Parts replacement

[multi-volti at MULTI-VOLTI.COM]

My opinion only:

Carbon composition resistors are getting harder to find. Replacing them with
carbon film or metal film is fine if you're an audio guy and want lower
noise, etc. But if you're an RF guy (HW-12...yup, RF gear), the modern film
resistors are usually laser trimmed in a spiral pattern, which creates a
more inductive resistor than the blob of carbon 'composition'. Indeed, (how
literary sounding, eh?) a concern in the 'old days' at high frequency was
the capacitance between the ends of carbon composition resistor terminals. I
can't visualize CC resistors having more capacitance
than a spiral cut film one, but I guess the issue was that at some
frequency, every component begins to look less ideal.

Spiral-cut resistors probably have higher inductance and thus might affect
an RF circuit...not enough to make it work incorrectly, but enough to make
some measurable difference.

If your CC resistors are drifting, you may not have much choice. A little
inductance added is better than 150% extra resistance!

Capacitors...you have to be careful making changes...you have to know what
you're doing...like not trying to use hi-k (or most other) ceramic caps
where frequency stable silvered micas were, not using polyester in place of
polypropylene if high ac voltages are present, and other things.

In frequency-stable stages, there might be a mix of ceramic discs with
various temperature coefficients...changing the mix might give you different
drift characteristics.

Enough already....

Murray



----- Original Message -----
From: "Hunt, Keith" <keith.hunt at SFCC.EDU>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Wednesday, November 20, 2002 12:06 PM
Subject: Parts replacement


> Is there any advantage on using higher quality caps and resistors in a
> HW 12A rebuild?
> Many Thanks !
>
> -----------------------------------------------------------
> This list is a public service of the City of Tempe, Arizona
> -----------------------------------------------------------
>
> Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
> To post - HEATH at LISTSERV.TEMPE.GOV
> Archives - http://interactive.tempe.gov/archives/HEATH.html
>

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://interactive.tempe.gov/archives/HEATH.html