

Edited:  Brand new K-8 just showed up from Wired Watts.  All power, connections, rj45s, pigtails all re-connected as I needed for my show and everything works and boots just fine into FPP.  Therefore my setup is validated to be good.

[dreiman]

powering the BBB through the 5V barrel connection with a DC DC buck converter while the cape was installed with no luck.

I don't think a buck can provide enough amperage....