[R-390] Re: Parts Selection

[Tim Shoppa]

Perry writes:
>> Tim Wrote: There's nothing fundamentally
>> wrong with over-speccing replacements. Some
>> here get really carried away with it (e.g. putting
>> in 1% resistors everywhere...)

> Whoa!!  Time Out.  I do resemble them there remarks.  

> I champion 1% metal film resistor replacement
> over carbon comps for the following reasons. First
> they are decades more stable, have a  far lower
> noise factor, are smaller than, and are one third
> the price of carbon comps.  Also some "A"'s 2.2K
> resistors are underrated so with metal films you
> can double up in the same space or opt for the
> 3/4 watt rated Vishay series.

> The only other viable choice are 5% Carbon Films.  I
> haven't used them and they are almost the
> same price as metal films.

At the same time you seem to completely ignore the
widely available 5% metal films :-).

I have nothing against metal films. There's nothing
fundamentally wrong with putting a more precise
component in place of a burnt up component. I've
put in my share of 2.2K 5% metal films. I would be
even happier if there were 10% and 20% metal
films but these things do not practically exist.

The funny extra stripe on 1% resistors has something
to do with my reaction. It's an eye-attractor, saying
"hey I'm doing something that requires very specialized
parts here with tight tolerances".

Now there are a couple of high-precision resistors
in a 390A and I'm not opposed to replacing those
with 1% parts if they need it. (They don't burn up
like the 2.2K's, and some of them have something to
do with VU metering by my understanding.)

> As for mylar insulated caps they appear to be only
> available as third-tier parts. I know years ago
> they were extremely popular.  They are cheap.
> Neither Mouser or Digi-Key carry them. That
> personally raises a "red flag" regarding quality.

You're right! When I say mylar I am using terminology
I learned decades ago and you are perfectly correct,
they don't sell mylars anymore. I am really referring
to cheap, small, compact poly film caps unless I'm pulling
a part that's been in my junkbox for a couple of
decades. Thanks for the correction.

Tim.