Repair help-Garmin Legend HCx not acquiring satellites

jtr1962

Flashaholic
Joined
Nov 22, 2003
Messages
7,505
Location
Flushing, NY
I purchased Garmin Legend HCx second hand in late 2009. The unit has mostly served me well. It even survived 3 falls while cycling (all due to the faulty bike mounting system Garmin uses, since corrected by making an aluminum mounting bracket). After the first fall in April, it worked, and then suddenly stopped receiving satellites. I opened the unit up to see what was wrong, but the problem seemed to correct itself. After this, the unit worked fine until today, although it had been unable to read the maps on the micro SD card since the 2nd fall in July. Tonight it simply did not acquire satellites even though it had worked just fine this afternoon.

I did some research. The problem is the result of chipset software somehow getting corrupted, sometimes as a result of turning on the backlight while the unit is booting up. It manifests itself as GPS Software Version 0.00. The usual fix is to reflash either the GPS firmware, or the chipset firmware. I tried multiple times reflashing the GPS firmware, even reverting to prior versions. The GPS firmware upgraded successfully every time, but the GPS Software Version remained at 0.00, and there was no satellite reception. I was unable to flash the chipset firmware. About 13% into the procedure, there was a failure to communicate. I did try a hard reset (page + joystick + on buttons) with no luck.

Is there any hardware repair which might fix this? Garmin charges $89 to basically send you a refurbished unit. It's not worth it to me to spend this much considering I only paid $80 for the GPS to start with. Also, I already fixed the intermittant contact problem by soldering wires from the battery terminals to the GPS board. I would most likely need to open up the replacement unit and do this because the stock battery contact set up is unreliable (it relies on pressure only to maintain contact). As a result, there are intermittant shutdowns over bumpy roads.

If all else fails, what are the best options for replacement? I basically just want something which works with the three bike mounts I have, and logs my rides in the same format. Used is fine, and the less I spend the better. I honestly hoped my HCx would have lasted a lot longer than this. The irony is as far as I can tell the GPS survived the falls just fine, only to be put out of commission by software issues.
 

jtr1962

Flashaholic
Joined
Nov 22, 2003
Messages
7,505
Location
Flushing, NY
I want to report that I was able to fix the problem by removing and charging the unit's internal battery. This is a small ~6mm diameter coin cell located near the ribbon cable connector for the micro SD card. I'm not sure if this cell is rechargeable or not. I do know that I measured the cell's voltage at about 0.25V. I desoldered the cell, and briefly applied 3V to the terminals to charge it up past 2V. Once I soldered the cell back in, the unit immediately acquired satellites upon rebooting. I was even able to successfully update the chipset firmware to the latest version (I had 2.40, latest was 2.80). I may or may not need a replacement cell, but at least I now know the source of the problem.
 
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