How to find burnt resistor value. pdf download

How does one identify a burnt SMD resistor for replacement. PS: if i have no luck, i am thinking i can short out R, because R,R and L seems like some sort of high frequency filter, the wire left of the inductor is connected to the front banana jacks and the right is going to the digital section. This looks like a digital output judging by the opto-isolator i guess, perhaps a way to identify this is by following the traces and drawing a small schematic to judge the values from the rest of the circuit, you should start by removing both resistors.

BTW i couldnt find a data sheet for U likely an opto isolator where does the other end of L go? It takes a touch of genius, and a lot of courage to move in the opposite direction". Hi, my guess seems right, i shorted out the resistor and viola the meter is back.

The readings are a bit lower than expected, but this is on all ranges so im guessing its a calibration issue. However, the error codes have gone up in count. With the old blown resistors i had 4 error, now ive replaced them with The Universal resistor 1kOhm ofc and i have 9 errors. Does anyone have a keithley they could pop open and read off the values for the resistors please? If you post a larger picture showing where that is I can open mine up and look.

Also, any idea what caused this? The following users thanked this post: mcinque. Quote from: FlyingHacker on August 31, , am. Quote from: h. Mickle T. Frequent Contributor Posts: Country:. The following users thanked this post: BillyD , mcinque , adilmalik.

Quote from: Mickle T. Quote from: adilmalik on August 31, , am. The following users thanked this post: h. Beat me to it on the pics. I am going to open mine up again soon anyway. I think I want to recap at least some of it. Quote from: azer on August 31, , pm. I dont think anything beyond U have suffered so just replace it and see what you get. BTW, anyone with this meter really ought to replace their filter caps if they haven't already.

At least the "Stone" brand caps are known to fail. Nothing too serious, i only noticed it when i removed all ambient noise from the room. Any ideas? Pretty amazing meter for less than the price of a Fluke 87V.

Mine was working at the time. The issue turned out to be a dirty gang switch, which I just sprayed with contact cleaner.

Of course I had to break the current cal seal to fix it. I never noticed this meter making much noise, but the case is always on. Might not be a bad idea to at least change those big uF caps including the one closer to the front of the unit, right next to the transformer. They are all placed too close to heat sources for my liking. Finally got the resistors and replaced them. Error codes still persist, but meter seems to be functioning correctly.

I believe one of the self test circuitry might have been damaged during the over voltage condition. Ive found the following: To check the operation of the internal current sources the meter outputs a constant current and measures the voltage across the precision caddock resistor divider.

These are 2 resistors, bonded as a ceramic sandwich. Look at the resistor so the group of 3 or 4 color bands are on the left side. These are sometimes followed by a gap, then an additional color band. Read the color bands from left to right. The colors on the first 2 or 3 bands correspond to numbers from 0 to 9, which represent the significant digits of the resistor's ohmic value.

The last band gives the multiplier. For example, a resistor with brown, green and green bands is rated at 15 mega-ohms 15,, ohms. Read the color on the last color band, which is farthest right. This represents the tolerance of the resistor. If there is no color band, the tolerance is 20 percent. Most resistors have no band, a silver band or a gold band, but you may find resistors with other colors.

The tolerance color code is as follows: [3] X Research source. Memorize a mnemonic for resistors. Several exist, so choose the one that you won't forget. Remember that the first color is black, and afterward each first letter corresponds to a color in order from 0 to 9. Some popular mnemonic devices include: [4] X Research source "Bad beer rots our young guts but vodka goes well.

Method 2. Surface mounted resistors are rectangular in shape with leads that extend from opposite sides or the same side and are bent downward for mounting on circuit boards.

Some resistors have contact plates on the bottom. Read the 3 or 4 numbers on the resistor. The first 2 or 3 represent the significant digits and the last indicates the number of 0s that should follow. For example, a resistor reading indicates a rating of 12, ohms or 1. Compare the letter at the end of the code with the tolerance it represents. Check to see if there is a letter "R" within the numeric code.

This indicates a very small resistor, and the letter takes the place of a decimal point. For instance, a 5R5 resistor is rated at 5. Did you know you can get answers researched by wikiHow Staff? Unlock staff-researched answers by supporting wikiHow. Not Helpful 0 Helpful 0. Resistors are typically used to limit electrical flow, not step it down.

What you should use is what is called a "step-down transformer. Not Helpful 11 Helpful Hold the five watt resistor and measure by using a multmeter or by reading the color coding. Not Helpful 3 Helpful 3. What is code system relating to these?

I have no schematic and want to do in-circuit troubleshooting. Drew Hawkins1. They may be markings that are specific to the electronic or are no longer used. Try researching outdated resistor markings online to identify them. Not Helpful 0 Helpful 1. Black represents a value of 0 and are likely shorting links, since these components have zero resistance. You can find them at electronic supply stores, computer stores, and online.

First, find the number of ohms for the resisters, then convert the ohms to watts. Include your email address to get a message when this question is answered. Submit a Tip All tip submissions are carefully reviewed before being published. You Might Also Like How to. How to. About This Article. Co-authored by:. Co-authors: Updated: June 3, Categories: Electrical and Electronic Circuits.