[sdiy] ALPS RK09K 9mm "knob shaft" pots

Sun Aug 26 10:45:15 CEST 2012

Here are the results of my search for sources of these compact pots
which need no knobs.  They are available in dual versions, but I am only
looking for single, primarily in a vertical format (shaft is
perpendicular to the PCB), ideally in a 20mm shaft length.

These little pots are only rated for 5,000 rotation cycles, but in my
experience have been spectacularly reliable, as I noted in a recent
message: "Re: [sdiy] Audio taper pots - shunt resistors and contact
resistance".

I guess they would be of interest to some people for DIY-Synth projects.
 Unfortunately, they seem difficult to obtain.  ALPS currently has two
numbering systems for these pots.  One is a "Recommended Products" code
such as:

  RK09K1130A8G

which requires a lookup to see what it means.  The other is a numbering
system which specifies everything, such as:

  RK09K111-K25-C0-B103

I can't find a single document on the ALPS site which specifies these
two systems, but here is an earlier version:

  https://www1.elfa.se/data1/wwwroot/assets/datasheets/RK09K_eng_TDS.pdf

The current list of Recommended Products seems to exist only as a web page:

http://www.alps.com/WebObjects/catalog.woa/E/HTML/Potentiometer/RotaryPotentiometers/RK09K/RK09K_list.html

with a PDF copy.  The "other" system is documented in a PDF which is
linked to from there:

http://www.alps.com/WebObjects/catalog.woa/E/PDF/Potentiometer/InsulatedShaft/RK09K/RK09K_VARIETYOTHER.PDF

There are some values in stock in an Australian distributor in both the
vertical format (shaft perpendicular to PCB) and the horizontal format.
Mouser also has a few values and so does Elfa Electronics.  More details
below.

On 2012-08-26, of the ALPS Recommended Products only 4 of the were knob
type vertical and 2 knob type horizontal.  Of this set, the  only knob
type vertical with a 20mm shaft without centre detent is a 10k B linear:

http://www.alps.com/WebObjects/catalog.woa/E/HTML/Potentiometer/RotaryPotentiometers/RK09K/RK09K1130A5R.html

The photo shows a 30mm shaft version, I think.  The drawing is of the
20mm version.

The above-mentioned PDF shows all the options and how to create a part
number in the "other" scheme.  For single units (not dual pots), with
the shaft perpendicular to the PCB surface (vertical type) the part
numbers are:

  RK09K1130-Kaa-bb-cddd

where the final K is for Knob type, as used in the Devil Fish:
http://www.firstpr.com.au/rwi/dfish/ and where aa is the length of the
shaft measured from the PCB surface.  Most of the models are F for Flat
type shafts.  The Devil Fish pots are 20mm from the surface.  The other
options are 15, 25 and 30mm.

The 0 after the 113 has no specified meaning.  When I ordered these pots
in the past, there was no such 0 in the part numbers.

bb is C0 for no centre detent, or C1 with centre detent.

c is for the resistance taper, with my descriptions, based on the graphs
in this PDF:

  A = 15A  Audio AKA log
  B = 1B   Linear
  C = 15C  Reverse audio AKA reverse log
  V = 3B   Steeper linear with shallow start and end

ddd is:

  502   5k
  103  10k
  203  20k
  503  50k
  104 100k
  204 200k

This explains why the 500k log pots I use in the Devil Fish involved a
special order.  The 10k, 100k and 500k log pots I use would therefore be:

  RK09K1130-K20-C0-A103
  RK09K1130-K20-C0-A104
  RK09K1130-K20-C0-A504

I tried Googling for:

  "RK09K1130-K20"
  "RK09K113-K20"

The second term was more fruitful.

The best distributor I know of for these pots is Switches Plus here in
Melbourne, where I get my pots from.  They publish a stock listing which
is linked to from their main page:

  http://www.switchesplus.com.au/stock/Switches.Plus.Stock.Availability.pdf

This was reasonably up-to-date, being dated 2012-08-03 today (2012-08-26).

