Discussion about the Korg PolySix synthesizer

Hi Folks,

Some of you may know that I've replaced the keybed on my Polysix. The new keybed has a long metal cross-bar that sits a little lower than the one on the stock keybed. The new keybed is running into the tall 0.047uF Mylar caps that are standing tall from the KLM-366. Specifically, I'm talking about C31-C36 that are the caps that hold up the sample-and-hold output from IC29.

Being too tall, I'm thinking about replacing them. They're listed as 50V Mylar caps. Would it be OK to replace them with 50V ceramics instead? The ceramics are WAY smaller and would allow my new keybed to fit easily.

The signals being held by these caps is only used for the keyboard tracking of the VCF, so it's not like I need a cap with ultimate fidelity. I think that I need a cap that holds its DC value very well (which is the point of the S-H).

Would a ceramic be OK here?

Chip

According to Analog.com
http://www.analog.com/library/analogDialogue/Anniversary/21.html, you should
be using any of the "poly" (polystyrene, polypropylene, Teflon) types for a
sample and hold circuit, since a ceramic cap has considerable dielectric
absorption which can cause a type of charge memory that can cause errors in
hold level. Some polystyrene caps can be rather tall, so you would have to
choose carefully. The old mylars look like they are about 10mm high. The
caps I'm using on the clone boards are about 8mm, so there is not much
difference. How much clearance do you need for the new keybed? If the old
caps weren't soldered so close to the board, you could just bend them over
so they would lie flatter.



Don B.



_____

From: PolySix@yahoogroups.com [mailto:PolySix@yahoogroups.com] On Behalf Of
chipaudette
Sent: Friday, May 03, 2013 12:05 PM
To: PolySix@yahoogroups.com
Subject: [PolySix] Mylar caps on the sample-hold circuits on KLM-367





Hi Folks,

Some of you may know that I've replaced the keybed on my Polysix. The new
keybed has a long metal cross-bar that sits a little lower than the one on
the stock keybed. The new keybed is running into the tall 0.047uF Mylar caps
that are standing tall from the KLM-366. Specifically, I'm talking about
C31-C36 that are the caps that hold up the sample-and-hold output from IC29.


Being too tall, I'm thinking about replacing them. They're listed as 50V
Mylar caps. Would it be OK to replace them with 50V ceramics instead? The
ceramics are WAY smaller and would allow my new keybed to fit easily.

The signals being held by these caps is only used for the keyboard tracking
of the VCF, so it's not like I need a cap with ultimate fidelity. I think
that I need a cap that holds its DC value very well (which is the point of
the S-H).

Would a ceramic be OK here?

Chip





[Non-text portions of this message have been removed]

no, don't use ceramic. Why don't you move the existing ones to the other
side of the board?

Just a thought

MH

On 4/05/2013 8:51 a.m., backshall1 wrote:
>
> According to Analog.com
> http://www.analog.com/library/analogDialogue/Anniversary/21.html, you
> should
> be using any of the "poly" (polystyrene, polypropylene, Teflon) types
> for a
> sample and hold circuit, since a ceramic cap has considerable dielectric
> absorption which can cause a type of charge memory that can cause
> errors in
> hold level. Some polystyrene caps can be rather tall, so you would have to
> choose carefully. The old mylars look like they are about 10mm high. The
> caps I'm using on the clone boards are about 8mm, so there is not much
> difference. How much clearance do you need for the new keybed? If the old
> caps weren't soldered so close to the board, you could just bend them over
> so they would lie flatter.
>
> Don B.
>
> _____
>
> From: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
> [mailto:PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>] On
> Behalf Of
> chipaudette
> Sent: Friday, May 03, 2013 12:05 PM
> To: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
> Subject: [PolySix] Mylar caps on the sample-hold circuits on KLM-367
>
> Hi Folks,
>
> Some of you may know that I've replaced the keybed on my Polysix. The new
> keybed has a long metal cross-bar that sits a little lower than the one on
> the stock keybed. The new keybed is running into the tall 0.047uF
> Mylar caps
> that are standing tall from the KLM-366. Specifically, I'm talking about
> C31-C36 that are the caps that hold up the sample-and-hold output from
> IC29.
>
> Being too tall, I'm thinking about replacing them. They're listed as 50V
> Mylar caps. Would it be OK to replace them with 50V ceramics instead? The
> ceramics are WAY smaller and would allow my new keybed to fit easily.
>
> The signals being held by these caps is only used for the keyboard
> tracking
> of the VCF, so it's not like I need a cap with ultimate fidelity. I think
> that I need a cap that holds its DC value very well (which is the point of
> the S-H).
>
> Would a ceramic be OK here?
>
> Chip
>
> [Non-text portions of this message have been removed]
>
>

--
Kind Regards<br>
Murray<br>
murray@paintingwithsound.co.nz<br>
www.paintingwithsound.co.nz<br>



[Non-text portions of this message have been removed]

Whoa. Other side of the board? There's a cool idea!

