Those caps aren't DC bypass at all. They're functioning as a resistance capacitance time constant. The discharge speed of the cap value is what gives you your velocity intensity; the quicker you hit the key, the more charge that is transferred to the multiplexer. DON"T CHANGE THE VALUE!!
There's an argument that Tantalum has a very poor charge and discharge consistency... that's why he suggests Polystyrene. Also, polystyrene has a longer life expectancy. If you're a purist like me, and you think that the tantalum idiosyncrasies were what the designers intended, replace them with tantalum. Otherwise, Polystyrene would probably give you a more uniform attack throughout the keyboard.
The guy that posted those videos is doing an excellent job and knows his stuff.
Just for your info, tantalum caps are way more reliable now than the ones from the 70's.
Please don't mess with these things if you don't know what you are doing.
--- In yamahacs80@yahoogroups.com, "Leslie Schwartz" <lhs_emf@...> wrote:
>
> Dave,
>
> I appreciate the information and this is not a challenge, just an attempt to
> follow up.
>
> The fact that the tantalum was intended for DC bypass, appears not to
> require a polarized cap? Again, it was my expectation that a polar cap would
> be preferable in this application?
>
> And of course all caps can eventually leak, and modern electrolytics appear
> to have a better reputation for longevity and size to capacitance rations
> than they did 25 years ago.
>
> And as to sizing and precision of the capacitance spec, again I would think
> the more capacitance the better in this application?
>
> And comments and information is appreciated.
>
> -----Original Message-----
> From: yamahacs80@yahoogroups.com [mailto:yamahacs80@yahoogroups.com] On
> Behalf Of David Rogoff
> Sent: Sunday, February 20, 2011 11:48 AM
> To: yamahacs80@yahoogroups.com
> Subject: Re: [yamahacs80] RE: Re: My own CS-80
>
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> >
> > Leslie Schwartz <mailto:lhs_emf@...>
> > February 20, 2011 8:55 AM
> >
> >
> >
> > I agree that the recommendation is puzzling to me too. I would have
> > expected
> > that new polarized electrolytics would have been the type to use for a
> > replacement of the tantalums.
> >
> > Good video though, and some more good info on CS-80 maintenance/repairs.
> > Thanks.
> >
> > -----Original Message-----
> > From: yamahacs80@yahoogroups.com [mailto:yamahacs80@yahoogroups.com] On
> > Behalf Of Quazimodo
> > Sent: Sunday, February 20, 2011 10:31 AM
> > To: yamahacs80@yahoogroups.com
> > Subject: [yamahacs80] Re: My own CS-80
> >
> > I think the YouTube series of videos on saving the CS80 - by Gavin
> > Curtis -
> > shows those tantalum capacitors replaced with non-polarised polystyrene
> > caps.... can that be right, replacing polarized with non-polarized?
> > ------------------------------------------------------------------------
> I haven't seen the videos, but a couple of general capacitor notes.
> First, pretty much no one has used tantalums in many years now. They
> were a way to get a high value in a very small package. However, they
> turned out to be really flaky, especially if ever connected backwards.
> There are much better replacements now. Also, there's nothing wrong
> with using a non-polarized cap to replace a polarized one. Again,
> polarized (e.g. tantalums - which can blow up, electrolytics - which dry
> out and fail over the years) caps were a way to get a higher value in a
> smaller package if you knew the voltage only would go one way - like in
> a power supply.
>
> I'll have to look into the polystyrene caps more, but if they have the
> same capacitance value, voltage rating, and they're small enough
> physically, they're probably a much better choice. They shouldn't dry
> out like electrolytics. Non-polarized means you don't have to worry
> about putting it in backwards. And, I'm sure they better in other ways
> - better tolerance, lower ESR, etc that could make them perform better
> in some applications.
>
> David
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
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