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What does the etched (vs non-etched) RJ45 jack indicate?

I have 3 of the 2GB versions; only one works in the remote location powered by PoE. The two that do NOT work - the newest and oldest of the 3 - have an etched RJ45 jack.

The one that does work has no etching.

What do I ask for, when ordering, to receive the non-etched version?

Image shows Pis and the POE hat. Labeled with purchase dates. enter image description here

I move the SD Card and the POE HAT to each Pi in-turn for testing (eg all is identical except the Raspberry Pi itself).

Note: for the good Pi, once the ethernet cable is plugged in, within 2 seconds I see proper activity lights on the RJ45 jack. for the 2 'bad' Pis, I plug in the ethernet cable, and approx. 15 sec later both lights on the RJ45 jack flash on/off approx once per second. and the PI is not pingable (and doesn't grab an address from DHCP)

Note2: all 3 Pis work fine when powered by the USBC port (with and without the POE hat installed)

so, what does the etching mean?

or, any suggestions how to get the 2 non-working Pis to function.

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  • 1
    Probably best asking on the Raspberry Pi forums: raspberrypi.org/forums
    – CoderMike
    May 24, 2020 at 16:25
  • Baffled as normally the POE goes into the hat not the Pi. If you have plugged a POE link into the Pi directly you may have fried the Ethernet chip. Depends on how smart the injector is... as for engraving- cost as a guess.
    – user115418
    May 24, 2020 at 17:25
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    @Andyroo you are a bit behind the times, the 3B+ and 4B have a POE capable magjack and a connector to bring out the POE connections to a HAT.
    – Peter Green
    May 24, 2020 at 23:22
  • If you cat /proc/cpuinfo do all 3 pis have the same Revision and Model? (I'm sure there's been at least two releases of the pi 4)
    – Jaromanda X
    May 24, 2020 at 23:45
  • @JaromandaX they seem the same (I think this is the relevant info) 2020.04.06 (working) Revision : b03111 Serial : 100000003c0b9da7 Model : Raspberry Pi 4 Model B Rev 1.1 2020.05.18 (non-functional) Revision : b03111 Serial : 10000000505670db Model : Raspberry Pi 4 Model B Rev 1.1
    – SE-tinker
    May 25, 2020 at 5:20

2 Answers 2

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Posting this as answer because it 'solves' my final "how to get the 2 non-working Pis to function", but it doesn't address the topic; why is one of the 3 Pis different.

in short, now all three Pis work at the remote location powered via PoE.

All I did was cut the external plug off the ethernet cable and replace it.

This still leaves me wondering... what is special about the one Pi (sans etching) that it worked with the poor ethernet plug? (and how to order more of those fault tolerant Pis!!!?)

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You probably had a cable with non-standard wiring (perhaps a cross-over cable). Most RJ45-POE plugs assume the wiring is conform to the standard, which allows the manufacturer to use only 4 rectifiers. Some plugs accept POE with cross-over cables, at the expense of using twice as many diodes:

enter image description here

Apparently, the jack with no etching uses design 2, while the etched ones use design 1. Having said that, there is no guarantee that all jacks with no etching will be like that.

The etching in itself means nothing, if you order millions of pieces, manufacturers will offer pieces with and without labels or even with labels of your choice. You can also order whatever they have in stock, which may be a mix of different label schemes and parts with no labels. And if you need the pieces badly enough, you will even accept to overpay to get more expensive parts which are already in stock, instead of waiting for cheaper ones to be produced.

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