Owon DS7102 – Rotary Encoder Noise Malfunction Fix

Hello All!

It has been a while since my last post. I had a lot to do all these days so my spare time was really cut down. In this post i'm going to write a small how to on how to fix possible rotary encoder problems on your OWON SDS7102 Oscilloscope. 

The issue:

Today while i was trying to read an analog signal using my OWON SDS7102 scope i realised that the Volts/div rotary encoder of Channel 1 didn't work as suspected. By turning the knob the value was jumping steps or do nothing ro changing direction. For example if channel 1 was set to 2V/div and the volts/div knob was turned one step right the value was jumping to 50V/div or to 20mv/Div or to another random value instead of 1V/div. 

In an older post i was analysing how a rotary encoder works. Brinking that post to my mind i thought that may be there is a filtering issue and the mcu reads most of the noise coming out of the encoder as a real output.

As a hardware engineer i always like to tear down the devices and see what is really going on inside. So i did and i reached the keyboard pcb.
OWON screws

After removing the backside of the scope you only need to unscrew the 5 screws shown in the above photo in order to reach the keyboard. 

Owon keyboard pcb backside

And… this is the keyboard back side. What i did was to solder two 100nF on each rotary encoder (one on each output) to filter the output signal. Each encoder has 3 pins in a row. The one in the middle is the GND and the other two on the sides are the outputs. As you can see in the above photo in the first raw i have soldered through hole capacitors and on the other two rows i have soldered SMD. Both types do the job and it's on your choice. 

After the reassembly of the oscilloscope i made a test and i show fully improved behaviour of all the knobs. The capacitors solved the problem and increased the quality of the knobs.

The conclusion is that the Chinese manufacturer may had chosen to make a software filter instead of adding these capacitors to reduce the cost but the software finally wasn't that good to filter all the noise. By adding these capacitors we reduced the noise going to the mcu from the rotary outputs and make software filter life easier. 

Now you can understand how important are the capacitors!

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34 thoughts on “Owon DS7102 – Rotary Encoder Noise Malfunction Fix

  1. Thanks for sharing .. i have had the same problems with my scope, with "knob board" of version 2.3. Your solution did work like a charm 🙂

  2. Dear Haris, I had the same problem with this scope, it was really annoying. However, my vendor offered me a replacement keyboard (before I found your blog) when I asked about this problem, and with the replacement, the problem is gone for now. So it seems not all of the encoders have this problem. On the old board, the encoders had an "Everbest" (how ironic) trade mark, the new ones are labelled "LJV".

    Just wanted to share this because I still think this is quite a good scope for the money (in spite of some software issues), but this encoder behaviour got me really frustrated. So people who buy this model new now hopefully get the working encoders.

    And if the new encoders still fail too early, I will definitely try your trick with the filter capacitors.

    By the way, my boards (old and new one) had the version 2.3 on them, so obviously they did some re-design of the board, but this did not affect the encoder issue.

     

  3. Awesome! I tried this on the horizontal position encoder and it did get significantly better, although still not perfect.

  4. Hi, I had a similar issue with an Owon scope. I made a test jig with a pair of LEDs. At first, the encoder was intermittant with random connections. After a while, it started working properly.

      My guess; The logic circuits do not impose enough current on the contacts to keep them "wiped" and by adding the caps, the instant current they produce being discharged is enough to keep the contacts cleaned.

      Just my thought, I am adding the caps you suggested to avoid having a repeat.

     

      Thanks for the article.

    1. Adding to the problen is the fact, that the rotary encoder seems to be integrated in a key matrix to save pins. So you have no static state for the encoder switches… If the "rowscan" and the state change of a rotary encoder switch are to close, they could "miss". The little capacitance seems to hold the state just long enough to mitigate the problem 🙂

  5. Thanks for the tip, adding the caps seems to have fixed the encoder jumpiness for me!

  6. Hi I just tried the fix with a V2.2 Button Board. The 100nF didn't work that well, but with 220nF it's stable.

  7. Thank you for this article. It fixed the issue of the rotary knobs. After 2 years, the DS7102V's rotary knobs were very difficult to use. So, like you did, I added these 100nF caps and now it's a lot better (but not perfect though). I'm really happy with the result.

    I would like to share two tips that could help when disassembling the backside of the scope :

    -The push button for on/off on the top side can be removed by pulling it. I recommend to do it otherwise, you might break a plastic part which is difficult to glue afterward (Trust my experience …) 

    -There are two others screws which are not visible in the first picture to remove on the left in order to remove the circuitry. These make a total of 7 screws to unscrew.

