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Resistor Troubleshooting

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Posted on November 20, 2020 at 16:32:25
ivan382
Audiophile

Posts: 49
Location: Chicago
Joined: June 2, 2005
 So I have two resistors for each channel. One, while in circuit, checks out pretty close to its rated value. The other one does not (too low). So, I removed it only to find out that it check out good too, but out of circuit. The only other difference is that one appears to have been replaced and is probably a quarter or half watt. The one checking out good, still on the board, is a one watt resistor.

So the only other anomaly is that the bad one had a trace came loose on the bottom but appears in tact. It does have another layer or more between.

Just a bad solder joint ?

 

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RE: Resistor Troubleshooting, posted on November 20, 2020 at 17:52:50
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 You have to measure resistors when they're out of the circuit. Otherwise, you might be measuring other resistance in parallel, which will always yield a lower resistance measurement. If you remove them from the circuit and they measure good, then you can put them back into the circuit. On the other hand, if they measure bad when they're out of the circuit, then they're bad.

Incidentally, all you need to do is disconnect one end of the resistor to make the measurement. It doesn't matter which end you disconnect.

Good luck,
John Elison

 

RE: Resistor Troubleshooting, posted on November 20, 2020 at 22:21:35
AbeCollins
Audiophile

Posts: 46302
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
What John Elison said but I'll add a couple comments:

- Define "good" and "bad" in your post. What value SHOULD the resistors be? And what values are you measuring on your meter? Good and bad don't mean a thing as they have not been defined.

- Be sure not to touch the metal part of the test probes with your fingers because it is possible that your body resistance (in parallel) is throwing the measurements off. [Important when measuring relatively high resistance values. Not so important with lower values]



 

RE: Resistor Troubleshooting, posted on November 23, 2020 at 07:08:25
neolith
Audiophile

Posts: 4842
Location: Virginia
Joined: February 21, 2002
Contributor
  Since: December 2, 2004
 When resistors go bad, they go high. If the resistor is testing low in circuit, then there is another "connection" in parallel - a short, a leaky capacitor, etc.



"Our head is round in order to allow our thoughts to change direction." Francis Picabia

 

RE: Resistor Troubleshooting, posted on November 25, 2020 at 23:35:34
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 Is it POSSIBLE that the 1/4 was resistor is getting HOT in circuit and changing value?

The higher wattage resistors are OK with the current they are required to sink.....
Too much is never enough

 

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