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QLG1 GPS - No TXD


Mike Besemer - WM4B
 

Greetings all,

Working on a QLG1 for another gentleman and would like the opinion of others.

Initial symptoms were that the Power, TXD, and PPS LED all remained on at all times.  I received the board in the mail today and went straight to work on it.

A quick check with a scope revealed that there was no TXD or PPS output from the GPS RF Module.  I then proceeded to touch up all the solder joints, followed by a good cleaning with brake cleaner and a toothbrush.  This resulted in no change (as expected).

Based on measurements taken by the other gentleman – and my gut – I then proceeded to remove and replace IC1.  (I actually replaced it with a socket, to facilitate further troubleshooting.)

With the IC removed from the socket, I still had no TXD or PPS signal and began to suspect the RF Module, but a quick continuity check between the Patch Antenna and Pin 11 of the RF Module revealed a questionable connection, so I sucked that joint clean, scrubbed it, and resoldered.  A minute or so after reapplying power, I started to get a good PPS signal, but no TXD.  With IC1 installed, I get a flashing PPS LED and no TXD LED.  (Power LED is fine.)

If I remember correctly, the PPS signal should not be present until the constellation data has been downloaded and TXD is available and being sent, so I have to *ASSUME* that the RF Module is working insomuch as it has the ability to receive and decode GPS data.  That being said, it is still *NOT* producing TXD.

So the question is:  Is the Rf Module toast, or is it a firmware issue?  I tend to think the module is toast, but I’m not that experienced with chips that contain firmware.  I *COULD* drag out an rPi and monitor, download the image, and attempt to reflash the module, but before I go through all that thrash, I’d like to hear from others who may have been down this road. 

I’m aware that there is a pin-for-pin compatible replacement for the YIC, but IIRC, it costs more than the entire GPS.  I have the ability to replace the YIC, but I don’t know if it could be sourced from Hans or if that would be cost effective. 

Ideas?

Mike

WM4B


Armin, DJ2AG
 

 Hello Mike,
 
the yellow (TxD) LED should start blinking after power is applied.
 
Armin, DJ2AG