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I'm trying to find some certain pads on a monitor circuit board.

I found a cluster of pads that's marked as "A", I assume because there's no space to write what every single one is. And on the far right of the pad, there's a marking that says "a", and there are all the markings listed. The problem is - they're formatted as a list, so basically just one under another. How should I know which one is which? They're not just next to each other, some are on top or on bottom. So I can't just count them and proceed. Please, can you tell me which one is which? (Screenshot below)enter image description here

enter image description here

I searched for "reference designators clusters" but found nothing.

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    \$\begingroup\$ They look like test points for the components it is adjecent to. \$\endgroup\$ – Michel Keijzers Aug 15 at 13:08
  • \$\begingroup\$ I'm very new to PCB's, so could you please explain it a bit more? What are test points? \$\endgroup\$ – almarcDudeas Aug 15 at 13:11
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enter image description here

sorry for the poor drawing. i hope you can trace them.

I don't know the technical terminology for this. We do this whenever there is no space to place the reference designator at the same time it can't be dropped all together too. Then Reference designator will be grouped together but at some other point in the PCB where there is abundant space.
Care will be taken to see that the cluster will be exact replica of how it could have been in it's ideal place. The orientation of the components will be represented by the orientation of the reference designator.

Naming the clusters help in locating them easily. When it is easier we also have simply drawn lines from the component cluster till the label cluster.

If somebody knows the terminlogies please add. remote designators thanks to @RnDMonkey

Test points for Production
During production of the PCBs (say 1000 s of them) the testing will b done by automated machines. The machines do not need any text. They work by knowing the position of components. Here, they use those big round test points. Through these test points the machine can measure resistances, capacitances, inductances as well as voltages.

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  • \$\begingroup\$ Thank you, that is very helpful! \$\endgroup\$ – almarcDudeas Aug 15 at 13:42
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    \$\begingroup\$ Good answer, but I think it could be improved by explaining what this practice is in words as well as just the (rather self-explanatory, yes) picture. \$\endgroup\$ – Hearth Aug 15 at 16:26
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These look like test points, which are pads, pins or hooks used to test connections (to be able to place a oscilloscope or logic analyzer probe). This way developers can test if a certain voltage or signal is present; but to do this you must know the meaning of that point (pad in this case). It seems the text right of it might give a clue about the meaning.

For more info see: Wikipedia: Test Point.

As you can read, these are used during manufacturing or service, and not meant for 'users', that's why labeling is not 'needed'.

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  • \$\begingroup\$ Yes, I assume they are test points. Still, I need to know which one is which. \$\endgroup\$ – almarcDudeas Aug 15 at 13:20
  • \$\begingroup\$ If you follow the trace lines the test points are either one or both sides of the resistors adjecent to them. \$\endgroup\$ – Michel Keijzers Aug 15 at 13:28
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The test points are not on top of each other. The grouping you've showed has four test points (corresponding to the four net names in the label area) and pads for seven components (corresponding to the seven component names in the label area), some of them unpopulated. The test points are all round and circled in the silkscreen. There doesn't seem to be any ambiguity in positioning.

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I call these "remote designators" and as said by the helpful person with the illustration, these are meant to mimic the relative placement and orientation of the components they designate. Outlining the groups and using corresponding lookup letters is used when the group of designators is not close enough to the components to clearly represent them.

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I believe that this PCB has a multi function applications, and it depends on fitting or non fitting components on it. So regarding what you showed us in your picture there are some unfitting elements such as R125 and R126, who are responsible to enable the LED. So these test points are not for the customer service and are only necessary in the development stages, so companys leave this possibility open for them to make continuous improvements for their products.

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enter image description here

The white writing relates to the capacitors, resistors and information about the actual test points. The circular pads with white circles are test points for probes to multimeters, scopes or a bed of nails test fixture. So looking at this picture we can say that the top row of components are capacitors and only one is there cc06. The next row beginning with rr01 left to right are the resistors left to right 11 of them. The circular pads from left to right start with info vgma1 then go left to right. So the layout of the white writing to the right of the components etc relates to what is there. I design and build test fixtures all day every day in work. enter image description here

Here you can see a pbc in a fixture with the probe pins coming up underneath that touch the test points. Hope this helps

Here is your pcb marked to make sense enter image description here

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