Converting low resistance pot to high resistance ?

On Sun, 17 Dec 2006 17:59:35 +0000, N Cook Has Frothed:

No.

How can you make a 100k pot when youve got a variable R that only covers 20k. The answer is you cant. But there are 2.5 buts:

1. if its a ganged pot its poss to put the 2 tracks in series, doubling R. But you cant then have a tapoff that moves anywhere along that track length. However in many apps its ok to use a 2 terminal variable R, so this will sometimes do.
2. You may be able to cut the track width down to increase R. Lot of hassle though!
3. Some ccts can be tweaked so they run happily with a lower value pot.

But in these days of material overflow, its hard to think of any reason to do any of the above now.

NT

Likewise, no.

Arfa

or lots of cuts across the track 2/3 of the way on alternate sides will convert a straight track into a wiggly hence longer and higher R one. All depends if youre in a shop or holed up in pow camp.

NT

Not with only passive components.

--- sam | Sci.Electronics.Repair FAQ:

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Add 4 off 20K fixed resistors in series, with a shorting switch across each (or a rotary selector switch). You should get "steps" of 20K with a 20K range adjustment in each step (i.e. 100K variable down to 80K; 80K variable down to 60K: 60K variable down to 40K: 40K variable down to 20K & 210K variable down to 0).

DOH!

Should of course be:

i.e. 100K variable down to 80K; 80K variable down to 60K: 60K variable down to 40K: 40K variable down to 20K & 20K variable down to 0.

that sounds like a challenge if ever I heard one :)

Take a 100k resistor, scrape the paint off one side. Cut a hole in the track to fit it in, glue it there, and connect the leads to the ends of the track. Paint over the remaining track. Now, if its all set up right, the 100k R acts as the new track.

For more, google foxhole.

NT

Not quite what I had in mind. :)

--- sam | Sci.Electronics.Repair FAQ:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

Hi...

OK, another way to do it, then.

Dis-assemble the control. Attach your meter across the outside contacts. With a piece of fine sandpaper start sanding away at the track. Stop when the meter says 100k. It may or may not be linear, dependent on your sanding abilities.

Take care.

Ken

:)

NT