Velleman HPS140 MK2 Fault (Noisy Ringing waveform)

Hi i was wondering if anybody on the forum can help me please.I recently brought a velleman hps140mk2 of eBay used the oscilloscope seems to have maybe developed a fault.When I am using the test signal at the back of the scope i am getting a rough square wave the top and bottom flat part of the wave is very noisy but the sides of the square wave are clean I don’t seem to get this problem with my MK1 oscilloscope only with the MK2.On the 0.5v/div setting the signal is clean it’s only on the 1v/div and 2v/div the signal is noisy.The probe the that came with the scope is a Chinese P6100 and has a input capacitance of 90pf and not the original Velleman probe which has a input capacitance of 46pf i have even tried adjusting the compensation screw on the probe that has not made any difference i am still getting a noisy signal could this mean the probe is faulty or the input circuity to the scope
Thanks John.

Hello Johnci7,

Can you send us photos of this regarding this problem. as well as the test setup.
This way we have a better view of the possible error.

Best Regards,
Velleman Support

Hi i have included some pictures of the noisy wave i am getting from the built in test signal on the scope sorry for the poor picture quality showing the fault.The top and bottom of the square wave shows a lot of noise especially on the 1v/div it is much worse on the 1v/div compared to the 0.5v/div and 2v/div setting. The bottom of the wave also becomes cleaner as i change the time/div but the top of the square still stays noisy original i thought the test signal built into the scope was faulty so i tried feeding the scope a external square wave from a signal generator instead of using the test signal built in the oscilloscope and I am still getting the same results a noisy wave The probe i am using is not the original Velleman probe it a 100Mhz Chinese P6100 probe i am wondering if the problem could be with the probe and not the scope.
Thanks John.



The problem “noise on signal” may disappear if signal is shifted by Y position.
The noise on the signal can be caused when the AD converter just switches between many and few ones (e.g. from 01000000 to 00111111)

Best regards,
Velleman Support

Thank you very much for your help VEL450 i will try shifting the signal by the Y position hope this cures the problem.Thanks once again.
John Ioannou

Hi is there anybody on the forum that can help please.I posted a post 3 weeks ago about having problems with my Velleman Hps140mk2 used oscilloscope i brought of eBay.I am getting a lot of ringing noise on the square wave test signal built in the scope the signal is very noisy i have been told that the signal is normal because of the AD converter switching but every setting that i set it to I am still getting ringing on the waveform even if I put a external signal from a signal generator into the scope or even use the internal test signal built into the scope also the ringing causes the voltage at the bottom right of the scope to fluctuate very erraticly and i can not read the voltage properly because it’s not clear.Orignal i thought the problem was with the probe because it not the original Velleman probe so I decided to buy a new original Velleman probe to see if it was the probe and I found out it wasn’t the probe so then i decided to buy a brand new Velleman Hps140mk2 of Amazon which was on offer and my new Oscilloscope still does the same thing as my used Oscilloscope i don’t seem to get this problem on both of my HPS140 mark 1 scopes only on the Hps140 mark2 scopes i am getting ringing could the Mark 1 and Mark 2 have different filtering circuits i don’t
Know. If anybody can help me I would really appreciate it as I don’t know what to do anymore.
Thanks John