Chip

--- In PolySix@yahoogroups.com, Murray <murray@...> wrote:
>
> no, don't use ceramic. Why don't you move the existing ones to the other
> side of the board?
>
> Just a thought
>
> MH
>
> On 4/05/2013 8:51 a.m., backshall1 wrote:
> >
> > According to Analog.com
> > http://www.analog.com/library/analogDialogue/Anniversary/21.html, you
> > should
> > be using any of the "poly" (polystyrene, polypropylene, Teflon) types
> > for a
> > sample and hold circuit, since a ceramic cap has considerable dielectric
> > absorption which can cause a type of charge memory that can cause
> > errors in
> > hold level. Some polystyrene caps can be rather tall, so you would have to
> > choose carefully. The old mylars look like they are about 10mm high. The
> > caps I'm using on the clone boards are about 8mm, so there is not much
> > difference. How much clearance do you need for the new keybed? If the old
> > caps weren't soldered so close to the board, you could just bend them over
> > so they would lie flatter.
> >
> > Don B.
> >
> > _____
> >
> > From: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
> > [mailto:PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>] On
> > Behalf Of
> > chipaudette
> > Sent: Friday, May 03, 2013 12:05 PM
> > To: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
> > Subject: [PolySix] Mylar caps on the sample-hold circuits on KLM-367
> >
> > Hi Folks,
> >
> > Some of you may know that I've replaced the keybed on my Polysix. The new
> > keybed has a long metal cross-bar that sits a little lower than the one on
> > the stock keybed. The new keybed is running into the tall 0.047uF
> > Mylar caps
> > that are standing tall from the KLM-366. Specifically, I'm talking about
> > C31-C36 that are the caps that hold up the sample-and-hold output from
> > IC29.
> >
> > Being too tall, I'm thinking about replacing them. They're listed as 50V
> > Mylar caps. Would it be OK to replace them with 50V ceramics instead? The
> > ceramics are WAY smaller and would allow my new keybed to fit easily.
> >
> > The signals being held by these caps is only used for the keyboard
> > tracking
> > of the VCF, so it's not like I need a cap with ultimate fidelity. I think
> > that I need a cap that holds its DC value very well (which is the point of
> > the S-H).
> >
> > Would a ceramic be OK here?
> >
> > Chip
> >
> > [Non-text portions of this message have been removed]
> >
> >
>
> --
> Kind Regards<br>
> Murray<br>
> murray@...<br>
> www.paintingwithsound.co.nz<br>
>
>
>
> [Non-text portions of this message have been removed]
>

It turns out that there's not enough space under the board for these tall Mylar caps. But, once I got access to the underside of the board, I saw that the caps did have a little extra length on their legs on the bottom side of the board that I could loosen them up with my soldering iron, push them so that they stand a bit taller, and then simply bend them over so that they are out of the way.

Now they lay a bit flatter, which is just enough to let my new keybed sit down at the height that it's supposed to. Yay!

Pics coming a bit later...

Chip

--- In PolySix@yahoogroups.com, "chipaudette" <chipaudette@...> wrote:
>
> Whoa. Other side of the board? There's a cool idea!
>
> Chip
>
> --- In PolySix@yahoogroups.com, Murray <murray@> wrote:
> >
> > no, don't use ceramic. Why don't you move the existing ones to the other
> > side of the board?
> >
> > Just a thought
> >
> > MH
> >
> > On 4/05/2013 8:51 a.m., backshall1 wrote:
> > >
> > > According to Analog.com
> > > http://www.analog.com/library/analogDialogue/Anniversary/21.html, you
> > > should
> > > be using any of the "poly" (polystyrene, polypropylene, Teflon) types
> > > for a
> > > sample and hold circuit, since a ceramic cap has considerable dielectric
> > > absorption which can cause a type of charge memory that can cause
> > > errors in
> > > hold level. Some polystyrene caps can be rather tall, so you would have to
> > > choose carefully. The old mylars look like they are about 10mm high. The
> > > caps I'm using on the clone boards are about 8mm, so there is not much
> > > difference. How much clearance do you need for the new keybed? If the old
> > > caps weren't soldered so close to the board, you could just bend them over
> > > so they would lie flatter.
> > >
> > > Don B.
> > >
> > > _____
> > >
> > > From: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
> > > [mailto:PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>] On
> > > Behalf Of
> > > chipaudette
> > > Sent: Friday, May 03, 2013 12:05 PM
> > > To: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
> > > Subject: [PolySix] Mylar caps on the sample-hold circuits on KLM-367
> > >
> > > Hi Folks,
> > >
> > > Some of you may know that I've replaced the keybed on my Polysix. The new
> > > keybed has a long metal cross-bar that sits a little lower than the one on
> > > the stock keybed. The new keybed is running into the tall 0.047uF
> > > Mylar caps
> > > that are standing tall from the KLM-366. Specifically, I'm talking about
> > > C31-C36 that are the caps that hold up the sample-and-hold output from
> > > IC29.
> > >
> > > Being too tall, I'm thinking about replacing them. They're listed as 50V
> > > Mylar caps. Would it be OK to replace them with 50V ceramics instead? The
> > > ceramics are WAY smaller and would allow my new keybed to fit easily.
> > >
> > > The signals being held by these caps is only used for the keyboard
> > > tracking
> > > of the VCF, so it's not like I need a cap with ultimate fidelity. I think
> > > that I need a cap that holds its DC value very well (which is the point of
> > > the S-H).
> > >
> > > Would a ceramic be OK here?
> > >
> > > Chip
> > >
> > > [Non-text portions of this message have been removed]
> > >
> > >
> >
> > --
> > Kind Regards<br>
> > Murray<br>
> > murray@<br>
> > www.paintingwithsound.co.nz<br>
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>

