[sdiy] Korg Delta problem

[Gordonjcp]

On Tue, Jun 19, 2018 at 12:45:31AM +0200, sleepy_dog at gmx.de wrote:
> Gordonjcp wrote:
> >On Mon, Jun 18, 2018 at 10:01:45PM +0200, Jean Bender wrote:
> >>thanks !
> >>you mean the caps from the power supply ? How could the power supply
> >>only disturb or make no functionnal only half part from the synth ?
> >You'll never find "bad caps" in a synth.  They're pretty much a myth.
> >
> How so? Is it a myth that electrolytic caps will chemically degrade?

Yes.  You might see them fail if they've been thoroughly hammered in
cheap badly-designed switchmode power supplies.

> I have been told by more than one EE not to bother using
> electrolytics that have been laying around for 5 years, not just for
> things requiring low ESR, not for anything.

Horseshit.  If you believe that, I've got some lovely speaker cable to
sell you, complete with lithodynamic vibration mass compensators.

> I don't have any numbers. But even in some simple old synth PSU with
> a pair of fat caps and linear regulation, it would be bad if those
> caps got a huge ESR and reduced capacitance, no? Now I can imagine
> that this is considered in the circiut designs, but only so much?

They won't get "huge ESR and reduced capacitance" though.

The electrolyte isn't milk.  It doesn't go off.

There is so much utter bollocks talked about capacitors, it's absolutely
mindblowing.  In 30-odd years I've replaced less than a dozen faulty
electrolytics in (what feels like) thousands of pieces of equipment.

People are obsessed with this idea that every fault is "bad caps".  It's
never a capacitor.  It's always something else, although I'll grant you
in most linear power supplies it's the rectifier diodes which fail and
*then* take out the big electrolytics.

It's got to the point where I won't touch anything that's been
"re-capped".  I just assume that if it's been "re-capped" and it's still
not working, it's now beyond repair.  It was probably a simple fix
before the poke-and-hope brigade got their grubby mitts on it.

-- 
Gordonjcp