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  1. #1
    Shunt resistor part numbers?

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    Shunt resistor part numbers?
    One example:

    I'm fixing an 820-00281-A/A1707, and a slew of cold solder joints has me replacing hundreds of SMCs. The 4 pin 'current sensing' resistors like R5750 are:

    0306-SHORT
    MF
    1/3W
    1%
    0.005

    ...used to sense current in lots of places with INA210s, and I think INA214s, among others. My only problem is that I can't locate exact part numbers for these guys. they secure to LB with 2 'normal' pads, and 2 elongated ones:

    smaller 2020-06-06 191126.png

    Same problem with the crystals, as I can't match the schematic specs to digikey lookups, but that is another post...

  2. #2
    Shunt resistor part numbers?
    pm-r's Avatar
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    I'm sorry, I sure can't help, but i certainly respect what people like you can do.

    Heck, just reading your post is like me trying to read a different language i have never come across, but i do get a gist for what you are attempting to do.

    Sorry and good luck, and maybe some guru will pipe up with the answers for you.

    I don't even know of a Mac help site that would be of any use for you that i could recommend.



    - Patrick
    ======

  3. #3
    Shunt resistor part numbers?
    IWT's Avatar
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    @Holes Flow

    Like Patrick, I am in new of you in the work you are attempting.

    I was wondering if these part numbers and details might be found on ifixit.com (https://www.ifixit.com)?

    That is the number one site for this sort of thing.

    Ian
    Ian

  4. #4
    Shunt resistor part numbers?
    krs's Avatar
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    Like Patrick and Ian, I can’t help either, but I’m not sure I understand what you are looking for.

    The IAN210 series you reference are 6 and 10 terminal devices, but then the reference R5750 is a 4-terminal device.

    So are you looking for the part number for the R5750 on that board you are referencing?
    Where does the screen shot come from that you included in your post - would that document not show the part number for R5750?

    As to the crystals, there is a possibility that those are not commercial items but a “special” for Apple.
    I worked in a High Tech company and if the design calls for say a crystal with a better tolerance than the standard one, the manufacturer would sort them for us an apply a special product code - for an additional fee of course.
    Something to keep in mind as a possibility.

  5. #5
    Shunt resistor part numbers?

    Member Since
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    Pat,

    Doing component level repair is really all about the tools, and a background in electronics. Mine is from the military and as a civilian, but it doesn't take but a few weeks with YouTube, or volunteer courses like this one, and you are all set!

    Quote Originally Posted by pm-r View Post
    "Heck, just reading your post is like me trying to read a different language i have never come across, but i do get a gist for what you are attempting to do."
    Let me see if I can decode it enough to capture your interest:

    -The purpose of the above R5750 is actually quite simple: It is there to allow a device to the right to measure a voltage.
    -On the left, you will see that the aptly named PP3V3_SSD_ISNS_R signal supplies a voltage, and PP3V3_SSD_LIM is the return. Just look at the arrows."LIM", as you can imagine, is for "current LIMiting".
    -"ISNS_R" stands for I (symbol for 'current') SeNSe Resistor. Note the 2 signals on pins 3 & 4 with the suffixes _P (Positive) and _N (Negative).
    -"Ohm's Law" shows that when current flows through a resistor, a voltage 'drop' forms across the resistor.
    -This means that you can measure how much current is flowing through a resistor by measuring the voltage dropped across it. Since I = E/R (formula meaning "Current = Voltage dropped (i.e. divided by) over the known Resistance"), we can measure to see if there is too much current going through this circuit, I would assume for the SSD.
    -So for an example, if we know the resistor's value is 10 Ohm (ohm = measurement value of resistance), and we measure 2 Volts (the 'E' value, volts are measured in Volts), Current ("I") is simply E/R, or 2V/10 Ohms or 0.2 Amperes ("I" for current is measured in Amps).
    -0.2 Amps is also called "200 millAmps", or simply "200mA".
    -If, for example, that measuring device off to the right (the INA210s & INA214s I mentioned in OP) shuts down the power rail PP3V3_SSD when current draw is over, say, 150mA, then the above condition shows a [partial] short to ground, and to protect more expensive electronics, it will turn that power bus off, or something.

    Here is how the symbols on the schematic above break down:

    OMIT - Can mean either do not put on the board at all, or only to not put it on automatically with machines that place these tiny parts (robot arms). I don't know which in this case.
    0306-SHORT - This means the size of the device is EIA number 0306, which you can look up at a place like (I have no permissions to put in this comment): Mechanical Dimensions for Capacitor Chip Devices, SM Package Sizes So, 0306 is 0.063" x 0.032" x 0.013" (nobody memorizes, so a chart is handy!)... The "SHORT" means that at just 0.005 Ohms, it is essentially (but not quite) a short (i.e., no resistance at all!).

    Q: "Why such a low resistance?"
    A: Because it the resistor was much more resistive, it would start taking signal away from the (in this case) SSD subsystem. We want our measurement parts to be as unobtrusive as possible.

    MF - Metal Film (the type of material the actual resistor is made of)
    1/3W - this resistor can only take 1/3 of a Watt ("W") before it will blow.

    note: Watts can be calculated several ways, with one of them being I x E, or Current x Voltage. Too much of either, and it will blow and in overheating present an 'open' circuit (no connection at all between pins 1 & 2).

    1% - Tolerance - The value of resistance is guaranteed by the manufacturer to fall between + or - 1% of the stated value. This isn't followed closely by off-brand suppliers...
    0.005 - This is the actual resistance in Ohms. You will see things like 5k for 5,000 ohms, 2M for 2,000,000 Ohms, and other metric 'multipliers'.
    R5750 - This is Apple's designation. Good for finding on a drawing or schematic, like a cross-reference, but nothing to do with the part itself, except R is for Resistor, C is for Capacitor, D is for Diode, Q is for transistor, U is for microcontrollers or simple ICs, etc.

    Once you know how to decode these components, they aren't so intimidating.

    -pat

    Quote Originally Posted by pm-r View Post
    I'm sorry, I sure can't help, but i certainly respect what people like you can do.
    Heck, just reading your post is like me trying to read a different language i have never come across, but i do get a gist for what you are attempting to do.
    ======
    Last edited by Holes Flow; 06-08-2020 at 04:25 PM.

  6. #6
    Shunt resistor part numbers?

    Member Since
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    Thanks, @krs, I will. The fact that I couldn't find matches on distributor 'configurator' web pages is disheartening...

  7. #7
    Shunt resistor part numbers?

    Member Since
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    About the screenshot:

    The screenshot above is from the schematic for a 2017 MBP, A1707, Logic Board 820-00281-A

    I've seen some folks get weird about links to boardview & schematic sites, but they are prevalent, and as a result, should not be paid for. So here is a link that should pass the acid test.

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