Which way do carbon comp resistors drift?

[jaysg]

I've been tormenting an early 70's pedal and everything I pull has drifted up, on the order of 17 to 24% above nominal.  Just wondering if it's random or always up.

[Seljer]

I guess up would be the logical way for resistor's values to drifts, as as they get older, their ability as a conductor weakens, which would mean their resistance would become larger

also, a lot of those old 70s pedals might not have been using high tolerance parts in the first place (more than 5%?)

[lacto]

Agree. Resistance drifts higher.

[markphaser]

The conductances changes tho thats the recipical of resistance

In tween 50's fender amps the fixed bias and B+ voltages are 20% or 40% or 60% higher than the schematic values
so lots of more current through the component more conductances

Why is and are the Fixed bias and B+ voltages 20% or 40% or 60% higher than the schematic values?
If the tubes,filter caps,recifier all check find then its down to the component level of the resistor values
this could stress out the amp because it has more conductance and current is higher

All the resistors values are all difference higher and lower from either heat or age(chemical breakdown)

[Paul Perry (Frostwave)]

I agree that usually comp resistors increase in value (but not always, and not by any standard amount).
But if I took a box apart and ALL the resistors were  17 to 24% high, I would check a known modern 1% resistor, as a "sanity check" in case your meter has a flat battery. I've been there
Note that if a meter was reading 20% high (whihc it could, with a flat battery, depending on design) then all those  resistors would be within 5% of nominal value...
It's never a bad thing to have a couple of "guaranteed" resistors tucked away.

[markphaser]

what u mean by flat battery?

[Somicide]

"weak" battery.  Dying, etc.  TMYK

[Paul Perry (Frostwave)]

I never stopped to wonder why in English a discharged battery is called "flat"!
What are they called in other languages? Apart from *&@#ed?

Edit: a suggestion from the net:
"A battery is called "flat" if it fails to discharge. A voltmeter reading its discharge would read a flat line near the bottom of the scale. I'm not sure why it's called flat, except that there's no reading that produces a rising line. You've heard of flat-line as a verb, of course. A patient whose heart rhythms produce only a flat line on an oscilloscope (and therefore no rhythm, no discharge) is said to be flat-lining. "

[Seljer]

Beer can also go flat ...and other carbonated beverages too

[hairyandy]

Beer can also go flat ...and other carbonated beverages too

I hate that.

Andy

[Sir H C]

The conductances changes tho thats the recipical of resistance

In tween 50's fender amps the fixed bias and B+ voltages are 20% or 40% or 60% higher than the schematic values
so lots of more current through the component more conductances

Why is and are the Fixed bias and B+ voltages 20% or 40% or 60% higher than the schematic values?
If the tubes,filter caps,recifier all check find then its down to the component level of the resistor values
this could stress out the amp because it has more conductance and current is higher

All the resistors values are all difference higher and lower from either heat or age(chemical breakdown)

60%?  You are on crack.

10-20%?  Because they were designed for 110 and you have 125 volts around alot.

Carbon Comps go up with heat.  That used to be how they would trim gear with 20% resistors.  Wire it up, test it, if R is low for the needed circuit then you heat it up and it will go slightly higher.  IF it is too high, then you start over.

[markphaser]

The B+ and Biasing voltages are way way "higher" then the fender schematic values what would cause this then?