    Thank you again for this article.

  8. Add me to the list of happy users!  Mine was lousy from day one and only got worse.  Now the encoders work like a real scope.

  9. Thank you for the article!

    I own an OWON SDS8202V the marking on the encoder PCB reads SDS7102_KEY_V2.1 and 2012.02.25. After about one year the rotary encoder response became increasingly worse. I seems that contact bouncing or at least the applicability of the software filtering is a matter of wear in this case.

    Adding two 200nF capacitors to each encoder solved the problem completely. YES 🙂

  10. About the Encoders brand Evarbest.

    I changed the encoders but the new one turn inverse. Need to make a jump to connect right side to left and left to right.
    Only cut left and right encoder legs but left a short terminal to you can solder a wire and solder the another wire point to the other side pad in the PCB and do the same to the another leg.

    The problem about the encoders get fail is because they have grease inside to make they heavy to turn to do not turn easy. The grease is made of something meltable. It melt and flow to the encoder contacts and there do a film of insulation. If you can open the encoder and clean it with solvent, you will have it back in order to work for some time but you can apply some soft grease to give long life to the contacts.

    Thank you

  11. Have had this issue too.  At first the 100nf worked, but now the issue is back sigh.  Will try 220nf next. 

  12. My scope and I telling you thank you 🙂
    Due to missing required amount of caps used 220nF;330nf and 470nf.pairs.
    Can't see any siginificant diferene between them.

    Once agian, thank you.

  13. Hi Haris,

    My scope was sitting beside me last some years. I had replaced all RE but there was no luck at all, Today I tried have a look again and I found your article.
    Thanks so much, my DS9302 start work again.
    I forgot put C on multipurpos knob, I need open it again but this is just a small work and I'm more than happy I can use it again and I was wanted to say thank you to you before last C in place.

    Atsu
    5W1SA

  14. I checked the signals from the encoder with different capacitors with an oscilloscope and came to the conclusion that 1uf work better, they filter more bounces.

  15. I apologize for being misleading. 1uf capacitors filters better but, when rotating at high speed, they skip switching, it is better to use 100nf – 200nf.

  16. Dear Haris,

    after a long time of unuse I take my 7 year old SDS7102 back in hand and was surprised about the misfunctional knob encoders. Do I need a new scope?

    No! With your brilliant instruction I recover my scope. Soldering of 16 smd caps was little tricky and I need 2 hours for that, but at the end the scope run now flawless again.

    Thank you very much for your guide.

    Roland from Germany.

  17. Thanks for posting this!!

    It was not possible anymore to operate my scope because of this issue. I followed your advice, but used 470nF smd capacitors. This completely solved the issue on the 3 "big knobs" (amplitude ch1 and 2, and time), whereas the all others have improved significantly but are not perfect yet. However, I can use the scope again.

    Thanks,

    Walter

  18. I bought my SDS7102 about 4 years ago fresh out of basic electrical theory class, I love to tinker. It has set for several years as other things have taken all my time. Now that I have come back to it I am having issues as described here with the encoders. As stated before I am no electronics wizz . My question is what is the highest voltage these capacitors will see?  

    Would these be a good choice for specs and size? Mouser Part # 581-1206YC204KAT4A

    https://www.mouser.com/ProductDetail/AVX/1206YC204KAT4A?qs=sGAEpiMZZMukHu%252BjC5l7YYQ8%2FOavqLtR45E2GWR36ck%3D

     

    1. Yes there is only logic voltage there so it should be maximum 5V so the capacitors you are posting seems to be good. 

  19. I tried the fix, no real improvement on my SDS6062V.
    Anyone have information on information on replacement encoders?

    1. If you had a lot of months to use the Oscilloscope try to give several turns right and left of each rotary in order to clean their contacts (Oscilloscope switched off while trying this). Then switch on the Oscilloscope and everything should work as new. That is what i also tried after several months of no use and fixed the rotary malfunctioning

  20. Hi,

    Pulled out the Owon PDS 6062T oscilloscope and I’m finding it very difficult to adjust any of the knobs. I haven’t used it in several years, and it seems I remember it somewhat touchy when it was purchased new. The problem must have gotten much worse. I’m sure the warranty is gone. Just wondering if Owon would do anything for me since they must be aware of this issue? Has anyone repaired one of this model?

  21. Hi and thanks , your a genius !!!!!!. after many months struggling with the settings on my scope i finally found this website… she works like new , probably better than new .

    thanks

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