Question on pots

[famous beagle]

Hi,

I recently bought a Rane PE 15 parametric EQ, and one of the level pots has a broken shaft, so I need to get a new one. I got the schematic and have identified the pot on it as R35. On the schematic it says 100KW for that pot. I assume that's 100K, but what's the "W" for?

Thanks!
Chad

 

[Steenamaroo]

The W is telling you about the pot taper.
As far as I know it'll be log + antilog either side of the mid point.
At very least the response is symmetrical.

I think you'd see it more often on a tone control that as zero as the midpoint, for example.

Anyway, just google 100kw or w100k potentiometer. You'll find plenty.

 

[famous beagle]

The W is telling you about the pot taper.
As far as I know it'll be log + antilog either side of the mid point.
At very least the response is symmetrical.

I think you'd see it more often on a tone control that as zero as the midpoint, for example.

Anyway, just google 100kw or w100k potentiometer. You'll find plenty.

Awesome, thanks for the info. Looking inside the unit, I found that the pot is unlike any I've ever seen. Granted, I'm not a tech, so I haven't seen a lot of pots, but I've been inside a good deal of guitars and amps, and I haven't seen something that looks exactly like this before.

See the attached images. Most pots I see look like the "100K pot" image (attached), with the brown board at the bottom of the shaft, and the enclosed housing beneath that.

But the pots in the Rane have the housing first, and the brown board beneath that.

I'm sure this is commonplace for techs, but I've never seen it before.

Anyone know what's going on?

Thanks!

 

[ecc83]

That pot has a tapped track. Mechanically centre tapped but electrically, WTF knows!

Assuming it still works you need to centre the wiper mechanically then measure the resistances from wiper to each end of track and ends of track to tap.

You are probably only going to get the right pot from the OEM or, by finding all the markings on the pot and then seeking out the manufacturer.

Getting the pot out without damaging the print track will be tricky, don't want to school Granny so shout if you need an MO!

Dave.

 

[Steenamaroo]

It's just centre tapped. Here.
This ^ doesn't match the spec you need but it shows that they exist, at least!

Dave. Why does he need to measure it?

 

[ecc83]

"Dave. Why does he need to measure it? "

Well, if he can get an exact replacement then of course he doesn't but if not measurement will tell him the law.
Actually, looking at the map I would bet it is linear and the tap is at electrical centre.

Dave.

 

[Steenamaroo]

Thanks for the reply, Dave. So the specific taper is in question? The W just denotes symmetry then?

I was able to find a centre tapped B taper 100k online earlier, but I didn't post a link to it.
Can look it up again if OP is stuck.

 

[famous beagle]

Thanks for the info y'all.

Steen: I've been able to find lots of center tapped pots on line, but all of them are dual (or stereo). I haven't yet seen one like mine.

ecc83: I've contacted Rane to see if they can help me locate the part. They actually had a link on their site for someone that specifically deals with replacement parts, so maybe they'll come through. If not, and if I do end up having to rig something, I might need some help performing the measurements you called for. I know how to use multimeter (for basic things), but you might just have to tell me where to put the leads because I don't know a whole lot about pots yet.

 

[DM60]

Check the part number. Most manufacturers use "Off The Shelf Parts". Designs are normally around this so that fewer custom parts are required. If you can get the part number from the pot, you might be able to order it from various places.

 

[Steenamaroo]

Thanks for the info y'all.

Steen: I've been able to find lots of center tapped pots on line, but all of them are dual (or stereo). I haven't yet seen one like mine.

Ah, right enough - The ones I saw were dual.
If it'll physically fit there's no problem, though. You'd just wire up one set of terminals and ignore the others.

 

[famous beagle]

Check the part number. Most manufacturers use "Off The Shelf Parts". Designs are normally around this so that fewer custom parts are required. If you can get the part number from the pot, you might be able to order it from various places.

Thanks. I've tried that. I got the only markings off of it that I could find (without opening the pot up). It looks as though it's made by the ALPS corporation, so I've contacted them, since searching for the part number online produced no results. It's looking as though I'm going to have to formulate something of my own to make it work.

Or I suppose it may be possible to rig something with some Gorilla glue. The good news is that the knob is for the 20 - 300Hz band, and I still have a 60-1KHz band next to it that can cover the majority of the bass.

 

[ecc83]

"The W just denotes symmetry then?"
Dunno mate! The codes on pots is not standardized across brands. "A" usually means a standard log taper but some firms call it "B"!

OP, will be glad to help wherever I can.

Dave.

 

[DM60]

Thanks. I've tried that. I got the only markings off of it that I could find (without opening the pot up). It looks as though it's made by the ALPS corporation, so I've contacted them, since searching for the part number online produced no results. It's looking as though I'm going to have to formulate something of my own to make it work.

Or I suppose it may be possible to rig something with some Gorilla glue. The good news is that the knob is for the 20 - 300Hz band, and I still have a 60-1KHz band next to it that can cover the majority of the bass.

Sometimes these things are not so obvious to many people. My lawnmower just broke (ball joint to the steering linkage) I did the same thing as you are talking about, but I welded it so it would work. Gorilla glue, welding, whatever to make it work.

 

[famous beagle]

I got a response from Rane that sounds promising. He asked if I need the pot or just the extension. I don't exactly understand what he meant, so I sent him the pictures in hopes that he can tell me.

 

[DM60]

I got a response from Rane that sounds promising. He asked if I need the pot or just the extension. I don't exactly understand what he meant, so I sent him the pictures in hopes that he can tell me.

Sounds to me you got it, you just now have to sort out what you need.

 

[BroKen_H]

I've got friends that think pot taper is the end of the joint...

 

[famous beagle]

Well, it turns out that they don't make the part anymore and haven't for quite a while. After doing some thinking, I decided to try a repair to see what I could come up with. I was already missing one knob, so I planned on replacing all of the knobs anyway. I found a short dowel rod that was almost the same size as the knob shaft, and I was able to chisel a bit off to make it fit into the knob like a glove. I cut off the dowel at the bottom of the knob and drilled a short 1/16th inch hole into the bottom of the dowel.

Then I drilled a similar hole into the plastic shaft. I found a nail that was just about the same diameter (1/16in) and cut off its head to make it the correct length. Then I glued it into the dowel hole and then glued the other end into the shaft hole.

Works like a charm! I was so excited throughout the process that everything was actually working that I forgot to take pictures. And now I can't take it out again unless I want to break the glue, which I don't. Anyway, just thought I would update. DIY feels so good when you get it right.