Re: [tlug] EE question (was: VPN?)

[Kalin KOZHUHAROV <me.kalin@example.com>]

On Sat, Jul 7, 2018 at 8:15 PM, David J Iannucci
<jlinux@example.com> wrote:
>> 19V x 3.42A = 65 W (well VA actually). If you use a 65W or beefier PSU
>> with around 19V, you should be fine.
>  My leftover PSU is 18.5V ⎓ 3.5A (and there's the proof that it's a DC
> PSU also :=)
>
Yep, that good enough.

>> Do a triple check that polarity is matched! If you reverse the +
>> and -, oftentimes you will let the magic smoke off (some regulator on
>> the board) and that is the end.
>
> I had always thought that polarity wasn't very important, so I'm glad
> you corrected that notion for me. The PSU is marked for polarity, as
> usual, but the PC is not. How can I check without risking it? I found a
> manuf. spec sheet but this sort of info is not given. These things are
> almost always + in the center, right? That's what the PSU is.
>
Well, yes, 99% statistically looking. But it is enough for your
particular PC to be in the 1% :-)
If you have a DMM, any ohmmeter or connectivity checker, try to see
which side is connected to the metal part of the PC (e.g. MB bolt).
If neither or both are... you are out of luck, try your chance.
Otherwise, I can bet 1000:1 that the connected one is "-".

>> I think it is safe (for me at least, LoL) for you to try. Check the
>> temperature (by hand) on the PSU, load the machine (cpuburn, build a
>> kernel with -j8, `john --test`, etc.) for an hour and check the
>> temperature every few minutes initially.
>
> So I guess if it doesn't die within the first few minutes, and can run
> hard without the PSU getting warm, then I'm good, eh?
>
Warm is OK under load, but not hot. You should be comfortable holding
it in bare hand for a minute.

Cheers,
Kalin.