Compaq (off topic)

From: Max Eskin <>
Date: Mon Jul 20 20:38:05 1998

The thing powers up off the keyboard, like a mac. I tried powering it
off a PC SMPSU, otherwise loaded by the PC from which it came. The
PSU was working fine, and I got correct voltages, even the right
voltages on the external power connector on the laptop (I connected
the wires to the battery terminals). And now matter how many times I
pressed the on button, the #*%^)!$ thing wouldn't start. Ideas?
>Surely you mean 170mA here. It's normal to charge at the C/10 rate, at
>least when trickle charging. And I'd give it about 14 hours to make up
>for losses in the battery (you never get the energy out that you put
>> If the 'float voltage of the battery goes over the 12v figure, that
>> cut down the charging current. The _best_ thing would be a
>> on the PS output, and a variac controlling input of the _big_ PS.
>Wait a second. I thought he was using a PC power supply. Those have
>internal regulation. Hanging one off a Variac won't do a darn thing
>from test the line regulation of the PSU.
>> Now, as to whether or not you can get away with the 'big PS' on the
>> laptop instead of the battery? If at all possible, don't try. The
>> battery is providing an imense ammount of conditioning to the
>> power flow. (There are amazing ammounts of garbage floating on top of
>> the normal PS output. [everything from 'lightning induced spikes, on
>Every regulated power supply that I have ever seen has a fair amount of
>internal filtering. Now while it's not a good idea to only load one of
>the subsiduary outputs of an SMPS (and remember that in a PC PSU, the
>output is the main one, from which the regualtor sense lines are
>I think that noise on the output would be the least of your worries.
>> down to spikes from the local refrigerator turning on].) If you
>> try, it won't hurt to throw a few thousand mfd of capacitor across
>> things. Voltage wise, you are probably O.K.
>There's probably 2200-4700uF inside the PSU across the 12V rail.
>> Chuck

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Received on Mon Jul 20 1998 - 20:38:05 BST

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