SMD resistor code

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Shagreobe

New Member

• Nov 4, 2023

• #1

Hi all. I ran across an SMD resistor marked with just an "E" (or maybe "3") What is this? havent seen only 1 digit/letter before except for 0 ohm of course. It measures about 12.8R in one direction and around .9M the other way. (In circuit of course)
Any Idea what the marking is?

 

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Diver300

Well-Known Member

Most Helpful Member

• Nov 4, 2023

• #2

If it measures differently in each direction, it's not a resistor. It is probably a diode of some sort, assuming you didn't get a bad connection when measuring it, and that it has been measured when not fitted to a circuit board.

 

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canadaelk

Active Member

• Nov 4, 2023

• #3

Why do you believe it is a resistor? Check here: https://smd.yooneed.one/code3300.html. There are other code sheets with additional codes o search. E

 

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For The Popcorn

Well-Known Member

Most Helpful Member

• Nov 4, 2023

• #4

SMD resistors may use a strictly numeric code, or an alpha-numeric code for 1% resistors. Check this reference.

 

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Shagreobe

New Member

• Nov 6, 2023

• #5

Here is a pic of it. Looks like every other resistor I've seen?

 

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• 20231103_143459.jpg

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Nigel Goodwin

Super Moderator

Most Helpful Member

• Nov 6, 2023

• #6

Shagreobe said:

Here is a pic of it. Looks like every other resistor I've seen?

Click to expand...

Or many capacitors, many diodes etc, etc. A fuse is a fair possibility as well.

It's a bit suspicious when the other resistors in the picture are blue, and clearly labelled as Rxxx.

Why are you investigating it?, is the unit faulty?, and have you fault found to this point?.

 

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Shagreobe

New Member

• Nov 6, 2023

• #7

Troubleshooting a problem, and noticed the odd looking thing. Never see one with just 1 letter. It goes to the center pin of the 7805 vr

 

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schmitt trigger

Well-Known Member

Most Helpful Member

• Nov 6, 2023

• #8

The CAD draftsman who laid out this board should be obligated to troubleshoot one himself; it is horrible!
Not only many labels are placed on top of solder joints, obscuring characters, but there are components without labels. For instance, the ceramic cap on the bottom left corner.
And the “mystery device” is labeled as a “P”, which means exactly… what? A photodiode? Unlikely as it doesn’t seem to have a transparent window.

EDIT: it goes to the center pin of the voltage regulator. Which in a 7805 is ground.

 

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Shagreobe

New Member

• Nov 6, 2023

• #9

I uncoveed some solder joints on the vr and can now see the "f" in front ]of the number so I guess it's a fuse