If you're interested, here are some pics of how bending over the caps solved my problem...

http://synthhacker.blogspot.com/2013/05/polysix-bending-over-capacitors.html

Chip

--- In PolySix@yahoogroups.com, "chipaudette" <chipaudette@...> wrote:
>
> It turns out that there's not enough space under the board for these tall Mylar caps. But, once I got access to the underside of the board, I saw that the caps did have a little extra length on their legs on the bottom side of the board that I could loosen them up with my soldering iron, push them so that they stand a bit taller, and then simply bend them over so that they are out of the way.
>
> Now they lay a bit flatter, which is just enough to let my new keybed sit down at the height that it's supposed to. Yay!
>
> Pics coming a bit later...
>
> Chip
>
>
> --- In PolySix@yahoogroups.com, "chipaudette" <chipaudette@> wrote:
> >
> > Whoa. Other side of the board? There's a cool idea!
> >
> > Chip
> >
> > --- In PolySix@yahoogroups.com, Murray <murray@> wrote:
> > >
> > > no, don't use ceramic. Why don't you move the existing ones to the other
> > > side of the board?
> > >
> > > Just a thought
> > >
> > > MH
> > >
> > > On 4/05/2013 8:51 a.m., backshall1 wrote:
> > > >
> > > > According to Analog.com
> > > > http://www.analog.com/library/analogDialogue/Anniversary/21.html, you
> > > > should
> > > > be using any of the "poly" (polystyrene, polypropylene, Teflon) types
> > > > for a
> > > > sample and hold circuit, since a ceramic cap has considerable dielectric
> > > > absorption which can cause a type of charge memory that can cause
> > > > errors in
> > > > hold level. Some polystyrene caps can be rather tall, so you would have to
> > > > choose carefully. The old mylars look like they are about 10mm high. The
> > > > caps I'm using on the clone boards are about 8mm, so there is not much
> > > > difference. How much clearance do you need for the new keybed? If the old
> > > > caps weren't soldered so close to the board, you could just bend them over
> > > > so they would lie flatter.
> > > >
> > > > Don B.
> > > >
> > > > _____
> > > >
> > > > From: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
> > > > [mailto:PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>] On
> > > > Behalf Of
> > > > chipaudette
> > > > Sent: Friday, May 03, 2013 12:05 PM
> > > > To: PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
> > > > Subject: [PolySix] Mylar caps on the sample-hold circuits on KLM-367
> > > >
> > > > Hi Folks,
> > > >
> > > > Some of you may know that I've replaced the keybed on my Polysix. The new
> > > > keybed has a long metal cross-bar that sits a little lower than the one on
> > > > the stock keybed. The new keybed is running into the tall 0.047uF
> > > > Mylar caps
> > > > that are standing tall from the KLM-366. Specifically, I'm talking about
> > > > C31-C36 that are the caps that hold up the sample-and-hold output from
> > > > IC29.
> > > >
> > > > Being too tall, I'm thinking about replacing them. They're listed as 50V
> > > > Mylar caps. Would it be OK to replace them with 50V ceramics instead? The
> > > > ceramics are WAY smaller and would allow my new keybed to fit easily.
> > > >
> > > > The signals being held by these caps is only used for the keyboard
> > > > tracking
> > > > of the VCF, so it's not like I need a cap with ultimate fidelity. I think
> > > > that I need a cap that holds its DC value very well (which is the point of
> > > > the S-H).
> > > >
> > > > Would a ceramic be OK here?
> > > >
> > > > Chip
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > > >
> > >
> > > --
> > > Kind Regards<br>
> > > Murray<br>
> > > murray@<br>
> > > www.paintingwithsound.co.nz<br>
> > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
>