My friend has lost the power supply to her IBM Thinkpad T43.

The bottom of the laptop says we need power of 16v and 4.5 amps.

I have an old HP Pavillion power supply which fits the connector but the
power is 18.5v and 4.9amps.

Would it do any damage if I try this alternative power supply?

Ray wrote on Mon, 24 Nov 2008 19:53:36 GMT:
> My friend has lost the power supply to her IBM Thinkpad T43.
>
> The bottom of the laptop says we need power of 16v and 4.5 amps.
>
> I have an old HP Pavillion power supply which fits the connector but the
> power is 18.5v and 4.9amps.
>
> Would it do any damage if I try this alternative power supply?

That is a bit too high for my tastes. And it could be dangerous to use
it. And is the polarity correct? If not, this usually does a lot of
damage. Although if you were going to use it anyway, I would throw three
rectifier diodes in series with one of the lines. This will knock the
voltage down by 2.1 volts.

--
Bill
Asus EEE PC 8GB 1GB SoDIMM Adata 16GB
Windows XP SP2 and Xandros Linux

BillW50 wrote:

> When I got my BSEE in '76, mine was the last class that included tube
> theory. Kind of sad to see it not taught anymore. As I though it did
> well as a base to move on to solid state. :)
>

Tubes (or valves to us English), are still used to this day, and
probably will be for the forseable future. