> On 2013-06-25, Mr. Man-wai Chang <toylet.toylet@gmail.com> wrote:
>> On 25/06/2013 8:01 PM, John G wrote:
>>> NO!
>>> Shorted is the correct description.
>>> They are both referenced to ground so MAGIC SMOKE will result. :-?
>>
>> OTOH, should I attempt -5V and +12V pins at the power connector? Or
>> should I try +5V and -12V?
>>
>> Which one is safer and could supplies 4A?
>
> neither, both -5 and -12 are typically capable of less than 1A (0.2A
> on a device at hand)
>
> -5 has been discontinued in new PCs
>
> If you need 17V and 4A you could try an aftermarket adjustable laptop
> power brick, It might be easier to find one at 18V or 16V though, but
> there are 17V ones out there.
>
Which I find all the time in the garbage. Or that time I needed a power
supply for a Powerbook 1400, I opened up an inkjet printer I'd dragged
home from the garbage, and it had the right voltage (those tend to have
higher voltages than +12, but still decent current). The external power
supplies have the advantage that they are already cased. The inkjet
supplied a standalone power supply board, making it easy to extract, but
not casing.
But, the problem is that applying voltage to a battery isn't a good thing,
if the battery is some more recent kind, it needs a proper charger.
Michael
Reply by Jasen Betts●June 27, 20132013-06-27
On 2013-06-25, Mr. Man-wai Chang <toylet.toylet@gmail.com> wrote:
> On 25/06/2013 8:01 PM, John G wrote:
>> NO!
>> Shorted is the correct description.
>> They are both referenced to ground so MAGIC SMOKE will result. :-?
>
> OTOH, should I attempt -5V and +12V pins at the power connector? Or
> should I try +5V and -12V?
>
> Which one is safer and could supplies 4A?
neither, both -5 and -12 are typically capable of less than 1A (0.2A
on a device at hand)
-5 has been discontinued in new PCs
If you need 17V and 4A you could try an aftermarket adjustable laptop
power brick, It might be easier to find one at 18V or 16V though, but
there are 17V ones out there.
--
⚂⚃ 100% natural
--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Reply by JW●June 26, 20132013-06-26
On Tue, 25 Jun 2013 12:17:35 -0400 "P E Schoen" <paul@peschoen.com> wrote
in Message id: <kqcfh9$qon$1@dont-email.me>:
>Usually the +5V and +12V supplies are fairly high current. And in many cases
>only the +5V supply is directly regulated. It might be possible to reverse
>the diodes and output capacitor on the +12V supply to make it -12V, and then
>you should get 17V between them.
IF it's possible, and I have a feeling that it's not, you'd better flip
the polarity on the electrolytic caps as well!
Reply by Mr. Man-wai Chang●June 26, 20132013-06-26
Guess this project is too dangerous for a beginner! Thank you all! :)
--
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^ ^ 12:30:01 up 21:59 0 users load average: 0.04 0.04 0.05
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
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Reply by Jamie●June 25, 20132013-06-25
Mr. Man-wai Chang wrote:
>
> 1. If I shorted the +5V and +12V in the molex connector,
> would I get +17V? What's the max. current?
>
> 2. Could I use 17V to charge a notebook battery rated 16V and 3.8A?
> Would it hurt the battery?
>
No
Jamie
Reply by Michael A. Terrell●June 25, 20132013-06-25
Michael Black wrote:
>
> On Tue, 25 Jun 2013, Ian Field wrote:
>
> >
> >
> > "Michael Black" <et472@ncf.ca> wrote in message
> > news:alpine.LNX.2.02.1306251532390.5374@darkstar.example.org...
> >> On Tue, 25 Jun 2013, Mr. Man-wai Chang wrote:
> >>
> >>> On 25/06/2013 8:01 PM, John G wrote:
> >>>> NO!
> >>>> Shorted is the correct description.
> >>>> They are both referenced to ground so MAGIC SMOKE will result. :-?
> >>>
> >>> OTOH, should I attempt -5V and +12V pins at the power connector? Or should
> >>> I try +5V and -12V?
