Resistors?

[old_tv_nut]

Originally Posted by MadMan

Most are silver banded, and about 15 are right at the 10% mark and 7 are actually more like 15 or 20% out of whack. And I haven't even tested many yet.

I suppose I'll check voltage across them before replacing then? That's kind of what I'm getting here.

Regarding resistance tolerance: Right at the 10% mark is common and normal for carbon composition resistors, as the production line produced resistors with a wide variance. The 5% resistors were selected out by final testing, leaving resistors that were all higher than +5% or lower than -5%. Then the 10% resistors were selected out. Then the 20% reistors were selected out, and the remainder, worse than 20%, were discarded. So, don't worry about resistors that are just at +/- 10% unless 5% is called for.

As far as the voltage goes, I feel like I would be a little concerned if the resistor was rated for less than 1/2 the B+ voltage, but I would check the voltage in the actual use to feel safe.

Maybe someone here has more intuition about this.

What type of resistors are you replacing the carbon composition resistors with? I think the concern with voltage may be that carbon film resistors may be made with a spiral element, which means some fraction of the total voltage appears between each turn of the spiral and the adjacent turns. More turns means closer spacing, but a lower percent of the total on each turn. Which effect wins out then determines a voltage rating.