Quote from: murrayatuptown on February 19, 2017, 02:16:12 PM
They drift in storage too...absorb humidity.
A once-retired engineer (working again to combat boredom) I crossed paths with, said it was standard to 'bake out' stored CC resistors to dry them before installing in (new) circuit boards.
CC resistors are a mixture of carbon black (conductor) and clay (insulator), with some phenolic binder to hold it all together. The ratio determines the resistance. The early phenolic coatings were often poorly applied or leaky, and moisture migrated in, swelling the grains and altering the characteristics.
The problem is that even when moisture is removed via baking the characteristics may not be fully restored to their original values.
CC is a horrible technology that was only used because it was inexpensive and nothing better existed. We have access to wonderful technology, like 1% metal film resistors, which are rock stable with voltage and age.
As long as one is not building circuits in the hundreds of MHz or GHz, metal film is the way to go.
Quote from: murrayatuptown on February 19, 2017, 02:16:12 PMI sold all my CC's on eBay, as advised...
Wise decision.
You thereby simultaneously reduced their wallet thickness while enhancing your own wallet thickness in a totally honest fashion.
The problem with CC mojo is that the varistor effects only show up with large voltage swings. So no magic could possibly occur for coupling stages, bias stages, etc. The only place it could possibly matter is at the plate, with the large voltage swings.
Otherwise the resistor is just out of spec at the rated voltage. (If a resistor's value declines with voltage, but the voltage is constant, than no mojo can occur. The resistor is just out of spec at that voltage.)
Most claims about CC mojo are a combination of wishful thinking by those who either want to believe they've made some magickal change to their amplifier, thereby establishing a special relationship with it and conferring bragging rights, or by vendors who make outright fabrications to increase sales.