High-voltage ntb PSU

[Behemot]

I have the older NX5000 laptop which uses 18,5 V input power, however the new power supplies are for 19 V. On the other hand since battery fluctuates between some 14,5 and 16,5 V, I would say all the internal VRMs are quite flexible.

So, do you think it will work with half a volt higher input voltage?

[mariushm]

Re: High-voltage ntb PSU

I say it will work. But the brick will probably output around 19.2v at low loads.

Alternatively, I think you could just wire a diode on the cable - these generally have voltage drop of 0.6-0.8 volts. Just pick one that can handle the amps.

[selldoor]

Re: High-voltage ntb PSU

Hi - do you have access to Amazon.com in Czech republic?

Can you get a Universal adapter
http://www.amazon.com/Universal-Adap...5521193&sr=1-2

or perhaps less postage from Germany

http://www.amazon.de/Universal-Noteb...522168&sr=1-23

[mariushm]

Re: High-voltage ntb PSU

I don't really recommend those with variable voltage output, at least those cheap ones.
They overheat a lot and can probably barely handle 50 watts...

If it's Compaq NX5000, the specs say it's a 65w adapter so you should get at least one that does that much.

Amazon lists a lot just by searching for nx5000 but they're all noname or oem compatible, not sure about their quality:

http://www.amazon.com/s/ref=nb_sb_no...nx5000&x=0&y=0

Since you're Czech, you may have better luck using amazon.co.uk or amazon.de instead of the .com version

[Behemot]

Re: High-voltage ntb PSU

The laptop itself consumes some 40 watts top (I have undervolted CPU, but this is even when charging), actuall measured value before PSU. Consider even the effectivity.

I don't need it so much to buy a new, it was more like a question of interest. Jsut thought it shoudl handle that, as I said, VRMs have to be flexible down, so there may be also flexible up. But this 0,5 V is less than 3 % difference so I wil try it and see. I took one 19V unit home as a spare so I will do it when I come home next time. Have to also buy cinch connector since I modified the cables

[Th3_uN1Qu3]

Re: High-voltage ntb PSU

The MOSFETs are 30v anyway - it'll work with up to 24 volts just fine. Tested myself.

[Behemot]

Re: High-voltage ntb PSU

uN1Qu3 saves the day again. Thanks bro

[Th3_uN1Qu3]

Re: High-voltage ntb PSU

Well that wasn't too hard, i'm sure you could have figured it out by yourself. You have to consider that the chargers can be half a volt (or even more) off from the factory, AND that regulation can't possibly be perfect (it's actually worse than in desktop PC power supplies), and it quickly becomes apparent that there has to be several volts of headroom in the electronics.

I suspect that the reason for those funny ratings is that they tested and picked the input voltage which gives highest efficiency - so they can skimp on the power bricks as much as they can. Using a lower than needed voltage will usually make the charging circuit drop out but the laptop will still run if it's not too far off. Using a higher voltage won't do any harm unless you exceed the rating of the MOSFETs - and this is always 30 volts, unless the thing is spec'd to run off 12v, in which case they might be 25v.

[Behemot]

Re: High-voltage ntb PSU

Well sure I know there is much headroom down, for the batteries. But I needed to confirm there is also headroom up

[b700029]

Re: High-voltage ntb PSU

You can confirm this by looking at the schematic:

There's a MAX1772 that charges the battery and that can handle up to 28V, and the caps are 25V, but the MAX1999 main PSU controller is rated for 24V.

So don't go beyond that. I personally would stay with 20V for a safe limit.

[Scenic]

Re: High-voltage ntb PSU

19V 3.42A (65W) or 4.74A (90W) laptop PSUs are available like sand on the beach.
Get a delta one (for example SADP-65KB) and you won't have problems (if it's an original and not a chinese knockoff)

[Behemot]

Re: High-voltage ntb PSU

Yeah I know I have a few of these 19V PSUs. That is the all reason why I asked, because original 18,5V units are difficult to find :-)