Laptop DC supplies, will anything of the right voltage and connector work?

[Infraviolet]

I need to get a spare power brick (Toshiba model PA3917U-1ACA) for a laptop, but the model (for both laptop and power brick) is old enough that new ones aren't made any more.

Fortunately the specs are very generic:

19V (I measured this to confirm, I get 19.54V at no load which seems plausible)
3.42A
11mm length, centre positive, 5.5mm outer 2.5mm inner barrel jack

So can I get any power brick with these specs and expect it to work ok, or at the very least guarantee there's no chance of it damaging the laptop.

I can find knockoff versions by unproncounceable brands on amazon which state compatibility for my laptop, but whilst they claim compatibility with the part number we all know that unrponouncable brand wall warts on amazon have a chance of being so badly built that one day they'll have a failure mode of "pump 240V mains AC straight in to your sensitive device". And powerbricks are always designed such that you've no hope of opening them up to inspect the inside before you put it in to use. I can also see proper electronics sellers (Farnell, Mouser, RS...) selling, for a somewhat higher price, power bricks for 19V 3.42A with centre positive 11mm 5.5mm, 2.5mm barrel jacks. The proper electronics sellers make no compatibility mentions but the specs seem identical.

Will anything of the right connector, voltage and current rating (or even a slightly higher current rating if that were all that was available) do the job? 65W (19V, 3.42A = 65W is clearly a very common standard for power bricks) do the job, or does the mention of compatibility on the amazon listed ones suggest they have some advantageous property which the (probably better built) proper sellers one's lack.

Thanks

[Gyro]

I would avoid Amazon like a bad smell. The unpronounceable name ones will be matched by minimal, dodgy or outright dangerous internals.

You may well find something decent, at a cost, on RS / Farnell, but you won't find direct original spec compatibility for EMC etc.

Have you looked on ebay? The important part is to avoid anything that says "For" like the plague as they will be the same quality as the Amazon ones. You will find genuine ones for little money though [EDIT: I just copied and pasted your model number] - of course the magic word is "Genuine" combined with careful comparison with the label in the listing photos and the one you have. I noticed one seller with a bunch of genuine office clearance ones for very little money and free UK delivery, but there are several others too.

Personally I much prefer second-hand genuine adapters to any dodgy cheap import or component distributor other brand one (with all the questions about connector compatibility). Big names like Toshiba don't / didn't skimp on specification and quality control and they normally age very gracefully.

[Nominal Animal]

So can I get any power brick with these specs and expect it to work ok, or at the very least guarantee there's no chance of it damaging the laptop.

Ripple and regulation *could* be an issue.  If there isn't too much ripple and the regulation is sufficient, it will work.

For example, MicroBattery/CoreParts MBA1006 is a valid replacement for PA3917U-1ACA (and for various manufacturers' chargers: 180676-001, F1781A, 722970-001, 603284-001, 700393-001, 25.L180G.001, FSP065-10AABA, PA3917U-1ACA, FRU54Y8848, 54Y8848, 0A001-00043600, FSP065-REB, NUC BOXNUC7I3BNK), per a reputable Finnish store (that no longer sells it).  It looks like in the UK, at least NetworkIntegrators sells these for £14, but do your own search.  You will likely need to get an UK C3 mains cable separately, though, as this one comes with the EU (CEE 7/7 to C3) cable.

[Infraviolet]

I've found a lot of sellers selling
"Delta Electronics ADP-65JH HB"
as a PA3917U-1ACA replacement

The brand is Taiwanese not Chinese and Delta Electronics was apparently the company which manufactured some of the original PA3917U for Toshiba. I'm finding an Amazon storefront by a UK company which also has its own website. https://www.amazon.co.uk/gp/product/B00FGVCIGW/ Assuming there aren't chinese companies outright faking the Delta Electronics name does this look a good bet?

[Andy Chee]

Whenever I go past my local e-waste drop off point, I always take a quick poke around for these larger 19V 4A bricks.  I seem to have amassed quite a collection now!

[Whales]

Yes what you want to do should work fine, I've done it for a few laptops before.

I recommend getting a used OEM laptop brick (any brand as long as its about 19V and supplies enough current).  The quality will be much better than a cheap generic.

Some laptops have 3 wire plugs (+, - and signal) and won't work with just power.  Pre-USB C thinkpads had a simple protocol (a resistor on the data line was enough).  Dells were more annoying with a digital protocol handshake before charging would start, despite it looking like a round barrel connector.

The exact voltage doesn't need to be precise.  Anything from 18V to 20V will go unnoticed.  The laptop bucks this down to whatever battery voltage it's using (highest I've seen is 3S ~= 12.6V, but there might be 4S ~= 16.8V laptops).

If the current rating on the brick is too low then its over-current protection might trip.  This can be observed as the brick turning itself off.

[coromonadalix]

some lappy  wont just accept voltages,

chargers / adapters have an id chip on the line  say 65 90 120 watt  etc ... some wont even charge  if they don't see this id

Some DELL Lenovo Hp  have this trick ...

on my side i was lucky with oem ones from china, never heated or blown ... 

bought many on Ebay, and i had the possibility to be refunded if they where not up to the task

[Infraviolet]

This is a bit of an old thread now, but briefly coming back to it...
Well I got an adapter of the right voltage from Amazon, and bought another of the same voltage from Farnell (I needed two anyway).

Both give approximately 19V output (under no load the farnell one gives like 19.7 and the amazon one 19.2, the original gave about 19.5), and the DC barrel plug, though slightly shorter (on both the Amazon and Farnell ones than for the true original part) than on the true Toshiba part, fits the laptops' sockets well. Very conveniently the DC barrel plug is the standard 5.5mm outer with 2.1/2.5mm spring-loaded inner.

I also checked both power adapters with the oscilloscope, checked the output voltage (under no load admittedly) during switch on to make sure there were no surprise spikes, and looked at the amount of ripple on the voltage of either (<50mV on both, Farnell one with a ripple slightly smaller on the o-scope's screen and a longer period to it).

They power the laptops without visible issue, Linux doesn't show me detailed diagnostics about AC input the way it can about battery state though.

One thing I do notice is both the Amazon and Farnell ones are powered by 3 pin cables (including earth) whereas the original is a two pin cable figure 8 (plastic earth on UK plug). I guess with the new ones then I'll have to be more careful any time I use my (grounded as scope's pretty much always are) oscilloscope to probe something connected to a circuit powered off a laptop's USB port (arduino like devboards and such), making sure the scope's ground is only ever put at the USB circuit's ground and never at something like the 5V line of a USB port.

I assume there's nothing else compatibility wise which could posssibly need testing before considering both adapters good for long term use?

I wouldn't, for most bought equipment, ever consider this level of detail of checking that everything is right, but I want to be able to make long term use of the laptops (albeit not as daily drivers) and they were picked for being a very specific laptop model which, since I bought them (no mains adapters included), is no longer on sale anywhere, so I'd much rather there was zero chance of their mains adapter's somehow messing them up.
Thanks

[Whales]

I assume your ripple measurements were under no-load?  Loaded measurements would be good (but of course quite difficult, you'll probably have to have the laptop open to access somewhere to probe).

Ideally you would crack open the power supply to look inside, but that's a one way trip for laptop bricks.  Just weight comparisons would be a good start, make sure one of them isn't suspiciously lighter.  Lighter = less heatsinks and caps = less lifetime.