JYE Tech Forum

Thanks Dave, and thanks for your feedback on trying other "fixes" to the noise issue.
Yes, unfortunately, my kit turned out to be a counterfeit kit with the attendant issues of wrong components and dodgy layout

I experienced high output voltage at TP25 from the negative voltage converter due to an incorrectly supplied 1mH inductor (L2). It measured only .1mH (100uH) and this caused a much higher than expected voltage. I suggest you replace L2 with a 1mH inductor. You may also find that Q1 (8550) has been d...

Thanks to MorganFlint and nurbard at the Banggood forum http://forum.banggood.com/forum-topic-61279.html?page=3 I was able to apply those mods to my DSO138 to good effect. I would estimate that this mod has reduced the noise evident in the display by 60-70% which is a significant reduction. For anyo...

Just wanted to update my previous posts to say the discrepancies with my kit were in fact due to the kit being a fake/counterfeit DSO138 kit from ebay. For those concerned about legitimacy of their kit, it appears the tell tale signs of a fake are: 1. thin/poor screen printing on the pcb 2. pin 19 I...

Hi again,
Have just located the problem with excessive output from the buck converter. The kit was supplied with a 0.1mH (100uH) choke for L2 instead of the 1mH that it should have been.
This low value inductor was responsible for the high negative supply voltage from the buck converter.
Grant

Firstly, thanks for a great design. However, like Allan, my kit had the wrong components - specifically the transistor for Q2 (9014) - a 9012 PNP was supplied. I assumed that it was a suitable substitute when assembling the unit, but at first power up, Q1 was overheating badly. Some time checking th...