K8035 Up/down Counter Timer - Digit & clock not working

K8035 Up/Down Counter/Timer
I bought this kit a couple of weeks ago and upon testing, found that it did not work - the high digit did not display and the internal clock was not running. I looked on the forum and found a snippy answer about the internal oscillator and just use the dip switch. So I then spent half an hour removing components and testing them, only to replace them as they turned out to be perfectly fine. Upon further investigation with a DVM however, it became apparent that voltages and frequencies that should have been appearing on certain pins were not there. I then looked at the PCB and found that an artwork error had caused the PCB to be etched with 2 or 3 tracks broken. I repaired these by scraping the solder resist off the ends of the broken tracks, wetting them with solder and used short pieces of cut off component leg to bridge the gaps - care (and a magnifying glass) is required to not make a big solder blob of it all though. Kit now functions like clock-work… I’ve taken a picture of the board and position of the repair, but don’t know how to add it to this post, sorry. Any road, look along the tracks for pins 8 and 9 and the large plane below it, if there is a break, there’s your problem.

Happy days.


If it ain’t broke, don’t fix it.

Sorry to read that the PCB was at the cause of troubles.
It is very rare that there are etching errors on a PCB.
Anyway, we will inform our PCB manufacturer.
Happy to read that you were able to solve the problem.