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

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