OWON SDS7102V - problem with encoders

[mati998]

Hello

I have a very big problem with OWON SDS7102. I bought used oscilloscope without any guaranty but in pretty good price. It turned out that there is a strange issue: all of encoders don't work. I checked them using multimeter and they seem to work but there is no response when I turned them. I replaced IC's on keyboard PCB (2x 74hc4051d and 1 x 74hc393) but it didn't help. All buttons, including buttons in encoders works good, so I don't know what is a cause of problem. Could you give me some tips what I shold check becasue I really want to repair it. 

Edit:
I found the cause - there wasn't resistor R6 10k. I soldered new one and it seams to work. Now I'm going to do more tests.

[atferrari]

Hi there

SDS 7102V

Two days ago I noticed that the vertical control of channel 2 is not changing the VOLTS/DIV value in the expected sequence (1 2 5 or reverse). It even skip steps or returns to any possible value following no logic. A nightmare that took me several hours to identify.

Considering the encoder seems to go in mechanical steps, one at a time as expected, I concluded that it could be wrongly working software.

Any suggestions or comments? The local service (not exactly an official one, is not even answering the phone).

 

[mati998]

Hello

I have to admit that after soldering the resistor R6 everything worked but very, very unstable. I tried to understand what this key PCB works and I mesured signals going to U7, U26, U27. It turned out that on one of encoder (on input) instead of direct current there was very noisy signal (on my old analog scope it looked a bit like square wave). So i added two capacitors 100 nF between first and middle pin and middle and third and all knobs started working! Now i want to add capacitors on each encoder to be sure that it will be working correctely. It is shown there what to should do:
http://www.candrian.gr/index.php/owon-ds7102-rotary-encoder-fix/
Maybe it will be solution of your problem.
Good luck!

[scopeman]

IIRC Owon has a replacement board that is fairly inexpensive for this scope. I think it was something like 20USD a couple of years ago.

Email them and ask.

Sam
W3OHM

[MF-jockey]

The setting had also become impossible with my OWON SDS7102.
The reason for the operating problems is the grease in the encoders, which is intended to brake the rotation. Over time, it gets onto the contact tracks and causes irregular interruptions.
Cleaning or replacing the encoder is difficult.
However, you can manage with the suppression of contact jumps with capacitors (100 nF ... 1 µF).

For the repair I took 470 nF SMD capacitors (1206, 3.2 mm × 1.6 mm), you will need 16 pieces.
I first removed the battery-pack (without battery option remove the dummy cover).
I then removed the on / off switch cap and flipped the switch down before opening the case.
The rest is explained by the pictures below.

After about an hour of work, the oscilloscope works like new again.

[cncjerry]

Quick note for those that might do this in the future, though mentioned, pull the power button up out of the scope prior to trying to split the cases.  It does come out and off the switch post.   I broke my switch, superglue to the rescue, and a heck of a time putting the spring back into the switch.

By the way, I think I would use 470nf instead of 100nf if I had to do it again.


Jerry

[terry-moreau]

Had the same issue. For years I just kept turning my encoder at random (both directions) until by dumb luck I got the desire range.  I used thru-hole 0.1uF and it was an instant fix.  Someone mentioned that hardware/software debounce is inadequate or missing, and I suspect that's the case.  Some posted that they open their encoder; and cleaned out the grease, but to me that seemed like too much work and risked damage.  Another desoldered and replaced their encoders (with some debate on the replacement part#).  A good hardware debounce might also include series resistance, and even some added hysteresis; but I didn't want to cut traces or add any extra chips.

I suppose we risk some increased long-term degradation of the encoders contacts, by having it close a capacitive load without and in-rush reducing resistance (maybe 100R to 1K?).  When you can't scope the signal, and there's no schematic, it's hard to know exactly what's the best fix.

Thanks to this forum and the many posters that upload awesome photos, diagrams, links, and experiences/advice!!! 

[BritishGas]

I found 470n slugged the encoders too aggressively and faster movements of the knobs would not be registered.

100n is a good balance between speed of response and correctness of response on my scope.

Thanks to the authors above.