I'm repairing a (music) keyboard because the 100 KB sliders are shot. What does the "B" mean? It's a 100 k ohm pot. Does anyone know where I could buy such a thing? It looks to have a strip of resistant paint and I was wondering if I could repair mine with the stuff. Does anyone sell resistive paint? Anyway, I'm going to go google, but I thought I'd check here first.
rK
The delightful thing is that if it's a slide fader made in Japan or Asia generally, B means linear and if it's European, B means 'log' or audio taper.
Fun isn't it ?
What's its function ?
Electronics hobby shop ? Or electronics distributor.
You don't say where you are of course, so I can't suggest a possible but unfortunately both faders and opts generally are often customised to suit the manufacturer and exact replacemnents are often very difficult to find.
No. Forget it. It wouldn't last long anyway.
No. Not in the quantities you need anyway.
Graham
It's a fader on the synthesizer section. There're four octaves 16', 8'
4' and 2' and a white noise generator. The keyboard itself is really cool; it's all analog so the adjustments are all made with faders, switches, and turnpots. Inside, ther are 49 clusters of components corresponding to the 49 keys. Each key has its own sine wave generator (I guess). You can get pretty cool sounds out of it but you can't 'save' anything. The closest you can get is a template they give you in the owner's manual. They tell you to copy it and write in any interesting timbres that you might want to remember. It is ca. 1980.I live in Felton, CA. I was thinking: instead of resistant paint, is there something like a blank PCB but with resistant instead of conductant? I could etch it and cut it myself then. In the mean time, I'm looking for linear slide pots that will fit. I think I'm going to have to build it myself though...
rK
If its audio, it has 10% resistance at 50% travel, so set it in the middle and measure from the wiper to both ends. I'll assume one half wont work... If the other half reads 50K, its linear. If it reads 10K or 90K, it audio.
Just out of curiosity, what is the make and model?
Best regards,
Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis
Make and model of the fader or the synthesizer? (I'm betting on a polymoog?)
korg delta ca. 1979 to 1984
rK
Just post a link to a photo of the sliders against some size reference... there's a bunch of misc sliders at Skycraft... did we determine if they were linear or audio?
It's linear. But now I have another problem: The attack slider works but is a little scratchy, so I'd like to replace it now that I've got it pulled off the board. It is designated as "2MA" Nothing I can find has such high resistance. I don't know why they would design it this way.
BTW, It's a lesson I learned that the resistance of a component is best measured when disconnected from the circuit. Is this correct?
rK
Measure the resistance! If its 100k, a 20k or a 1meg might work just fine if it is being used a a voltage divider. The value isnt the most important feature in that case.
Of course, like everything else, it depends.
You're right, as a voltage divider it doesn't matter in itself what the value of the pot is, since putting the slider at the halfway point will mean the slider contact is at half the voltage across the pot.
But the value may matter a lot, depending on the circuit it is in. If the previous circuit is expecting a high value load on it (admittedly less likely these days when that driver is likely an op-amp and doesn't care), then a lower value pot may load that output too much.
Michael
Just a guess, without seeing the circuit, but since it's controlling attack they probably use it directly in conjunction with a cap. In fact, I would expect they may even be using it as a variable resistance rather than a voltage divider. The R and C together provide the time constant of the attack; by using a bigger R they can use a smaller (cheaper) C.
Yes. Often you can deduce quite a lot from in-circuit measurements, but out-of-circuit is the "gold standard", especially if it is a circuit you are not thoroughly familiar with.
Best regards,
Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis
I think it probably means 2 Megohms, A taper (logarithmic).
Graham
Sorry, but is is not very helpful. Is it possible at all for you to post a picture somewhere? Either on your ISP's "personal webspace" (every ISP I've had has provide a personal page of maybe 10 MB.) or one of those free photo hosts.
And also, for some reason I don't trust those numbers - they could be house numbers and I don't know if _anybody_ has ever heard of a 2M slider. Would you ohm them out? Or are they blown already? Is the company still in business? Could you ask them for a parts list, or even order replacements? Is there a Sams PhotoFact for it?
Yes; there are always sneak paths somewhere when it's in-circuit. Of course, you know to NEVER EVER use an ohmmeter on an energized circuit. Voltmeters are fine, of course - that's how we troubleshoot stuff. :-)
Cheers! Rich
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