No trace. it worked before

[vladion97]

Hello! i recently bought this oscilloscope . it worked for a periode of time and now it's broken.
It worked for a few days abnormal . The voltage at L1 is also -15 instead of the target of -8.11V. Rest of test points are close to target with 9V input. Any suggestions please ?
with battery i have all voltages normal, but with adapter 9v, 0.6 A i have -15V on L1 and other 2 components .
The 1khz test frequency appears on lcd but after i remove the alligator clip it goes crazy and when i touch the red clip it appear a strange wave form.
PLEASE HELP

[MNTech]

Have you checked the voltage out of the AC adapter? An unregulated supply can go as much as 40% higher when lightly loaded. I connected 12V to my DSO138 and measured -15V at test point V- ( L1 ). 12V is the upper limit of the power supply voltage specification. The regulator will run warmer but it should be OK.
It's normal to pick up some stray voltage when the red lead is not connected to anything. If you touch it you are acting as an antenna and are probably picking up power line voltage.
Touching the red lead to the black ground lead will eliminate that noise if everything else is OK.
If your problem is something else please provide a more detailed description or, even better, attach photos.

[vladion97]

I have the same issue like this.
https://www.youtube.com/watch?v=AC7jbPC9HWE
I checked the voltage of the AC adapter and it has 9.2 V

[MNTech]

Try restoring the factory default values. Hold down [+] and [-] buttons simultaneously for 2 seconds.
Then do the Vpos alignment.
That worked for me when the trace was stuck at the top of the screen.

[vladion97]

it didnt work...i see a square wave just on 10Mv . But i cant change it..just the frequency