NOS Carbon Comp Resistors in new Builds?

[Platefire]

  I've got a pretty good inventory of NOS CC resistors. Just at the appearance I would guess vintage 50's/60's. I am kind of hesitant about using these in a new builds because I'm thinking they have already outlived their shelf life and most likely my cause early problems in new builds. I haven't had the heart to use them simply because of the doubt rather they will hold up. Am I on the mark or is my fears un-warrented? Platefire

[RicharD]

I have a huge assortment of old CC's.  Some are in spec and some are >20% high.  I mainly use them for "period correct" repairs.  I've done some new builds using them searching for "mojo"..... whatever that might be.  I haven't had any problems with the ones that measure true, but OTOH I learned the hard way to measure them first.  There are 2 schools of thought:  "Smoke em if you got em" vs. "why beg for trouble".  Resistors are cheap and there's about everything else that appear to have a greater impact on tone.

[woolly]

if they fit, use 'em. probably better than the new stuff.

[CircuitButcher]

I seem to recall David Allen (who worked in the resistor industry) recommending 2 watt CC's on the plates of his Fenderesq models, which may not apply to higher gain circuits due to noise considerations.

Do carbon comps "drift" on the shelf over time?

If so, would that be caused by humidity, salt, urban air ect?

Just on drift, does it always increase the resistance, e.g. 82k becomes 100k?

[tubenit]

probably better than the new stuff.

Why is that? What makes them "better"?

With respect, Tubenit

[Fresh_Start]

probably better than the new stuff.

Why is that? What makes them "better"?

With respect, Tubenit

'Coz they're old, just like us!  Duh!

Cheers,

Chip

[Platefire]

For instance, for my latest new build I failed to order two new CC 33K input grid resistors for single inputs (not double) for the 5E3 channels. I found some 33K in my NOS inventory, out of four tested  installed the two closest tolorence to 33K on my board (not soldered) that measured very close to 33K----the problem is just the doubt of not being sure caused me to make another small order to Doug to pickup us some update CC 33K's. In building something to sell to someone else, I don't like having a doubt factor even though any new component could fail at any time. I guess the opinons on this is probably to subjective and you just have to do whatever you feel better about. I guess the real question here is----will a 50 year old CC resistor provide just as long of a service life as a current production???  That question maybe unanserable 

[sluckey]

Do carbon comps "drift" on the shelf over time?

yes

If so, would that be caused by humidity, salt, urban air ect?

CCs are made of carbon particles. Pack the particles very tightly for low values or loosely for high values. Over time, the particles will loosen up some, increasing the resistance value. This happens even in temp/humidity controlled environments.

Just on drift, does it always increase the resistance, e.g. 82k becomes 100k?

I've never seen a CC pulled from bench stock that had decreased in value.

[dwp]

NOS have heavier leads, look cooler, you can certainly tell in appearance, but how bout having to scrape the leads? they are greyed out with residue if they're old, I have had the cold solder issue not cleaning with sand cloth or a razor blade.....Also bags full that are way more than 5% off value, but no drifting issue. read and use accordingly.....

[sluckey]

but how bout having to scrape the leads?

I use a block eraser, the red rubber ones that are more abrasive than the gummy ones. #0000 steel wool works well too.

[CircuitButcher]

CCs are made of carbon particles. Pack the particles very tightly for low values or loosely for high values. Over time, the particles will loosen up some, increasing the resistance value. This happens even in temp/humidity controlled environments.

Appreciate the explanation - is there a typical life cycle in this aging process, where the particles settle to a stable value, or does do CCs continue to drift?

[sluckey]

It's probably connected to the ever expanding universe theory.   

[Platefire]

Well fuwey, I was installing my input jacks and discovered I was one short for my 1 meg to ground so guess what, I dug several out (brown/black/green)of my NOS bag.    I really blew it on my material list! So NOS ain't half bad in the absense of everything else.   I tried to squeeze it a bit to tighten up those cabon particals to bring it back into tolorance! 

BTW--Senior moment---I completly blew also on wiring my input jack--I had the ground going to the +grid, had the 1 meg going to + grid to switch with no ground attached to switch term which would would have been OK if I had the ground to switch instead of grid. Do you ever get confused on an imput jack?

[Platefire]

Yeah, my wife tells me I drive like an old man---I say back, well--I am an old man! Wuda u spect! 

Back on NOS resistors-I will not make another order to make up for resistors I missed on my material list--I will just install the closest measured NOS available but I will probably just use my NOS as extras for emergency--knowing myself would prefer all new stock. Hopefully I will do better on my material list next time. Plate

[dynaman1]

Aw hell, I've tons of old CC's I picked up at flea markets. Never had a problem with them. Honestly? I think their drift is half the fun of using them. I like surprises and I only measure them if I can't read the bands.

[Backwoods Joe]

Just make sure you check the ohmage of each resistor. I payed a lot of money for some 1 watt CC's from a very well known mail order company a few years ago to find out they were worse than 20% tolerance. 

[Platefire]

Thanks! I'm building this 5E3 circuit to sell so I really wanting to provide the buyer best leg up with a circuit that potinually can last for years and years without any problem if properly taken care of. So I'm not interested in expermenting with old stuff to find mojo but just wanting to deliver that original 5E3 circuit in a new condition that will provide long service. Platefire

[phsyconoodler]

Carbon comp resistors were often 'drifted' right out of the box.They had a 20% tolerance on most of them.who cares?Use them if they are within 20% and they will work fine.I really doubt you will hear any difference at all.

[Platefire]

Good Physco! about 20% CC drift matches my mental drift, so we got a good match! Maybe a good name for this amp "The Platefire 20%+or-" more or less! 

[billcreller]

 I had a big bunch of CCs until my brother came over a few weeks back, and I unloaded them all on him. He restores old radios, and says he checks them and uses them.  Even had a bunch of the really old style types, with the body-end-dot color markings. He got those too. Never used any CC resistors in my projects., and I don't buy into the mojo thing.

[Platefire]

In my stock of NOS CC resistor there is another type of resistor thats mixed in with the rest that has a little different shape and material(not metal) that are very precision. When I measure them they are almost right on the mark of their stated value. Only trouble they are not in values common for guitar amps. I used all the 100 Ohms up on grounding heater wiring. Platefire