> >>>
> >> The minus supplies, if they are even still there, have minimal current,
> >> were way in the beginning because RAM might have needed some negative
> >> voltage (I can't remember if those RAM were still in existence in 1981
> >
> > The original 5150 PC had provision for 3 rail RAM, selected by the
> > configuration DIP switches.
> >
> > I have yet to aquire a 5150 board that hadn't been fucked up by someone
> > messing with the DIP switches!
> >
> I'd forgotten about the dip switches on those.
>
> But how many were actually shipped with low density RAM? I thought it was
> the 4K RAM that needed negative voltage, and I thought by the time the
> IBM came out, it would use 64K RAM, which I thought did away with the need
> for negative voltage.
The early PC motherboards were shipped with four banks of 16K RAM.
Reply by ●June 25, 20132013-06-25
On Tue, 25 Jun 2013, Ian Field wrote:
>
>
> "Michael Black" <et472@ncf.ca> wrote in message
> news:alpine.LNX.2.02.1306251532390.5374@darkstar.example.org...
>> On Tue, 25 Jun 2013, Mr. Man-wai Chang wrote:
>>
>>> On 25/06/2013 8:01 PM, John G wrote:
>>>> NO!
>>>> Shorted is the correct description.
>>>> They are both referenced to ground so MAGIC SMOKE will result. :-?
>>>
>>> OTOH, should I attempt -5V and +12V pins at the power connector? Or should
>>> I try +5V and -12V?
>>>
>> The minus supplies, if they are even still there, have minimal current,
>> were way in the beginning because RAM might have needed some negative
>> voltage (I can't remember if those RAM were still in existence in 1981
>
> The original 5150 PC had provision for 3 rail RAM, selected by the
> configuration DIP switches.
>
> I have yet to aquire a 5150 board that hadn't been fucked up by someone
> messing with the DIP switches!
>
I'd forgotten about the dip switches on those.
But how many were actually shipped with low density RAM? I thought it was
the 4K RAM that needed negative voltage, and I thought by the time the
IBM came out, it would use 64K RAM, which I thought did away with the need
for negative voltage.
Michael
Reply by Ian Field●June 25, 20132013-06-25
"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1306251529490.5374@darkstar.example.org...
> On Tue, 25 Jun 2013, Mr. Man-wai Chang wrote:
>
>>
>> 1. If I shorted the +5V and +12V in the molex connector,
>> would I get +17V? What's the max. current?
>>
> No, because probably one side of each is already grounded inside the pwoer
> supply.
>
>> 2. Could I use 17V to charge a notebook battery rated 16V and 3.8A?
>> Would it hurt the battery?
>>
> NO, because these likely are fancy batteries and you don't just push
> current through them, it has to be controlled based on the state of the
> battery.
If its a lithium battery - charging with anything other than properly
designed circuitry can be very dangerous!
Reply by Ian Field●June 25, 20132013-06-25
"P E Schoen" <paul@peschoen.com> wrote in message
news:kqcl62$rtn$1@dont-email.me...
In the UK; Maplin sells a universal laptop PSU with a voltage selector
switch and an assortment of power jack attachments.
This device depends on the laptop having its own internal charging circuit,
its not intended for charging any battery directly.
Most developed countries probably have a better choice than our just Maplin.
Reply by Ian Field●June 25, 20132013-06-25
"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1306251532390.5374@darkstar.example.org...
> On Tue, 25 Jun 2013, Mr. Man-wai Chang wrote:
>
>> On 25/06/2013 8:01 PM, John G wrote:
>>> NO!
>>> Shorted is the correct description.
>>> They are both referenced to ground so MAGIC SMOKE will result. :-?
>>
>> OTOH, should I attempt -5V and +12V pins at the power connector? Or
>> should I try +5V and -12V?
>>
> The minus supplies, if they are even still there, have minimal current,
> were way in the beginning because RAM might have needed some negative
> voltage (I can't remember if those RAM were still in existence in 1981
The original 5150 PC had provision for 3 rail RAM, selected by the
configuration DIP switches.
I have yet to aquire a 5150 board that hadn't been fucked up by someone
messing with the DIP switches!