The replacement LCD has arrived. I take extra anti-static precautions and fit the LCD. Finally, the oscilloscope works. Sort of...
http://bit.ly/1RzsbiM DSO138 DIY Digital Oscilloscope Kit Electronic Learning Kit
http://bit.ly/1RzsbiM DSO138 DIY Digital Oscilloscope Kit Electronic Learning Kit
Looks to me that the signal processing circuit is off spec. If you can locate the SP circuit you might reduce the noise with a better RC signal circuit cap or by maybe adjusting the amplitude across the signal peek on the board or tap into the display signal and see if you can break it out to another display with a filtering circuit as to find the faulty component(s) It may be a single cap (just a guess on that). Anyway the top scan points seems to be in the wrong amplitude range, their changing, thus, unstable as it draws the scan line. Looks like an ampliture issue at the peek of the cycle. should be an easy fix. Thats providing the verticle scan line is actualy using real inputs and is not just a line(x1,y1)-line(x2,y2) style static command.
but that's a cool issue, fun to fix. I'm not sure what IC's are being used, if it has a microcontroller or some sram, I would dump the core and reflash it where there are suspect commands. Oh, heck, I just read below that it was a resistor issue, well, I was close 😉
You can calibrate on that green capacitor
Other videos I have seen appear to have the coupling switch set the 'gnd' position before connecting to the test point to calibrate the scope. Don't ask me what it does, but noticed yours was not set in the same place. Thanks for the info and troubleshooting. I think I might pick one of these little toys up to play with, appears they do a 'mini' version now, which just appears a little more finished.
very interesting video's thank you i only bought this kit as soldering practice ive never used an oscilloscope before but this was interesting as you had some problems like i did but not exactly the same
What wa sthat crap at the first 20 seconds of the video? No one cares. Just get on with what the title says it is about and quit wasting our time.
I have a problem with my DSO138
The trace is sort of visible, but it’s really high up, and I have to go to the left arrow and bring the “middle point” down by holding the correct button for more than 10 seconds.
Anyone know what could be wrong? It’s been working for quite a while before that.
2 Months ago I got one and all the surface mount components were already in place, the screen was in an anti-static bag and there was no interference on the wave form. So they must have taken your advivce as well as updating the circuit. It is a handy second scope.
Why do you waste your time on stuff like this?
Mine looked exactly like yours when I built mine. I did the noise mod on the board that seperates the analog from the digital ground. It halfed the noise. Still not a fantastic scope, but it really did make a difference, and only takes a few mintues to do.
Could you review the new DSO138 mini 13805K Version and compare it to the old version?
Clearly your problem was your LCD mounting pin orientation…
I saw one build where the culprit was the 7905 neg. voltage regulator. I*t failed fifteen seconds after he turned on. Check the regulator and it was defective..