For many years I have been using a M-241 GPS data logger for photography. It is really well designed, compact, and has a useful display. But only -158dB of sensitivity and 32 channels. It was time to look for something better.
I settled for a Transystem 747ProS using a MTK-II chip. Well, the documentation is ridiculous, and the LEDs are not self intuitive. But at the end I found out the configuration which I need for constant rate GPS logging. Via software setup, I disabled the “smart” function of the car and of the smart modes. I think, I could as well have bought the 747Pro (without the “S”).
What is the easiest configuration for logging? Put the switch only on “smart mode”, because the car mode requires external poser (via usb) otherwise it goes into sleep. The relevant information is given by the yellow satellite LED, continuously ON means looking for a fix (not logging), blinking means it is working, meaning it has got a fix and is logging.
Next step was to totally disable the buzzer and make that yellow satellite LED a little bit less brighter. First thing, remove the battery and open the housing. I pushed an old credit card between the two shell parts of the housing, starting from the side which is away from the LEDs – the strongest clips are closer to the LEDs, as one can see in the photo below:
Next step is to have a close look at the PCB and find out where is the best location to mod it. Initially I wanted to add a switch to change between the original mode and the no buzz/weaker LED mode, but I had no small switch available, then I just went for the moded version. The photo below shows the PCB and indicates with the red arrow where to cut the track for the buzzer and the yellow LED’s 220 Ω resistor.
Here you can see the detail. The buzz part is easy, just cut the track. I replaced the 220 Ω resistor with an 1 kΩ resistor that I removed from some scrap I had at home. The resistor is really small, therefore make sure you know how to (de-) solder it, you can get some scrap PCBs and do some training first. 1k is a bit too weak for outdoors but perfect for indoors.
That’s it. Now just but the top of the switch back, close the housing, add the battery, and there it goes logging!
I still wish that Holux would make a new M-241 with a better GPS chipset though.