Mike Besemer - WM4B
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.