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Precision clock - half digits turn on
breadstock Posted: 29 Jun 2022, 07:45 PM

Posts: 1
Joined: 29-June 22
I'm very new to electronics and can't find where I've gone wrong.
Only the digits before the GMT/BST are lighting up and the GPS module LED lights up but not the GMT LEDs. Which bits should I be looking at to find the problem?

Last edit by breadstock at 29 Jun 2022, 08:11 PM

mit Posted: 30 Jun 2022, 11:27 AM
yeah whatever

Posts: 541
Joined: 4-May 16
This is most likely a soldering problem on the display driver chip for the side that isn't working. It can probably be fixed by re-soldering the legs of the MAX7219 chip from the component side.

I would first look closely to see if any of the joints have obvious problems - feel free to share a closeup picture and I might be able to spot something. The most likely pins to have problems would be LD_TIME or SPI_DATA:

(User posted image)

or here:

(User posted image)

I've put an online interactive schematic here: which can be useful for tracing out connections. If you have a multimeter, you can use it in continuity mode to check there is continuity between the display chip's pins and the ATtiny.


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