GPS Problem (No, it's NOT the Flexcable!)

[Kuddel]

Hi Halftux,
I tried to find that TP_GAM_RESET but had no luck in the schematics it looks like that


but on my board it looks like this


could it be that the schematics are from a different version?

By the way to all who are interested in how gps chip looks like and to contribute to the discussion on this topic
http://www.motorolafans.com/forums/d...ps-a780-5.html

[Halftux]

Hmm strange looks like they removed the TP's. But it is pin 11 from flex connector (attached picture). Usually you shorten it to ground but could also be that you need to shorten it with another pin i dont realy know.

However you said gps were running yesterday for a short time. Hence I suggest an insulate contact.
So I would say it is realy a power problem or a clocking problem. Strace shows that the communication is ok until it should switch to operational mode.

• Primary Power Control: via the specific Operational Mode message
(@@Oa Position Request Message).
• Low-Power: RAM and RTC are powered; 32 kHz is the clock source for
RTC; wake-up via combination of serial RXD/MOSI
activity, timer external signal; lowest power consumption
mode.
• CPU Power: RAM, RTC, and the ARM microprocessor are powered;
main power level for performing non-position activities;
clock source is synthesized from 32 kHz.
• Full Power: RAM, RTC, ARM, RF front-end, and GAM are powered;
clock source is 12-26 MHz host-supplied TCXO; used while
the positioning engine is executing.

Test the gps in a warmer enviroment. Place it for some minutes on the heater in your room.

You could also make some pressure on some parts and test if gps is working again. If yes maybe there could be a micro crack in some soldering.

For resoldering flip chips you need a hotflow repair system.

By the way did you measured some voltage? I saw you removed the rf shield nice.
In the "reference guide v2"/"Instant GPS Design guide" you find some voltages and at the end the circuits.

Attached picture is from "Sch_A780_A2_C_L3_1.0.pdf"

[Kuddel]

Hi Halftux,
thank you very much for all these detailed information, but I don't have the equipment to repair my gps. I’ll try to buy an old a780 on ebay. Maybe I’ll find a cheap one with a broken display, but working gps. I thought I have seen the PCB on ebay but I can't find it at the moment. If anybody finds this PCB on the internet, then please tell me.