Problem with GPS acquiring

[xXxav]

Hi Typhoon H pilots,

I'm Xavier, I live in France and I just buy a used Typhoon H with some problems.
Firstable, I upgrade the ST16 and the H with the lastest firmware : 3.04 for the H, and 3.1.b30 for the ST16.
Everything seems good, link to GUI to verify all the organs, and everything is OK.
But when I decided to fly, I always have this famous "GPS acquiring" and no way to have a ready signal. I read all the post on the forum (and the internet !!), I try many many thing : fly with FC1.26 --> very bad idea :/ but no way, no GPS lock. I decided to open the H, change the GPS battery, remove FC Board during 1/4hr, replace on, ... and I discover on the flight controller board that a component has a little scratch of burn ... I take some photos with a electronical microscope, let's have a look :

I search a datasheet on the internet and it could be a multiplexer 8 to 1 channel.
I know there are on the forum, some persons which are very qualified in electronics. I would like trying change this chip, I'got the material for (hot air pulse station, and a very good solder station)

Where can I find this component ? Do you think if I change it, the FC will good ?
For the person who had change their FC board for similar issues, can you check on your FC board if you see something strange on this chip ?

Thanks for help and sorry for my very scolar English !

xXx@V'

 

[Vaklin]

Where you're watching this "burn"? The IC is in a perfect visual condition.

 

[xXxav]

No the strange mark near the "56K" is a burning trace. The IC is perfored, it's not evident on the photo but I'm pretty sure !

 

[Vaklin]

This is a print with white paint. Manufacturers logo.

But if you're "pretty sure", with what we can help?

 

[Steve Carr]

Is this the spot that looks burnt?

 

[xXxav]

Exactly !

 

[xXxav]

@Valkin : No this is not a manufacturer logo and you can help me saying where I can find this IC, and if I replace it, do you think this will be functionnal ? And is it really an 8 channels multiplexer ?

 

[Vaklin]

Somewhere in the forum someone has posted schematic diagram. There will be visible what is this IC. Very possible is to be 74HC151.

Replacing will not improve the GPS status.

I can't take a photo with my phone, but the same mark is present on the IC in the FC, which I have here. Tomorrow I can check one more.

 

[xXxav]

Ok thanks for these informations, I'll check for these diagrams. I think too it's probably a 74HC151.

But why are you saying that will not resolve my GPS status ?

Is it a functionnal FC board ?

 

[Vaklin]

Post in thread 'Typhoon H 480 PX4 v1.10 (Stability issues ;-)' Typhoon H 480 PX4 v1.10 (Stability issues ;-)

 

[xXxav]

Thanks !

 

[dylanfm]

@Valkin : No this is not a manufacturer logo and you can help me saying where I can find this IC, and if I replace it, do you think this will be functionnal ? And is it really an 8 channels multiplexer ?

That is the Texas instruments logo. You can see it in a picture here:

SN74HC151PW TEXAS INSTRUMENTS - IC: digital | 8 to 1 line,multiplexer,data selector; SMD; TSSOP16 | TME - Electronic components

TEXAS INSTRUMENTS SN74HC151PW | IC: digital; 8 to 1 line,multiplexer,data selector; SMD; TSSOP16 - This product is available in Transfer Multisort Elektronik. Check out our wide range of products.

www.tme.eu

But like others have said, the chip doesn't look bad and I would doubt that this multiplexer has anything to do with the GPS.

Dylan

 

[xXxav]

Ok, you convinced me, but I will continue my research because I don’t understand why leaving the H for a while can cause instability on the flight controller.
Is this software, or hardware?
I would really like to understand.

 

[h-elsner]

The multiplexer tell the processor with what ESC he is communication via data buffer 74HC244. If there is a problem we would see it in GUI when testing motors/ESCs.

I'm still thinking it is the IMU that runs out of calibration values that can be corrected by the firmware.


br HE

 

[xXxav]

Thanks for these precious informations.

I'm still thinking it is the IMU that runs out of calibration values that can be corrected by the firmware.

This is what I think too : I try to reset the FC by downgrading in 1.28 but I always have a negative altitude and GPS acquiring. With the 1.26 version, everything seems fine : positive alt and GPS ready in 4 - 5 minutes. But we can't fly with this version, it's not safe.
I don't know what's wrong by upgrading after these versions.

 

[Steve Carr]

I have very little to add on the technical cause of this problem. However, all the faulty FC's I've changed in the past were from aircraft that came from a hot climate or were stored in a hot location such as the trunk of a car in the hot sun. Many were from Texas, Arizona and California. The sole exception was one from Ireland.
The inside of the airframe can get extremely hot when sitting on the ground in direct sun on a hot day. And it can get very hot after landing because the battery is below the FC. So after landing I remove the battery and set the H in the shade while it cools.

 

[xXxav]

I agree with that and I've already read something about overheated H. But I don't understand how an electronic component may be overheated so easily ...

Unless that would be the IMU (suppose he's very sensitive to heat) as says h-elsner. But why news FC boards are not faulty ? Does Yuneec change something on it ?

 

[slw74]

I had the same problem with one of my Typhoon H. In my case both the GPS board and the flight controller (FC) were bad. I changed them out one at a time, but the GPS did not acquire and give a Ready signal until I had replaced both. As Steve Carr indicated, I believe it was due to flying on a very hot day and having the H in direct sunlight just before the flight. That drone continues to do well.

 

[h-elsner]

I don't believe in overheating. IMU likes heat. The is a switched IMU heater inside the brass part. It is powered by 5V and controlled with one switch wire from processor pin PB4.

It looks like heater is (or should be) switched off at 39 or 40°C according the temperature value in GUI.
br HE

 

[xXxav]

So the IMU take a heater inside ? What's the utility ? Flying by cold weather ? Where do you see this temp value in GUI ? Is it programmable ?