[R-390] Resistors

[Charles Steinmetz]

Bob wrote:

> The gotcha is that the 270K resistor in the circuit at 30 MHz is actually presenting 150K. The circuit was designed
> for 150K rather than the 270K. It shows 270K since that’s what is marked on the carbon comp resistor. If you are
> going to replace them, you need to take that into account.

That differential is more than 10x greater than any reactance effect 
I've ever observed in an actual, new-condition CC resistor.  There may 
be CCs that measure like that, but not quality resistors in new condition.

In the actual CC resistors I've tested, a 270k CC will operate within 5% 
of nominal through HF into VHF.  Note that most CCs in boatanchors were 
originally rated +/- 10%, with a few rated +/-5%.  Also, note that a 
390/390A will work just fine (and meet spec) with resistors in most 
positions at +/- 50% (which is even further from nominal than the 
270/150 example given, so even if someone did happen to get a 270k CC 
that exhibited 150k at 30MHz, the radio would almost certainly still 
meet spec.  But, as noted above, things are not *nearly* that bad in 
real life.)

Best regards,

Charles