Checking Resistor Values

[playonit]

I was just curious how many of you meter your resistors out of a labeled shipping bag that states the value before using them in your builds?? I meter anything that is loose and not labeled but on my latest build I took the individual shipping bag labeling as the gospel and it created all kind of grief for me and some of you with my questions to the group. I had a few problems with the bags not containing what they said value wise. ( I won’t name the vendor because they have been spot on in the past) any hooo learned my lesson and everything gets scrutinized now…. Probably should have been doing it from the git go….

[Structo]

Yeah I do because I don't want some component that is out of tolerance in my amp.

I usually order like 10 of each resistor that I need in a build then meter then to find the closest to the value.
Plus it's easy to make a mistake on the color code if the resistors are loose.

The resistors that are picked this way are then taped to a heavy piece of paper with the metered valued written by it.

[billyz]

I measure each and everyone. They don't have to be perfect but I have had them mislabeled from the packaging. And my eyes are not as good as they used to be. The colors look different depending on the background too.

[playonit]

Tom what is an except-able tolerance? for example I had a 1k5 that measured 1.41.. IIRC caps can +/- 10% but what about resistors?

[Structo]

It depends on the resistor and where in the circuit it is.

For plate and cathode resistors I use precision metal film at 1% if I can get them in the value I need.

If I can't find them in 1% then 2%.

I don't like to see more than a 5% shift in most resistors, but nowadays most resistors are pretty close to their rated value.

[ToneMerc]

During the build prestage I measure resistors/caps and cull the ones that don't meet my needs.

TM

[gearhead]

I always meter mine just before placing, cutting to size, and soldering. Not only reistors, but pots and caps. Also do continuity checks on switches, jacks, and sockets (lug to hole).

[Structo]

I also check caps as well.
They are notoriously out of range sometimes.

[vibratoking]

It's definitely good to verify the value. I use any component that is within it's tolerance. I can't afford to ignore parts and my ears aren't that good anyway.

nowadays most resistors are pretty close to their rated value.

I don't fully agree with that statement. If you are buying tight tolerance components it is true. If you are buying wider tolerance components then it is not. All of the components that meet the tight tolerances get sold that way. All that don't, but that still meet the wider spec get sold as wider tolerance parts. This process creates a hole in the wider tolerance devices and almost none will be within the tight tolerance limits around the nominal value.

[Drumslinger]

i check every component that i can measure before setting solder to it.

[Phil_S]

I've got some 5K 3W that came off a roll. The are black and 5K is printed on them. They are taped together at the ends and the first few metered OK, so I sometimes don't bother with those.

I always meter the striped ones. I meter them when I remove them from the bag (when I picking the parts), and I meter them before I put them in the circuit.

[selloutrr]

Personally I buy in bulk of 500 to 1000 resistors per value for the price point discount. Using an app on my Ipod touch I compare the resistor with a color code calculator to confirm the banding to the label. Then using the fluke 867B I test each and every resistor by hand, I make 3 main piles while i test.

Pile 1 - Close with in .5% of the value.

Pile 2 - With in tolorence but not exact.

Pile 3 - Not in tolorence.

I then go back to Pile 1 and seperate the pile based on exactly on spec, over spec and under spec. label baggies and put them in, file them in the storage bin. I seldom keep piles 2 or 3. I do it as a good bad test and a way to stay focused. Otherwise It's easy to knod off.

I pull the good ones and send the bad ones back. I'd rather spend a couple dollars restocking fee then store resistors I'll never use.

When it comes to bulk parts orders I like to use large parts depots like Digikey or Mouser, because If I do have a problem they fix it promptly and hastle free. As nice as it is to support the little guy, It's often a head ache for everyone envolved if the order is wrong. Not to mention the parts are sold for a premium not a discount. The last time I ordered parts from a Mom and Pop shop they all came together in a zip lock freezer bag. - Charming! get your meter out! Even my smallest orders from a parts depot come in individual bags with labels.

It's not uncommon to have 10 or less exactly on spec out of 1000 units, but maybe as many as 100 within .05%.

I set down and metered all the parts for the trainwreck builds and I was pretty dissapointed with the swing on the values. Out of 50,000+ pieces tested I had less then 100 exactly on spec parts. I picked the best or closest matched parts when making sets. i.e. instead of using 1 perfect spec 100k resistor and one of a different value, when I need multiples, I picked 99.96K which I had 11 of.

[M Fowler]

I was wondering where you guys find resistors that are within value.

Mine rarely are within 5% and I asumed that was the way things are with the component supplies available.

[FYL]

It's not uncommon to have 10 or less exactly on spec out of 1000 units, but maybe as many as 100 within .05%.

Once soldered the values will be off by ±5% or more depending on the type and mounting method. Why bother?

Vintage amps used ±20% parts most of the time, ±10% for quality stuff and recent models. I use ±5% parts, test all of them and keep those in spec - something like 99.9%.

[Bob-I]

I meter every wingle son... I'm almost completely colorblind and I don't trust the baggy labels.