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Author Topic: Rigol DS2202A knob failure  (Read 1088 times)

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Offline v8daveTopic starter

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Rigol DS2202A knob failure
« on: September 27, 2021, 05:23:31 am »
Hi all,

I have a DS2202A which has an issue with 3 of the adjustment knobs. The horizontal time base scale and position knobs and the intensity knob all have the same issue. All of the others are fine.

When I rotate them, the count is random and jumps between up and down count making it impossible to set the time base and trigger center location. Same for the intensity knob when I try to use that for settings etc.

I've dismantled the front panel PCB to check and couldn't anything obvious. The intensity knob is hardly used so wear and tear don't seem to fit the failure mode. It seems to be something that is common to both but the PCB only has 1 FPGA handling the controls and all the other knobs and buttons are fine.

Anyone else had this before and found a fix for it before I decide to send it to Rigol for repair? It's out of the warranty period now.
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Online TheDefpom

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Re: Rigol DS2202A knob failure
« Reply #1 on: September 27, 2021, 05:34:55 am »
Just a complete guess, but it is possibly a power supply issue, could be noise on the rails.
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Cheers Scott

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Offline Circlotron

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Re: Rigol DS2202A knob failure
« Reply #2 on: September 27, 2021, 06:57:49 am »
Does the knob encoders have mechanical contacts or Hall effect sensors? I have a digitally tuned radio radio that has a pair of quadrature mechanical contacts on the tuning knob and the setting can be very jumpy, but if I rotate the knob a number of revolutions it comes good.
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Offline v8daveTopic starter

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Re: Rigol DS2202A knob failure
« Reply #3 on: September 28, 2021, 01:47:33 pm »
Quote from: Circlotron on September 27, 2021, 06:57:49 am
Does the knob encoders have mechanical contacts or Hall effect sensors?

Yes, these are the ones made by Alps. They are mechanical. I've used the very same units before in a design and they have been very reliable. This seems strange that only 3 of them are affected which sort of points to something being common but without a schematic or probing the PCB, not much I can do to diagnose it.

Rigol has offered me a new PCB assembly to fit myself so I am going to order this tomorrow. The price is about the same as I would end up paying for 3 new encoders and only a chance it would fix the fault.
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Offline v8daveTopic starter

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Re: Rigol DS2202A knob failure
« Reply #4 on: September 28, 2021, 01:48:36 pm »
Quote from: TheDefpom on September 27, 2021, 05:34:55 am
Just a complete guess, but it is possibly a power supply issue, could be noise on the rails.

Not really as the other knobs for the other controls are 100% fine.
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