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Old 11th May 2010, 02:08 AM   #1
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Default Differing R values Tubelab SE

New to all of this, so bare with me. I started by soldering in the resistors today. Ordered with the parts list from the Tubelab website. I went through the board and checked all my resistor values before moving onto the next step. 5 resistors came up with different values than they were rated for:
R24 should be 120k ohms... instead is 72.5k ohms
R13 should be 120k ohms... instead is 72.1k oms
R7 should be 100k ohms... instead is 53.9k ohms
R21 should be 510 ohms... instead is 327 ohms
R10 should be 510 ohms... instead is 342 ohms

Is there something that I'm overlooking here? It appears that the values are half of what they are suppose to be. I have other resistors on the board, like R30 that's rated 120k ohms but read correct around 117k ohms. So, there doesn't seem to consistency other than its around half resistance on the problem resistors.

Any suggestions?

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Old 11th May 2010, 02:45 AM   #2
jrenkin is offline jrenkin  United States
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Seems like when you measure installed, you get some complex values that are due to resistors in parallel. You are not isolating the resistor alone. Take one out and check it. R30 for example has no other resistors connected both to it and ground, whereas the others do.
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Old 11th May 2010, 02:17 PM   #3
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As mentioned it is normal for the resistors to read different when they are connected into a complex circuit since you are measuring the entire circuit, not just the resistor. If you started with new parts there is no need to remove them again to measure them, The odds of getting a bad one are very low. If you use recycled parts it is always wise to measure before using.
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Old 11th May 2010, 09:52 PM   #4
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Yes, this makes sense. I'm learning a lot building this. Thanks for the help!
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