Their part numbers don't always conform to the ALPS schemes.  Here are
the relevant lines, from several pages, ignoring duplicates with my
addition of K for knob type (they sometimes refer to these as "knurled")
and F for flatted shaft.  I have also added V for vertical and H for
horizontal (shaft parallel to the PCB).  (This will only look good in a
fixed width font.)

V  K   RK09K113-10KA RK09K113-K20-CO-A103 KNURLED..LM1=20MM      1689
V   F  RK09K113-10KAS FLAT..LM1=20MM POT 9MM                      485
V  K   RK09K113-50KA #ALPS KNURLED..LM1-20MM POT 9MM              162
V  K   RK09K113-50KB #ALPS KNURLED..LM1=20MM POT 9MM              223
V  K   RK09K113-5KA #ALPS KNURLED..LM1=20MM POT 9MM                36

 H K   RK09K111-10KA #ALPS KNURLED..LM1=20MM POT 9MM OHM          332
 H  ?  RK09K1110A7P RK09K111-10KB AKLPS POT L=20MM                297

V  K   RK09K113-100KB ALPS KNURLED..LM1=20MM POT 9MM               56
V   ?  RK09K113-10KB #RoHS RK09K1130A5R ALPS POT L1=20MM          423

 H K   RK09K111-500RB #ALPS KNURLED..LM1=20MM POT 9MM            1093
 H K   RK09K111-5KA #ALPS KNURLED..LM1=20MM POT 9MM               121
 H K   RK09K111K20C0B203 ALPS 20KB POT LM1=20MM                   295

So for the knob type, 20mm, vertical (shaft perpendicular to the PCB),
Switches Plus had in stock:

   5k A log         36

  10k B linear     423 (may not be knob type)
  10k A log       1689

  50k B linear     223
  50k A log        162
 100k B linear      56

For horizontal pots:

 500R B linear    1093

   5k A log        121

  10k B linear     297 (may not be knob type)
  10k A log        332

  20k B linear     295

A Mouser search for "RK09K" produces quite a few listings, mainly for
flatted shaft pots.  All the pictures in these search results show
flatted shafts, but the descriptions and part numbers of some are for
"knob" type or "knurled - serrated" which I assume means the same thing:

http://au.mouser.com/ProductDetail/ALPS/RK09K1130A8G/?qs=sGAEpiMZZMtC25l1F4XBU3JeeCo7XMTlBi0F3pTrQUE%3d

  RK09K1130A8G  10k B linear, vertical shaft 15mmm
  448 in stock Q1 price $0.675

http://au.mouser.com/ProductDetail/ALPS/RK09K111-K25-C0-B103/?qs=sGAEpiMZZMtC25l1F4XBU1HrDNmn%252bs273LSCS9%2fRmNs%3d

  RK09K111-K25-C0-B103  10k B = linear, horizontal, 25mm shaft.
  212 in stock, Q1 price $2.02 (! but comes down at larger quantities) 	

http://au.mouser.com/ProductDetail/ALPS/RK09K1110-K25-C0-B103/?qs=sGAEpiMZZMtC25l1F4XBU7kMr1YZdyFQl3Q4yYU1pd8%3d

  RK09K1110-K25-C0-B103 10k B = linear, horizontal, 25mm shaft
  This appears to be identical to the one above, except for the extra
  zero in the part number.  It has different stock numbers and prices:
  437 in stock, Q1 price $1.71.

http://au.mouser.com/ProductDetail/ALPS/RK09K11100E9/?qs=sGAEpiMZZMtC25l1F4XBU3JeeCo7XMTlEUCEcl9SZLY%3d

  RK09K11100E9 50k 1B linear, with centre detent,
  horizontal, 20mm shaft.
  100 on order, 0 stock. Q1 price: $0.716.

http://au.mouser.com/ProductDetail/ALPS/RK09K1130A70/?qs=sGAEpiMZZMtC25l1F4XBU3JeeCo7XMTl%2fT%252bpshRq2Yk%3d

  RK09K1130A70 10k B linear vertical 30mm shaft.
  250 on order, 0 stock, Q1 price: 0.675.

http://au.mouser.com/ProductDetail/ALPS/RK09K1130081/?qs=sGAEpiMZZMtC25l1F4XBU3JeeCo7XMTlUXyUqIf0koM%3d

  RK09K1130081 10k B linear, vertical 20mm shaft,
  100 on order, 0 stock. Q1 price: $0.716.

