100KB sliders

R

rabiticide

Guest
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
 
rabiticide wrote:

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.
Click to expand...
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 ?


Does anyone know where I
could buy such a thing?
Click to expand...
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.



It looks to have a strip of resistant paint
and I was wondering if I could repair mine with the stuff.
Click to expand...
No. Forget it. It wouldn't last long anyway.


Does anyone sell resistive paint?
Click to expand...
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.
 
On Sat, 15 Mar 2008 13:02:47 -0700 (PDT), rabiticide
<rabiticide@gmail.com> wrote:

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...
Click to expand...

Just out of curiosity, what is the make and model?

Best regards,


Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!
 
Make and model of the fader or the synthesizer? (I'm betting on a
polymoog?)
 
On 3ÔÂ15ČŐ, ĎÂÎç3Ęą05ˇÖ, rabiticide <rabitic...@gmail.com> wrote:
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
Click to expand...


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On Mar 16, 7:32 am, NoS...@daqarta.com (Bob Masta) wrote:
On Sat, 15 Mar 2008 13:02:47 -0700 (PDT), rabiticide



rabitic...@gmail.com> wrote:
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...

Just out of curiosity, what is the make and model?

Best regards,

Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!
Click to expand...
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?
 
On Mar 23, 6:00 am, BobG <bobgard...@aol.com> wrote:
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?
Click to expand...
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.
 
BobG (bobgardner@aol.com) writes:
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.
Click to expand...
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
 
On Tue, 25 Mar 2008 11:53:30 -0700 (PDT), rabiticide
<rabiticide@gmail.com> wrote:

On Mar 23, 6:00 am, BobG <bobgard...@aol.com> wrote:
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.
Click to expand...
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.

BTW, It's a lesson I learned that the resistance of a component is
best measured when disconnected from the circuit. Is this correct?
Click to expand...
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
www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!
 
It's linear. But now I have another problem: The attacksliderworks
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.

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.
Click to expand...
Okay - that rings some dusty bells... I am lucky enough to have the
circuit diagram. I really appreciate your help on this. I posted the
diagram on my blog at:

http://rabbitshead.blogspot.com

You can see four dashed-line boxes around four resistors with the
little arrows through them. These controls comprise the envelope
generator:

A = Attack
D = Delay
S = Sustain
R = Release

Like I said, the 2MA attack pot is flaky and I would like to replace
it. But I've searched high and low and can find, at most, a 1MA
slider. Will this work?

rK
 
On Sat, 29 Mar 2008 23:40:25 -0700 (PDT), rabiticide
<rabiticide@gmail.com> wrote:

It's linear. But now I have another problem: The attacksliderworks
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.

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.

Okay - that rings some dusty bells... I am lucky enough to have the
circuit diagram. I really appreciate your help on this. I posted the
diagram on my blog at:

http://rabbitshead.blogspot.com

You can see four dashed-line boxes around four resistors with the
little arrows through them. These controls comprise the envelope
generator:

A = Attack
D = Delay
S = Sustain
R = Release

Like I said, the 2MA attack pot is flaky and I would like to replace
it. But I've searched high and low and can find, at most, a 1MA
slider. Will this work?
Click to expand...
First of all, I assume that "MA" is Korg-speak for "Megohm".
(Normally just abbreviated "M".) Whatever, if your replacement pots
are half the value of the originals, all the time constants will be
halved as well (envelopes speeded up x2) for the same relative
settings. If you rarely use the half of the sliders that give the
longest envelopes, you might be happy with a simple replacement.
However, if you want to restore the original range, you can also
replace capacitor C6 with one of twice its value. Note that this is
an electrolytic, so be sure to observe polarities.

Best regards,


Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!
 
Bob Masta wrote:

First of all, I assume that "MA" is Korg-speak for "Megohm".
(Normally just abbreviated "M".)
Click to expand...
I think it probably means 2 Megohms, A taper (logarithmic).

Graham
 
rabiticide wrote:

It's linear. But now I have another problem: The attacksliderworks
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.

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.

Okay - that rings some dusty bells... I am lucky enough to have the
circuit diagram. I really appreciate your help on this. I posted the
diagram on my blog at:

http://rabbitshead.blogspot.com

You can see four dashed-line boxes around four resistors with the
little arrows through them. These controls comprise the envelope
generator:

A = Attack
D = Delay
S = Sustain
R = Release

Like I said, the 2MA attack pot is flaky and I would like to replace
it. But I've searched high and low and can find, at most, a 1MA
slider. Will this work?
Click to expand...
It will certainly work but you will get reduced range of the control
Possibly this won't matter too much and it's crtainly an improvement over a
flaky control.

Graham
 
I've tried lots of Home Remedies to cure scratchy tube guitar amp
pots.. I've heard WD40.... others say nooooo... thats a solvent and
will eat the conductive plastic... How about Amway or some similar
silicon slippery stuff (wow 5 Ss in a row)? Just need to knock the
dust off the wiper area.
 
BobG wrote:

I've tried lots of Home Remedies to cure scratchy tube guitar amp
pots.. I've heard WD40.... others say nooooo... thats a solvent and
will eat the conductive plastic... How about Amway or some similar
silicon slippery stuff (wow 5 Ss in a row)? Just need to knock the
dust off the wiper area.
Click to expand...
When they're badly worn the carbon track is worn away. No solvents going
to help that.

Graham
 
On Sun, 30 Mar 2008 11:50:13 -0700 (PDT), BobG <bobgardner@aol.com>
wrote:

I've tried lots of Home Remedies to cure scratchy tube guitar amp
pots.. I've heard WD40.... others say nooooo... thats a solvent and
will eat the conductive plastic... How about Amway or some similar
silicon slippery stuff (wow 5 Ss in a row)? Just need to knock the
dust off the wiper area.
Click to expand...
if it's only dust, then:

http://www.google.com/search?hl=en&q=contact+cleaner

JF
 
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