[R-390] Resistor Tolerances

[Dave Merrill]

On Mon, 29 Jul 2002, Thomas W Leiper wrote:

> On Mon, 29 Jul 2002 07:45:03 -0400 "scott" <polaraligned@earthlink.net>
> writes:
> ...
> > Most, if not all, of the resistors seem to be 10% in my
> > modules and I am thinking that this was just a military
> > requirement rather than an necessity.
> 
> I am "resisting" the "requirement" to respond, but my
> "tolerances" have been exceeded by over 10%.
> 
> Certainly any aspect of the original construction was a
> military requirement and not necessarily an operational
> requirement since many things can be changed that
> actually improve performance in some ways. But by
> trying to hold tolerances tight, they are trying to hold
> the performance to a predictable level so that when
> it is put into service they know what to expect, and
> not have one radio being "hot" and another a "dud".

While in college, I had a part time job as a tech in the TV 
engineering department of a now-defunct Chicago manufacturer.
This was back in the days when all the BW sets were tube and
the color sets were hybrid.

Part of my job was to do 'r-box engineering' on existing
designs - remove a 10% resistor, substitute a resistor box
and run the value +/- 20% from the schematic value to determine
if a 20% part could be used.  Saving a fraction of a cent
here and there adds up when you're making thousands of units.
Much different design objective than military gear where cost
isn't the most important criteria.

72.../dave N9ZC