Re: Alto L12 mixer, only 2007

Dave M <masondg4xx4@xxxxxxxxxxxxx> wrote in message
news:g5p4n4h5e4ru0p5jg9sqafe6ugcugjrnrq@xxxxxxxxxx
On Fri, 16 Jan 2009 17:27:46 -0000, "N_Cook" <diverse@xxxxxxxxx> wrote:

And the master slider pot has failed (Chinese so assume unavailable).
Long but tiny cross section stereo 2x 10K log pot. Found a larger one
that
there maybe enough space and can be screwed onto/under/through the top
panel
and wired into the pcb but it is 2x 250K lin of course.
10K and 1K resitors in parallel with each pot, will that be a work around
or
will the characteristic be too "lumpy" on the low end?


You might look at some of the suggestions at
http://www.geofex.com/article_folders/potsecrets/potscret.htm and see if
any of
them might offer a workable solution for you. I realize it will probably
never
be an exact match for the original taper, but sometimes it can be worked
out
really close.
Good luck
==============

Dave M

Never take a laxative and a sleeping pill at the same time!!


" * I have heard that you can use copier toner dust to melt over a
section of worn resistor material and repair it. "

probably referring to my tip for worn pots, fully detailed here

Dismantle the pot down to the carbon track clean/degrease.
Make up resistive compound from photocopier toner and graphite powder
obtainable from locksmiths for dry "lubrication".
the following resistivity values are very approximate for .02 inch thick
film.
graphite:toner ratios
1:1 ,200 ohm per square inch
1:10, 100k ohm per square inch
1:30 10M ohm per square inch
Mask off area surrounding carbon track,sprinkle on the powder,fuse the film
in a low oven approx 150 degrees centigrade or hold the barrel of a
soldering
iron 1mm from the powder to heat .When fused lightly abraid with a
nail file,and reassemble pot.High ohmic pots are a bit iffy,low ohmic are
fine.
p.s. I would be interested to hear of any suggestions for higher resistivity
addmixture for higher ohmic pots (for more even distribution)


Which I will probably use for this Chinese pot. the main problem with it is
not having a nice flat surface after "curing". Needs some sort of aqua
process perhaps to give an initial flat surface.
Aquadag or whatever EFI/EMI screening black (dries to slightly brown side of
black) stuff is , may be useful for very low ohm but probably too brittle
and does not adhere to impervious surfaces.
My can of it is too old to get product details RS stock number "551-570"
other than it contains MEK and xylene

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


.

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