Hi,
I bought a brand new Rigol DS4014 back in 2016, but bad luck: it had a random failure where it was failing to boot. I sent it back to the reseller, and got it back under warranty a while later. Since the label at the back had a corner slightly bent (where the hidden screw is located), i believe they have change the motherboard.
Probe identification problem:
The boot problem was gone, but i've discovered a new problem: when connecting the probes, there are quite often not correctly identified, displaying sometimes bad ratio (1x or 20x instead of 10x), or sometimes bad type (active, Tek, 50 Ohms). But after repluging them several times, i manage to get it correctly identified as 10x Nor-probe.
I should have immediatly sent it back, but as once connected it stays OK, and because of various personnal and professional circumstances, i've used it more rarely that i was expecting, and i forget to do it, until the warranty expired
Yes, that is really stupid.
Does anybody have an idea of why the probe are randomly identified, and possibly how to fix it?
Fast forward to today: i still have this problem, but noticed some others.
Shifted levels + supposedly too high noise, and self calibration:
First, even with no probe connected, all channels were showing shifted levels, like if there was a DC component, whatever i selected DC or AC coupling.
The noise was also quite too high for me, since at the lowest 10mv/div, i have almost 20mVpp of noise, even when connecting probe's GND to tip.
So i wondered if i should do self calibration, but i'm a little confused about how to do it properly, and i haven't found any video on the Internets.
The scope asks to connect all five inputs (4 signals + trigger) to the "calibration signal".
My first (wrong) try was to connect all probes to the front calibration probe terminals. But it failed with "Selfcal connection error". But after that the levels were no more shifted!
But incomplete calibration was worrying, and reading the manual i understood that i should use the "calibration" BNC at the back. But there's one calibration output for 5 inputs ?!?!
Connecting 1 by 1 is not working. So finally i used a mess of T and I (male to male) BNC adapters + cables to distribute the signal to all inputs. And a mix of 75 and 50 Ohms, since it is all that i have at hand.
Despite being messy, it seems to work since it took about 20mn to complete without error.
But is it reliable? If not, how is it supposed to be done?
After that calibration, the level of noise if about 1.5mV when no probe connected (don't remember if it was like this before or has improved), but still almost 20mV with a probe grounded to itself. But i also notice that the signal is strange at the very center of the screen (see screen captures).
I haven't noticed that before, so could be because of the messy self calibration cabling.
Hot BNC connector:
And last strange thing: i also noticed that the front BNC connector of input 3 becomes quite hot, almost painful to touch. Is it normal with this model?
Conclusion: i feel pretty unlucky with my Rigol experience, with so many defaults/problems when i've bought a brand new unit to be sure to avoid any! And since i've not sent back the unit after its "repair", and now that the warranty is long expired, i'm afraid that sending it back for fixing it would cost quite a lot...
I'm not sure i would buy another Rigol scope if i decide to replace it one day...
But i hope that with the magic of the Internets and the help of some gurus here, i could may be fix (most) of the problems by myself!
Thanks!