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Re: [Paparazzi-devel] YAPA v2.0 Hardware failures


From: Christophe De Wagter
Subject: Re: [Paparazzi-devel] YAPA v2.0 Hardware failures
Date: Fri, 29 Jun 2012 10:21:06 +0200

Exploding the big yellow cap on the bottom is someyhing  I have seen a few times around me. There is only 1 way to achieve this and that is to reverse polarity from the main battery. Yellow tantalum capacitors do not like reverse polarity at all as you can see. After such a mishap you (only) need to change the cap and the pth08080 module and clean the board with acetone to get rid of the smell. The rest is still OK because the active dcdc does not start making any voltage on the 5v when reverse polarized but just burns.

Concerning the not working servo's, .... yapa gives pulses to the servo's using the servo5v rail. So if you do not connect the servo power rail then your receiver will not be powered and with a scope you will not see any servo pulses either, so it might look like something is broken. Not sure this is your case but this has been reported before.

One possible scenario that could cause some of your symptomes: yapa was not designed to work with 7+ volt servo's. If you power your servo's directly from a 2 cell lipo for instance that might go wrong. I should look into it if this is the case as it depends on the actual chip being populated on the board.

In any case you should fully understand how to power the several subsystems of the board. Yapa has several options making it more powerful but also slightly more difficult. Paparazzi autopilots do not have the same amount of protection from abuse as some other consumer electronics so you must check what you do before powering things up.

On Jun 29, 2012 5:29 AM, "Romney, Jefferson S" <address@hidden> wrote:
I remembered somewhat wrong. I went back and looked at them again. There are four that have gone bad:
1. This one happened just as I said. the 5v regulator went bad like you mentioned, and the 3.3v line is shorted to ground. but the 5v line is not shorted.
2. This one turned on, but gave bad pwm signals to the servos. as far as i remember, this one never actually quit completely.
3. This one a wire came loose and shorted so no question there.
4. on this one I plugged it in the other day and c38, the big capacitor on the bottom went up in smoke. battery voltage is shorted and 5v is shorted but the 3.3v line is not. my guess is that this may be a short in the power supply as well.
5. This one I thought had done the same as #1 but on further investigation, i found it was the barometer not the autopilot itself. when I unplugged the baro, it worked fine.

I guess I really only have questions about 1 and 4.

Thanks,
       -Jefferson Romney

________________________________________
From: paparazzi-devel-bounces+romneyj=address@hidden [paparazzi-devel-bounces+romneyj=address@hidden] on behalf of Chris Gough [address@hidden]
Sent: Wednesday, June 27, 2012 9:14 PM
To: address@hidden
Subject: Re: [Paparazzi-devel] YAPA v2.0 Hardware failures

I've never seen that before. How does the power supply smell?

Chris Gough

On Thu, Jun 28, 2012 at 12:50 PM, Romney, Jefferson S
<address@hidden> wrote:
> I have been using Yapa v2 autopilots and loving them, but I have had some of them fail for no apparent reason. has anyone else seen this?  Usually it works once, I unplug it, and plug it back in and nothing turns on and it won't work again. Any ideas as to how I can prevent this?  Thanks for any information.
>
>  -Jefferson Romney
>
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden
> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel



--
.

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