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   Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:00:46 JST Graham Sutherland / Polynomial

   my NAS died a couple of days ago with zero sign of life. no lights at all on the board, not even standby LEDs. it's going to my UPS, so I checked that I was seeing 230V at the cable, and I did. so I figured the PSU is dead, because the motherboard would need to be ultrafucked for it to show literally no signs of life.

   ordered a new PSU. it arrives. swap it in, aaaaand... nothing. ugh. so is the board dead? maybe a hard short over +5VSB or something?

   so I start digging further.

   • Embed this notice
     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:00:35 JST Graham Sutherland / Polynomial

     in reply to

     wait it gets EVEN MORE CURSED

     I grabbed a BS1363 (UK plug) to IEC cable. I plugged the problematic IEC-IEC cable into it. then I grabbed another known-good IEC-IEC and plugged it into that. so I have a chain of BS1363-IEC, IEC-IEC (bad), IEC-IEC (good).

     I get 230V at the output.

     I plug it into the old PSU.

     it will not power on.

     CABLE'S HAUNTED

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     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:00:37 JST Graham Sutherland / Polynomial

     in reply to

     wiggling the connector around does nothing though. I see no fluctuation on the multimeter at all and, no matter how I apply pressure to either end, the old PSU (which works fine, so sadly I bought a new PSU for £120 for no reason) will not power on with this cable. extremely bizarre.

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     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:00:38 JST Graham Sutherland / Polynomial

     in reply to

     the only thing I can think of is if the cable somehow thermal cycled in a weird way and the contacts are *only just* making contact so when plugged in it's showing 230V when unloaded but the contact resistance is high enough to tank the mains voltage as soon as it tries to power on? but then you'd think the PSU would hiccup rather than just not powering on (I guess maybe mains UVLO protection could prevent that or something? idk)

     this is one of the weirdest failure cases I've ever had

   • Embed this notice
     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:00:39 JST Graham Sutherland / Polynomial

     in reply to

     I've tested continuity and resistance. the cable is fine. L-L, N-N, G-G, no continuity between the lines, resistance reads good (within 10% of other IECs I have). it's been powering my NAS for *years* without issue. I get 230V on the output when I plug it in. but *neither* my old PSU or new PSU will power on when plugged into it.

     I am *SO* confused

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     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:00:41 JST Graham Sutherland / Polynomial

     in reply to

     this is a straight IEC-IEC, no fuse, it's just regular copper wire. and I read 230VAC just fine over it. but the PSU won't power up with that cable.

   • Embed this notice
     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:00:42 JST Graham Sutherland / Polynomial

     in reply to

     I was fumbling around a bit trying to plug stuff in 'cos it's pretty cramped back there, and when I look in with my phone light I notice that the new cable is actually plugged into the *exact same port* the old cable was. the port is fine.

     plug the old cable back in and try it. doesn't work. plug the new cable in. it works.

     what the actual fuck

   • Embed this notice
     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:00:44 JST Graham Sutherland / Polynomial

     in reply to

     so I go downstairs with it and I'm about to file an RMA, and I think "hmm, maybe it just doesn't like the UPS? better check before I RMA it".

     so I plug it into an IEC cable downstairs, bridge PS_ON, and bam! works.

     so is it the UPS????

     I go back upstairs, try again, yup still dead. and I'm still seeing 230V.

     I grab a new IEC-IEC lead to test another port on the UPS, and it works! so what, one of the UPS ports is somehow presenting 230V but... not good enough 230V to work? wtf

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     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:00:45 JST Graham Sutherland / Polynomial

     in reply to

     first: gotta verify that the new PSU works. I measure +5VSB on the ATX24 and get 0V. so I bridge PS_ON and GND, and check the other rails. nothing. I see the briefest flicker of a few mV, maybe, but it doesn't power up. I'm starting to think the new PSU is DOA and I just got super unlucky.

     I verify mains again. 230V on the dot. just to be sure, I go check that my multimeter is reading DC correctly. yup, it's fine.

     at this point I'm really thinking I just got a dead PSU, or the board killed it.

   • Embed this notice
     Ryan Castellucci (they/them) :nonbinary_flag: (ryanc@infosec.exchange)'s status on Wednesday, 08-Jan-2025 07:01:05 JST Ryan Castellucci (they/them) :nonbinary_flag:

     in reply to

     @gsuberland You were around for the thread where I discovered that ghost voltages are a thing, right?

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     Ryan Castellucci (they/them) :nonbinary_flag: (ryanc@infosec.exchange)'s status on Wednesday, 08-Jan-2025 07:02:57 JST Ryan Castellucci (they/them) :nonbinary_flag:

     in reply to

     @gsuberland There was a wire in my wall with something like 143V on it, yet when I grounded it with kynar wire the kynar wire survived.

   • Embed this notice
     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:02:59 JST Graham Sutherland / Polynomial

     in reply to

     • Ryan Castellucci (they/them) :nonbinary_flag:

     @ryanc ????

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     Ryan Castellucci (they/them) :nonbinary_flag: (ryanc@infosec.exchange)'s status on Wednesday, 08-Jan-2025 07:05:14 JST Ryan Castellucci (they/them) :nonbinary_flag:

     in reply to

     @gsuberland It's not even old, lolsob

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     Graham Sutherland / Polynomial (gsuberland@chaos.social)'s status on Wednesday, 08-Jan-2025 07:05:15 JST Graham Sutherland / Polynomial

     in reply to

     • Ryan Castellucci (they/them) :nonbinary_flag:

     @ryanc oh right yeah you get weird floating shit in old house wires

   • Embed this notice
     John Timaeus (johntimaeus@infosec.exchange)'s status on Wednesday, 08-Jan-2025 08:49:40 JST John Timaeus

     in reply to

     • Ryan Castellucci (they/them) :nonbinary_flag:

     @ryanc

     I had a 1920s house (US, so 110v standard) that would put 220 to the light over the stove if you turned on the garbage disposal while the microwave was running. Burned out a lot of incandescent bulbs. Made the first CFL I put in explode at the base.

     There were also outlets with constant 110 between neutral and ground, 220 between live and ground.

     I spent a lot on wire for that place.

     @gsuberland

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     Ryan Castellucci (they/them) :nonbinary_flag: (ryanc@infosec.exchange)'s status on Wednesday, 08-Jan-2025 15:21:34 JST Ryan Castellucci (they/them) :nonbinary_flag:

     in reply to

     • John Timaeus

     @johntimaeus @gsuberland I had the main house completely gutted. Previous owner DIY'd the workshop, and the garden office is a prefab thing that for some reason has wiring with nonstandard color.