Odd Resistor values - Need your thoughts

Scott C

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Recently completed populating a dezbaz repro WG K6100 Input Protection PCB. When completed I noticed several of the resistors appeared to have the same color bands (markings), so I measured them and found the readings are confusing. For example, a resistor that should measure around 27K is measuring 8.8K, while the visually matching 1.2K resistor by it is measuring 0.9K. These are all blue base color resistors from Mouser and I believe the brand is KOA. While I need to check the manufacturer for the non-blue base (tan) 22K resistors, they are measuring 21.9K, which is well within tolerances.

I know these were installed correctly per the Mouser packaging, so is something in the circuit causing this or did Mouser get these mixed-up? I'm just confused on how two identically labeled resistors can have drastically different measurements (a little sure, due to tolerances, but more than 3 ohms, while being nowhere near their supposed rating)???

Ideas?

I'll post a good picture showing the repro IP PCB and resistors.

Scott C.
 
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If I'm understanding you correctly, you are testing resistors in circuit. You must unsolder one end to get a proper reading.
Yes, you are correct. My understanding is resistors can be tested in circuit, with the understanding the measurements will drop a little. Certainly not 27K to 8.8K. If my understanding is entirely wrong, then thanks for setting me straight.

I'm trying to attach the pictures now.

Scott C.
 
As I can't get the pictures to upload or link correctly from Tapatalk, I reviewed other pics of that completed board and there is no way those two resistors should look (be color labeled) the same, so I'm going to pull that resistor and replace. I will need to check all of the other resistors too. Thanks.

Scott C.
 
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There is some truth to what you mention above, but it all depends on how that trace is ran. To get a true reading, either lift a resistor leg, or completely pull it and test. Only the color bands will(should) identify the resistor, the casing colors don't matter, as different companies use different casing colors.
 
pull 1 leg.

there are countless resisters on chassis i work on that will read anywhere from almost a dead short to just under 5% of their value in circuit.

here is a prime example.
there are 2 on the K7 in the vertical circuit R98/99 that read a dead short in circuit even tho they are 2.2K resistors.

this is a fact.

if you don't believe it, get a working or non working K7000 it does not matter, and see for yourself, test them in circuit, then pull 1 leg and measure again.

pull the leg and get a proper reading or keep guessing if it is correct or not.

it's better to be safe than sorry:):)

Peace
Buffett
 
pull 1 leg.

there are countless resisters on chassis i work on that will read anywhere from almost a dead short to just under 5% of their value in circuit.

here is a prime example.
there are 2 on the K7 in the vertical circuit R98/99 that read a dead short in circuit even tho they are 2.2K resistors.

this is a fact.

if you don't believe it, get a working or non working K7000 it does not matter, and see for yourself, test them in circuit, then pull 1 leg and measure again.

pull the leg and get a proper reading or keep guessing if it is correct or not.

it's better to be safe than sorry:):)

Peace
Buffett
Thanks to everyone for the good info. I'll pull those and several more to ensure they are the proper resistance. Mostly what this teaches me is to test the resistors BEFORE installion. Wish I understood this before replacing 20 resistors on a 6100 deflection board. 😣

Scott C.
 
Thanks to everyone for the good info. I'll pull those and several more to ensure they are the proper resistance. Mostly what this teaches me is to test the resistors BEFORE installion. Wish I understood this before replacing 20 resistors on a 6100 deflection board. ��

Scott C.
Update:

Well, the good news is the resistors I installed are the correct resistors. I used the resistor app to verify the colors and specs.

The bad news is that even using my desk light/magnifying glass the colors of several resistors looked the same or very similar. As a result, I pulled out my smartphone, used the camera to zoom in to better see the resistors, and said "Oh!". Evidently, my eyes were not seeing the colors correctly until I was able to see the resistors really close-up.

Sucks getting old!

Scott C.
 
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