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SMD resistor ID

peepermeeper

Feb 11, 2024
4
Joined
Feb 11, 2024
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Hello I need help identifying these what I believe are SMD resistors labeled R22 and R23 how does one go about finding what these are without a schematic is it just by size. I don't think I can accurately measure them since they are malfunctioning? I think the dot on top is just air bubbles in the conformal coating.Noob here.

Thank you
 

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H2814D

Nov 4, 2017
211
Joined
Nov 4, 2017
Messages
211
Hello I need help identifying these what I believe are SMD resistors labeled R22 and R23 how does one go about finding what these are without a schematic is it just by size. I don't think I can accurately measure them since they are malfunctioning? I think the dot on top is just air bubbles in the conformal coating.Noob here.

Thank you
You cannot do it by size. A resistor will have a resistance value, regardless of its physical size, and similar sized resistors can have different resistance values. Larger physical sizes usually have to do with the amount of current/wattage they can handle. When they are that small, they aren't always marked. Without a schematic, or an associated device component sheet, the likelihood of determining the actual resistance value will be difficult, unless you remove them from the board.

What you can do, however, is to take a multimeter and check the resistance value across each ends of the resistors. It looks like R20 and R21 are in like size and similar circuit placement, all of them doubled up and being next to the 620's. Note their locations in relation to R84, R86, and R88. See if all of R2X resistance values seem to match up closely. You may get lucky there. You should be able to check the resistance while they are on the board, unless the circuit they are in prevents that. But that is what I would try first.

The 620 resistors can be checked in the same way. You should be able to get a resistance value with a multimeter and they should all be very close, if they are good. If you find abnormally different values, you may have to remove them from the board to check them. In that case, you should be able to determine if they are still holding a similar value to the other ones. If so, there is probably nothing wrong with them.

Why do you think R22 and R23 are bad? I do see a bit of discoloration on the ends on the solder locations and the traces running from them. Resistors do dissipate some heat, and that is normal. It doesn't look like an abnormal or excessive darkening though. Is that why you think there is something wrong?

Your next step would be to take very clear photos of the top and bottom of the entire circuit board, provide us with a description of the problem you are having with the device, and tell us what kind of device you are troubleshooting. That usually helps the most.
 

peepermeeper

Feb 11, 2024
4
Joined
Feb 11, 2024
Messages
4
You cannot do it by size. A resistor will have a resistance value, regardless of its physical size, and similar sized resistors can have different resistance values. Larger physical sizes usually have to do with the amount of current/wattage they can handle. When they are that small, they aren't always marked. Without a schematic, or an associated device component sheet, the likelihood of determining the actual resistance value will be difficult, unless you remove them from the board.

What you can do, however, is to take a multimeter and check the resistance value across each ends of the resistors. It looks like R20 and R21 are in like size and similar circuit placement, all of them doubled up and being next to the 620's. Note their locations in relation to R84, R86, and R88. See if all of R2X resistance values seem to match up closely. You may get lucky there. You should be able to check the resistance while they are on the board, unless the circuit they are in prevents that. But that is what I would try first.

The 620 resistors can be checked in the same way. You should be able to get a resistance value with a multimeter and they should all be very close, if they are good. If you find abnormally different values, you may have to remove them from the board to check them. In that case, you should be able to determine if they are still holding a similar value to the other ones. If so, there is probably nothing wrong with them.

Why do you think R22 and R23 are bad? I do see a bit of discoloration on the ends on the solder locations and the traces running from them. Resistors do dissipate some heat, and that is normal. It doesn't look like an abnormal or excessive darkening though. Is that why you think there is something wrong?

Your next step would be to take very clear photos of the top and bottom of the entire circuit board, provide us with a description of the problem you are having with the device, and tell us what kind of device you are troubleshooting. That usually helps the most.

Thank you for the information I will work on some of this and hopefully get a diagnosis !! The device is a BMS for a onewheel xr. This company future motion is very closed down in regards to repair so I know I wont be able to get any proprietary schematics unfortunately. The problem I am having with the board is vague in terms of troubleshooting. The one wheel will not power on and gives me a code relating to a faulty BMS. This is also on the heels of a modification where I suspect I messed up a measurement on modifying the housing of this PCB and the battery which allowed the battery to press and possibly strike the PCB right where those two resistors are also when I power the BMS in situ those components instantly become scalding hot, I also see the discoloration which all leads me to believe that it is these resistors.
 

Delta Prime

Jul 29, 2020
1,810
Joined
Jul 29, 2020
Messages
1,810
hose two resistors are also when I power the BMS in situ those components instantly become scalding hot
Have you tried powering the BMS proximal or distal to
"in-situ"?
Are you a surgeon?
I am... on a one wheel XR.
I thrashed five in one week.
Now my five friends won't speak to me....
You got a bad cell in your battery pack! that's what you bumped making your mods.
Thank you for the information I will work on some of this and hopefully get a diagnosis !!
She doesn't no what shes talking about! How many diagnosis have you conducted using on your controller? For the BMS. (Rhetorical question).
Be very careful how you proceed
Show me your setup I want specifications... everything! even your mods. Your BMS is compensating for the defective cell. The only thing you can do only thing you can change is finding that cell extracted and replace it but that takes skill.
You're on an XR so you have skills . Proceed carefully. And welcome to Maker Pro!
 
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