Leader oscilloscope 1021 time and volts knobs

[tonedeak99]

Hi everyone. Was hoping to get some advice on how to clean the internals for these knobs. When I switch to different times or voltages there is some noise or artifacts that gets put on the waveform. I think the contacts may be dirty. Ive read some recommendations for Deoxit and others for IPA.  The noise is pretty minimal at the moment. Pics of both types of attached.   Thank you all for your help.

[bdunham7]

Is the noise or whatever there only AS you are switching the controls and then as soon as you're done it goes away?  In that case, leave it alone.  However, if you have to wiggle the controls to get a good clean signal, then perhaps some IPA on the open switches.  I'd still leave the enclosed ones alone for now.

[tonedeak99]

Noise comes in the form of random artifacts on the CRT screen that are not part of the waveform. 

Some wiggling of the timebase knob at settings like 1 and 2ms is sometimes needed to get a stable waveform.  For the most part no wiggling is needed as it usually corrects itself once you stop touching the knob.  Light to medium touching of the knob will re-introduce the noise.  The voltage knob only has noise in between changes of its setting.

Also on an unrelated note is this square waveform normal?  Why the ripple?  This is coming from my phone's signal generator app.

[TERRA Operative]

I use Deoxit D100L in a Hakko FS210 flux pen to clean these (very carefully!)
I wipe the contacts with the pen then clean the pen with isopropyl on a Kimwipe, rinse and repeat until shiny.

Don't wipe the last bit of Deoxit off the contacts and you'll have happy switches for ages.

[tonedeak99]

Disregard the question about the square wave.  Found my answer.  It's the phone.  I need a audio generator to make cleaner waveforms.

https://audiokarma.org/forums/index.php?threads/oscilloscope-basics-part-4-square-wave-testing-and-analysis.850773/

[bdunham7]

Some wiggling of the timebase knob at settings like 1 and 2ms is sometimes needed to get a stable waveform.  For the most part no wiggling is needed as it usually corrects itself once you stop touching the knob.  Light to medium touching of the knob will re-introduce the noise.  The voltage knob only has noise in between changes of its setting.

If they're open and accessible, cleaning with IPA and maybe applying Deoxit may help, but use very small amounts of either!  Or, you may find that the switches get better with some use.  Noise while you are handling the controls is fairly normal, having to wiggle it to get it to settle is is not.

[tonedeak99]

Thank you all for the wonderful advice.  I only cleaned the timebase knob which has exposed contacts.  I tried IPA with a qtip, let it dry and tested it.  Qtip did get dirty but all the noise is gone.  No need for Deoxit!

[BlownUpCapacitor]

This is coming from my phone's signal generator app.

Can't you just use the probe calibration 1kHz square wave signal for that? I promise you, if the calibration generator works fine, the signal from it will be 2.87548x10^69 times better than your phone's audio output.

[tonedeak99]

This is coming from my phone's signal generator app.

Can't you just use the probe calibration 1kHz square wave signal for that? I promise you, if the calibration generator works fine, the signal from it will be 2.87548x10^69 times better than your phone's audio output.

Yes and that works fine.  I was looking for inexpensive option for difference frequency waveforms.  I ended up with a signal generator.