Is it normal for resistors to have big deviation?

[DomPal]

I have a marantz 2270. I checked the resistor values on the amp board and some of values are at least 1k ohm off. Some are 200ohm off while some are exact. Is that normal???

 

[raycarr00]

depending on the material: 10, 5, 1% ... 1k off?! I had a multimeter act-up several times when the battery was low. certainly you're testing with the power off and the meter set on ohms...get a better measurement if a leg is lifted. but off by a K?!

 

[Stereodiver]

If your testing them in circuit, yes you will get strange readings in some positions.

You’ll need to unsolder one leg and lift the resistor away from the board to get an accurate reading.

What’s the problem?

Good Luck!

 

[DomPal]

Ohh I’ll try to lift one leg and remeasure. I dont have any problem with it. It’s idling nicely and dc offset is at 0 so maybe it’s just strange readings when the resistors are in circuit. Thanks guys

 

[raycarr00]

The deviation without lifting a leg could be in the K's if the specific resistor is in the millions. Best to compare the color band, using a flashlight and magnifying glass, with digikey's resistor calculator. Might save a transistor or tube. Improve the sound.

 

[HPMguy]

In circuit can be iffy, but I don't think you should ever see HIGHER resistance than labeled. Only way that can happen is if the resistor is going open. Lower can easily be the circuit, which is why you usually have to lift one leg.

Carbon composition resistors are the worst for going high resistance with age. The brown ones with a molded body. Metal film and metal oxide film tend to be more stable. Wire wound I don't know, I suspect unless badly overheated they are usually good.

Carbon composition resistors also get noisy for the same reason they go high resistance -- microcracks in the resistive material lead to localized heating and tiny shifts in resistance and current across the cross section.

 

[EastPoint]

The carbon film resistors (not carbon comp) in vintage Pioneer and Marantz gear tend to test EXTREMELY accurate, usually within a few percent.

 

[dankik]

For a 10K 10% tolerance resistor it can be as much as 1K off. For a 1% resistor it can be 100 ohms off.

 

[spicer]

Ohh I’ll try to lift one leg and remeasure. I dont have any problem with it. It’s idling nicely and dc offset is at 0 so maybe it’s just strange readings when the resistors are in circuit. Thanks guys

If you're going to measure them in circuit compare them channel to channel and note any difference. That way what ever in the circuit might affect the measurement will produce the same affect for both channels and one can reasonably say good if within tolerances. The best way though is to lift one side of the component. Since it is working fine remember the adage that if one looks for trouble they are likely to find it, you are messing with a good and properly functioning circuit. Be thoughtful and careful.

 

[DomPal]

I lifted the resistors and it checked out. the R760 was reading 7.7kohm when in circuit then 10kohm when lifted. Thanks for the help peeps!

 

[avionic]

You will find most of the film and moxi resistors are 5% tolerance ( gold fourth band )

https://www.digikey.com/en/resource...ors/conversion-calculator-resistor-color-code

 

[raycarr00]

if the resistor tests strange or way out of specification in circuit, that's when a leg is lifted to verify. same with other components. metal films are the best for accuracy and low noise, but are not appropriate for all sections of circuits. flameproof resistors may be more appropriate.