D-shaft knobs upside down

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Common Wiggler
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D-shaft knobs upside down

Post by nrrrd » Thu Nov 07, 2019 8:02 am

Yesterday I completed my first DIY module, a NLC Timbre.
The module is great and worked first time!

I thought I'd be clever and match the knobs to the rest of my system, which is mostly Make Noise.

I got the matching knobs from Thonk, and the D-shaft pots required to mount them.

However, the pointer is upside down, i.e. it points towards the bottom of the case, rather than the top, during its sweep.

Is there anything I can do about this or do I have to live with it and chalk it up to experience?

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Post by Just another rookie » Thu Nov 07, 2019 8:10 am

Reverse D shaft knobs might be the answer, if available in the type you require.

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Post by cretaceousear » Thu Nov 07, 2019 8:40 am

Unsolder them from the board - fix them to the panel the right way up - use wire to link them to the board - then you have to figure out a way to mount the board to the panel. All doable but might take a bit of head scratching!
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dot matrix madness
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Post by dot matrix madness » Thu Nov 07, 2019 10:02 am

There are some REAN knobs for D-shaft, which have an insert that can adjusted to the wanted position of the pointer.
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Post by ersatzplanet » Thu Nov 07, 2019 12:09 pm

Pots and knob specs very wildly if you buy from bulk or surplus shops. Companies that make gear have to spec them to match and often the pot makers will make batches to those specs for a company. Overruns and overstock of these end up at big box retailers.

An 18T pot shaft is NOT universal for instance. Pot shafts are spec'd for a couple of parameters:

Shaft overall length is given, the length of the knurl is given, the diameter is given, the orientation of the knurl is spec'd. Knurled shafts are made with the pot mounting orientation in mind. When the pot is turned to its full rotation (almost all pots have 300 degrees of rotation), what is at the "top" of the shaft? Is it to be a "hill" (the pointy bit of a knurl) or is it a "valley" (the bit between the points? They are different if the pot is mounted vertically or horizontally - 10 degrees different. If the knob doesn't match, it will not line up with the graphics. Just look at older Doepfer modules with horizontal vs vertical mounted PCBs. One type has the pots not lining up with the graphics because he used the same knobs for both.

Flatted shafts have the same problems. On a flatted shaft you spec the shaft length, the length of the cutaway, the depth of the cutaway, and the orientation (flat towards the pointer or away). If the flat doesn't match the knob, it will be too far or to close to the panel, and if the flat depth is wrong, the knob will turn a little at the ends of the pot sweep, or won't go on at all.

Some knobs with set screws can be used with both knurled shots or flatted ones if the shaft length and diameter is OK. The set screw has to be log enough to cover the flat depth, and in the right location to work with flatted shafts and the shaft has to be the right diameter in both cases.

Basically the takeaway from all this is to buy a couple of test pieces and see if you can live with the results. We use set screw knobs on both knurled and flatted shafts and the only hassle is to lift them off the panels and bushings so they don't scrape.

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Common Wiggler
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Post by templar » Thu Nov 07, 2019 4:23 pm

If you can desolder - then desolder the pots and replace them T18 shaft. You can get Make Noise knobs in T18 shaft.

Only other non complicated option will be another style of knob.

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Post by GGW » Thu Nov 07, 2019 6:24 pm

Could you consider taking a file to the shafts and putting a new flat surface on the other side? Sometimes for a small job, a bit of work is worth it to solve the problem. I guess it depends on your patience and how many shafts there are.

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Post by nrrrd » Fri Nov 08, 2019 6:45 am

Thanks for the ideas everyone. I've gone for the slightly prosaic method: I've put the module in upside down! :)

I think I'm going to have a go at filing the knobs next (there are only two knobs).
Annoyingly I substituted the pots and knobs at the last minute from round 6.35mm pots and Davis 1900h knobs with a set screw. Which would have just worked. :doh:

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