The Mouser summary is:

 Vertical:

   15mm  10k B linear         448 in stock    $0.675
   20mm  10k B linear         100 on order    $0.716
   30mm  10k B linear         250 on order    $0.675

 Horizontal:

   20mm  50k B linear detent  100 on order    $0.716
   25mm  10k B linear         212 in stock    $2.02

This is far too slim a selection to get excited about.

Elfa Electronics has some which are, according to the photos, all knob
type.  The prices are around 1.37 Euros or less for Q10.  Here are the
Elfa part numbers and other details.  Elfa do not quote proper ALPS part
numbers.  The pages don't specify the shaft length.  They have total
length in mm, which I have put in brackets besides what I assume is the
shaft length.

  64-352-19 horizontal   10k B linear  20mm?     (23)   stock  21
  64-352-20 horizontal  100k B linear  25mm?     (27)   stock  34
  64-352-21 horizontal  100k A log     20mm?     (22)   stock  15

  64-352-22 vertical     10k B linear  20/25mm?? (25)   stock  51
  64-352-24 vertical     50k B linear  25/30mm?? (30)   stock  36
  64-352-23 vertical    100k B linear  25/30mm?? (30)   stock  45
  64-352-25 vertical     10k A log     25mm?     (29)   stock 124

Newark (element14, Farnell etc.) has RK09K11310KA and RK09K11310KB.  As
far as I can tell, these are neither of the above numbering systems, and
are flatted shaft, 10 log and linear respectively, in vertical packages.
 http://au.element14.com is the same.

RS Components has quite a few matches for RK09K.  Their ALPS part
numbers look like the "Recommended" variety but they don't all match the
current ALPS list.  There is a link to an old circa 1998 ALPS document:

  http://australia.rs-online.com/web/p/potentiometers/2633034/

which has older numbering system, for vertical pots with 280 degree
turning angles:

  RK09K113nnnnn

when nnnnn is an "ALPS control number".  They used to make gray shaft
knob types.

However, the RS part numbers have only four alphanumerics.  So maybe
this is according to yet another ALPS numbering system!  Those which
appear to have knob shafts all seem to be too short.  The printed
catalogue lists a subset of them as having shaft lengths of "17.4mm"
which means 15mm - none seem to be 20mm so I won't investigate further.

These sites return nothing for a search for "RK09K":

  http://www.digikey.com
  http://www.jameco.com
  http://www.rapidonline.com
  http://www.sparkfun.com

I wrote that my technique for painting silver in the slots of the knob
shafts of the ALPS RK09 9mm pots was to use a piece of kynar insulation
from wire-wrap-wire poked into the felt nib of a large silver marker. I
am currently using a Uni-Paint marker "PX-20(L) SILVER":

  http://www.uniball.com/catalog/show/product.php?no=47

I think most people would find it easier, for small quantities of pots,
to use a small custom-cut brush with the ink of a marker such as this.
However, I found I was making mistakes with the brush, and that the
kynar-tube-nib pen was easier to use quickly and reliably.

In addition to the kynar tube, the trick is to have a fine piece of
copper wire, nylon fishing line or nylon single-strand sewing thread (I
can't remember which I used) inside the kynar tube, to help create
capillary action to get the ink to the tip, and to reduce difficulties
with the ink drying.  The big problem is getting ink flowing after the
pen has not been used for a while.  I found it helpful to use ultrasonic
cleaner filled with Shellite (a hydrocarbon like petrol/gasoline).

I do this under a stereo zoom microscope, but I guess that good
magnifying glasses would be sufficient.  With this custom-built pen, it
only takes a few seconds and there are few rejects.  However, if the ink
is too inclined to flow, then there can be many rejects.

With lots of use, these little pots become somewhat grubby and the line
is hard to see.  I don't have a complete solution for this, though
cleaning with soapy water is probably the best approach.

 - Robin