M4 beta : lost capacitor - help needed !

[Crizz]

Hey guys,

last few days i had the problem that GPS isnt working on my M4 anymore. Tried to check with the UBlox-Tool, but only strange values and no fix, sometime no data at all.

So i inspected the board a little more in detail and found a lost capacitor underneath my groundplane
( ssems to be c37 ? )

Have the beta-pcb from november 2014 , can anybody say what type of capacitor gots lost ? Have some SMD capacitors here, hotair also, so it wouldnt be the probloem if i know the correct type.

Please see pics attached for details.

[DUKE40]

Hi Chris,

you mean C37? I will see if I can identify on my M4 what component it is.

[Crizz]

i can only guess that it´s c37 , like on the picture to be seen, the silkscreen is broken by 2 vias, makes it harder to read. It´s the one above c33 . There are only the soldertabs of the capacitors left on the pcb. Guess it was result of a topdown landing.

[Kisssys]

That is C37 a 33uf tantalum. Digikey pn 493-3879-1-ND. Should not be the cause of a GPS problem. A common gps problem is the shield on the antenna is frayed. For some reason the pn does not come up correctly at digikey I'll see what the issue is. This should be a good substitute. 718-1672-1-ND If your not using the onboard receiver you could not worry about it.

[Crizz]

i use the onboard-receiver, so i should care for replacement.

Tried to place the GPS Antenna on one of the outriggers - but doesnt solve the problem, still no GPS-fix, no data. So guess it´s not a shield-problem, it worked for several flights.
Seems the Autoquad-controllers don´t love me. My AQ6 drove me nuts and isn´t still perfect, flying okay, but thats all, now the M4 is a pain in the neck.

okay, have to check where i can get such an antenna-wire and make a simple dipole to check if the GPS-antenna itself is the problem or the Ublox unit.

[Crizz]

found the problem with my GPS, the antenna was bad. Duke40 helped me with his spare gps antenna for testing, and with this one it worked well. So made a dipole for replacement until my 30 db antenna arrives.

Seems again like AutoQuads doesnt love me : even on my AQ6 the antenna is bad and the cause for switching between 2d and 3d locks - so need to be replaced also.

[LPR]

Every GPS antenna that stopped working for me had the shielding frayed where it's connected to the antenna. The cable on the GPS antennas gets frayed by handling or in a crash.

To repair the GPS antenna I remove the cable, shorten it and solder it back on. To stop the cable from fraying again I glue the cable to the antenna just after the solder connection for the shield.

Larry

[Crizz]

Wasnt the reason in my cases, Larry. Measured input resistance of antenne, around 260... 300 ohms, so there wasnt a broken shieldwire or shortcircuit between shield and centerwire.

with the small 10 mm antenna of my m4, i´m in doubt how to re-solder the wire manualy. Starts with removing the shield plate from bottomside without moving parts of the amplifier stage (bird-seed), and re-soldering the wire in this small size w/o melting the insulation between shield and wire is even sort of art. I admire everybody whos able to, to me it´s too small.

[chschmid]

[Crizz]

handshaking ? That´s earthquake....