EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: Peter_A on December 02, 2018, 08:13:27 pm
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I recently got an Owon PDS 6062T scope of eBay for 150€. I bought it as a defective unit, didn't really know what was wrong with it, but on the pictures it looked fine. It came with the original box and still had the wrap protecting the screen on, but sure enough it was defective. The problem with it is, that you cannot adjust its vertical position, it's stuck at a certain level and that level changes when you change the vertical scale (volts per division). As can be seen in the following videos (excuse me for fumbling around, I’m not used to this scope).
https://streamable.com/0enng
https://streamable.com/xhl73
Interestingly though, the problem goes away in single shot capture mode:
https://streamable.com/5389c
Has anybody encountered anything similar before? I haven't got the faintest idea what could be causing it to act this way.
Otherwise the thing isn't built all that well, the screen is kind of dim, and the user interface as well as some design cues are ripped off from the Tektronix scopes, but it would make a nice, cheap and simple carry around scope, since it can operate of a battery.
A teardown will ofcourse follow if anybody wishes to see it.
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Single Shot = Stop mode --> positioning the trace in Stop mode is just a graphical task within the screen buffer, hence software only.
Normal Trigger = Run Mode --> now the position control has to add a real DC offset voltage to the input signal, this is very different.
So it looks like there's a Problem with the internal position offset voltage generation/application. Could be the offset DAC or one of the OpAmps - there could be one for the DC input path and another one as a DAC output buffer. Of course also any other associated components/connections.
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This scope is really basic.