[sdiy] Re: Learning electronics (was Polyevolver)

[harrybissell]

Bob Weigel wrote: <snipp'd and mutilated)

> I wasn't thinking flameproof resistors would be likely all over a moog
> rogue and hence the thought there :-).  Perhaps a couple in the power
> supply.  Some mixing boards use them on each module which is a nice idea
> to effectively fuse each section.

Don't confuse "Flameproof" with "Fusible" resistors.  Flameproof means they
will not light on fire when they fail.  They can deliver SO MUCH wattage that
they may glow cherry red and burn everything else in sight, before they open.

Fusible resistors are designed to open quickly when overloaded.

(I know, a manufacturer I worked for made the mistake and wondered why failed
boards suddently looked like a barbeque !!!)

> btw and are often yellow
> colored.  I can't recall what they use for dielectric in those at the
> moment.

Those are usually multilayer ceramic. Terrible temperature stability, who cares
in a bypass application (ok KD... who cares at audio frequencies anyway :^)

> But small caps like that all have frequency
> response characteristics that are fine for audio and microphonic
> characteristics and field exposure aren't usually a factor in synths.

small caps (like less than .001uF) are often G0G or NP0 - temperature
stable.  Whether they suffer from the other weaknesses of caps (dielectric
absorption, or modulation of capacitance with applied voltage) is still an issue.

>     But life is short...and I've substituted in many applicaitons
> figuring that the mfg. PROBABLY selected the cap I'm seeing because they
> got the BEST DEAL on a WAD of them :-).

This is the "either the engineer was stupid, or they were so clever that I don't
even recognize how clever they really are..." issue again.  Sub away if you don't
care, roll the dice. It will either work, or not. DON'T TRY THIS if you are on the

space shuttle  :^P

H^) harry