Hameg scopes how to remove voltage (Y) knobs ?

[elettroluis]

Hi there

I'm cleaning a Hameg 203-6 I got today, I lubricated the switches and rotary controls, all is working fine now and it got rid of the noise but I encountered a strange problem with the two Y (voltage) knobs.

Both, and one especially, are a little hard to turn because they are grinding against the frontal plastic panel.

I confirmed this by pressing with a thumb on the  panel immediately near the rotary switch and turning the knob. It works perfectly.
Releasing the pressure makes the knob rub against the plastic.

So my questions are ... how can the knobs be removed ? Considering there is the vernier knob too which should be removed first I suppose.

And second... it may be possible to reinstall the knobs just a little shy from the plastic surface to avoid the rubbing ?

If that's not possible, maybe I could simply use a light sandpaper on the knob's base to remove 1/10 of millimeter to solve the problem.

I tried to look  for a video where someone is repairing/taking apart an Hameg hoping to actually see how it's done with no success, I'm afraid of pulling and destroy something.

Thanks!

[Chris56000]

Hi!

On older Hameg Oscilloscopes, the variable knobs in the centre of the Y volt/div and TB time/div switches are collet knobs, fixed by a clamp arrangement!

If you run a fingernail gently around the edge of the inner knobs, you'll find the little red or green caps will lift out of the knobs, revealing a Philips screw you then slacken anti-clockwise to release the inner variable knob, which will allow the outer knob to be removed - it just pushes on.

Chris Williams

[elettroluis]

Doh !

Nice to know !

Thank you Chris, I'll try it tomorrow

[elettroluis]

I was able to re-positioning  the knobs a couple of mm. from the panel and now they turn smoothly.

Under the variable knob there is a white plastic disc, and below that there is a nut keeping the Volt/div. knob in place.

In case someone else will have the same question in the future, here are some pictures.