When thinking about substituting components, I know that resistors are easily substituted within their 10%/5%/1% tolerances. But what about wattage on a resistor? Is it safe to do substitutions, say 1/4W when the schematic calls for 1/6W. What about tolerances? I assume that I can substitute a 10ohm/1% if the schematic calls for a 10ohm/5%, but not the other way around.
For capacitors, the only substitutions I've done to date are installing higher voltages than specs...e.g., if my schematic calls for a 470uf/15V, I've subbed a 470uf/50V that I had lying about. Is that a safe practice? or should cap substitution be avoided?