Siglent SDS2104X weird behaviour on one channel

[newbadboy]

Measured with channel 1 connected to regular passive probe and had also ch2 with a current probe.

I saw that the damping menu for channel2 jumped between 1x and 10x without touching anything. I tried to set 1x and then it jumped to 10x and back sometimes. I then set 10x and then it jumped to 1x and back. It did it like 3-4 times then it took a while and did it again and so on.

It did the same if i had probe connected or not, and signal or not. I have had this scope a while and not seen this happen before. Is it some FW bug or something starting to go bad in the HW??

[tautech]

These DSO's have probe attenuation sensing capability therefore the only reasons for channel input attenuation to change is a probe sense pin is not making contact, its 10k sensing resistance is somehow faulty or there is some contaminant between the input BNC and the probe sensing ring.

Please also state the firmware version installed.

[newbadboy]

How can i check FW version?

[tautech]

Utility>Sys Info

[newbadboy]

1,2,2,2,R19


Ok, it has autosense. But should behave like that if nothing is conected.

The current probe might have some strange setting but it should have stopped jumping when i disconnected the probe?

[tautech]

The current probe might have some strange setting but it should have stopped jumping when i disconnected the probe?

Correct.

Check the input BNC's for rigidness...they must be very firm as they are chassis mounted however if they have suffered a knock they could be misshaped and partially contacting the sense ring.
Inspect the BNC's and scope input frontal area very carefully and ensure there is clearance between the BNC's and their sense rings.
Try ~10k between the rings and BNC shells and watch for reliable and repeatable input attenuation changes.

[newbadboy]

OK thanks.

If it will appear again i will try the 10K test.

[newbadboy]

Ok. So now i tester it more. It actually seems that it jumps around för all damping settings but 10x. There it seems kind of stable.

In first link below i have filmed it so it can be seen how often it jumps.

In the second link i touch the ring and bnc with 10k. It detects the 10k and is stable when its connected. When i remove the resistor it takes a short while and then it starts to jump around again.

So what's the conclusion. I still have 1month warranty left. Is this some known issue?

https://youtu.be/RuunnzPgM8c

https://youtu.be/IQ3T2fRGLWI

[tautech]

Is this some known issue?

No.

Never seen or heard of this before.
It is only channel 2, is that correct ?

In your videos seems the BNC's are not centered in the sense ring.
Can you confirm there is clearance all around the channel 2 BNC and to the sense ring ?

[newbadboy]

Yes only ch2 does it. Yes you are correct, looking closely none of the bnc connectors are centered 100%..But IF the bnc ground is somehow connected to the sensing ring it should be like the resistor connection but permanent. It should not sense when i'm connetcting the resistor. Or is it kind of coupling capacative since it's so close....
What the heck is going on with this scope?

[tautech]

Yes only ch2 does it. Yes you are correct. Looking closely none of the channels bnc connectors are centered 100%.. What does this mean? But IF the bnc ground is somehow connectdet to the sensing it should be like the resistorconnection permanent. It should not sense when i'm connetcting the resistor. What the heck is going on with this scope?

This is what we are trying to discover.

If you turn the scope to OFF and measure the resistance between Ch2 sense ring and the BNC while trying to wiggle/flex the BNC does the resistance change ?

I feel the clearance around the Ch2 BNC may be too small so any debris could make a tiny bridge and upset the auto probes sense. Do you have compressed air to carefully blow around the BNC but try not to blow any possible debris into the scope ?

The last question....has the scope been dropped or suffered some impact so the BNC's are not properly centered in the casing hole ?

Maybe a warranty repair is next ? 

[newbadboy]

Measured the resistance. It the same on all channels. Not affected by trying to wiggle the Bnc.

No the scope is as new and never dropped or so.

[tautech]

Send Siglent EU a message and point them to this thread.
https://www.siglenteu.com/contact-us/

[rf-loop]

When it is on and nothing connected to inputs. Golden ring +3.3V to BNC GND.

When scope is Power Off and all discharged.
DMM Diode measurement between BNC GND and this golden color "ring".  All 4 need display around same.

Something around 0.95V when + tip is BNC GND and other, + tip in golden ring something around 1.25V

[newbadboy]

I have contacted Batronix whom i bought the instrument from. I will send them this thread link also.

I measured the voltage on channels 1 3 4 it was 3v3 as pointed put. On ch2 it is 1.33v. So yea something has gone bad. I guess some internal voltage ldo/reference is bad so it measures wrong level and cannot determine what has been connected.. Glad at least this happened with in warranty time.

[rf-loop]

I have contacted Batronix whom i bought the instrument from. I will send them this thread link also.

I measured the voltage on channels 1 3 4 it was 3v3 as pointed put. On ch2 it is 1.33v. So yea something has gone bad. I guess some internal voltage ldo/reference is bad so it measures wrong level and cannot determine what has been connected.. Glad at least this happened with in warranty time.

>>>>> Repair Service  (if you have looked very carefully there is nothing conductive shit between BNC GND and this ring as @Tautech advised. This probe 10x multiplier recognize resistance..well..not..it look voltage, 10kOhm is just loading it and drops voltage down to 0.3V. But I do not know what are threshold levels, what is "unspecified" level area. . This physical insulation clearance between ring and BNC is bit small, without any true reason so very small conductive scintilla may generate problem.)

[newbadboy]

I will check once more under microscope if i can find something

[highpower]

Perhaps try slipping a strip of paper between the BNC shell and the sense ring and work your way around around the shell like you would when cleaning contact points in a switch or a relay? See if anything smudges onto the paper or if the paper can't get through the 'gap' in certain areas around the connector? 

[newbadboy]

So i checked it under microscope.  Could not see anything whatsoever. I also cleaned it with a fine electronic brush to be sure. Started the scope and The damping did not jump around. Measured the voltage it was now 1.51Vdc. So i decided to leave it on for a while. After 15min, still no jumping but voltage was 1.43. After waiting 20 more min   i went and checked it. It was now starting jumping but not so often. When i touche it with the multimeter probes it jumped alot and voltage was now around 1.38V so i guess the threshold is maybe 1.4v or so. Now I give up. Something is not ok and need to be sent on repair. Thx guys for your help! Feel shitty cuz this scope i actually the best i have tested in this price range.

[tautech]

So i checked it under microscope.  Could not see anything whatsoever. I also cleaned it with a fine electronic brush to be sure. Started the scope and The damping did not jump around. Measured the voltage it was now 1.51Vdc. So i decided to leave it on for a while. After 15min, still no jumping but voltage was 1.43. After waiting 20 more min   i went and checked it. It was now starting jumping but not so often. When i touch it with the multimeter probes it jumped a lot and voltage was now around 1.38V so i guess the threshold is maybe 1.4v or so. Now I give up. Something is not ok and need to be sent on repair. Thx guys for your help!

I know this scope quite well as I had a SDS2304X for ~3 years and never saw problems like yours or similar mentioned online. I popped the factory email on Sat for their interest but you will deal with their EU branch.
Your repair should go smoothly but dig out any purchase paperwork you have to provide proof of date of purchase.

Feel shitty cuz this scope I actually the best I have tested in this price range.

The newer SDS2104X Plus is even better for not much more and although it's badged as a 100 MHz DSO its BW is much closer to 200 MHz so they are supplied with 200 MHz probes.
Trouble is due to demand they are becoming hard to source in some places.

Good luck and keep us informed on the warranty repair.

[newbadboy]

Sure thing. I will keep yall posted.