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resistor variances

Started by scotheath, January 05, 2018, 06:15:23 PM

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scotheath

 Was reading a guys project build and he mentioned that he used all spec tested caps and resistors and premium ICs, transistors..
Got me thinking as I was ordering caps and resistors I don't already have to build a new OP fuzz pedal. I have always ordered from Tayda for all my builds minus a couple matched transistors for a Smoothie. I grabbed a pack of 1m resistors, had 5 left over, highest read .818 and lowest of the 5 was .723  those don't seem to be 1m resistors to me, especially since they are advertised as 1%, had similar results with the rest of the stuff I have  only 1 resistor I tested was actually what it said it was.
What kind of affect if any will having... IDK, 22 or 30 resistors in a build that aren't exactly what they say they are. Is that why they sell them in packs of 10 so you can pick out the 1s that are closest to spec ??

somnif

First question, how good is your multimeter? Its not entirely uncommon for them to be miscalibrated. If EVERYTHING you have is reading off spec, I'd think of the tool being the problem.

My experience with Tayda resistors is typically quite good in terms of "on spec". I've only ever had one real issue where they sent the wrong value.

reddesert

I have a cheap multimeter (one of those Harbor Freight $3-5 specials) and it consistently reads low for resistance on the 2Mohm range, and a little low on the 200Kohm.  My guess is that its current source is out of spec - I believe that is how the resistance ranges work - it sends a known current through the resistor and measures the voltage drop. The resistor assortment that I got on ebay, Tayda resistors, and various other things have all been within spec when measured with a more reliable meter.

BrianS

Plus one on what Somnif said.  Every Tayda resistor, with exception of one bag of 10 and it had to be a mismatch, have all been in spec.  My dmm runs about $25 and when the batteries get low it goes crazy.  You may want to check that and see if that helps.  I also have a $5 harbor freight dmm and it has always given pretty close readings to my other one. 

scotheath

IDK its a Mastercraft DMM ill check batteries and dig out my old meter and compare.
but am still curious of the affect out of spec resistors would have, if any

somnif

Quote from: scotheath on January 05, 2018, 07:27:22 PM
IDK its a Mastercraft DMM ill check batteries and dig out my old meter and compare.
but am still curious of the affect out of spec resistors would have, if any

It depends. if every resistor were out of spec, a bunch of stuff could happen. Voltage dividers could spit out the wrong juice, filters could cut the wrong frequencies, etc, etc, etc. If they're CLOSE to spec, the circuit would probably (maybe) work, but it would sound a bit funky. Some resistors matter more than others, and it depends on the circuit as to what specifically could happen.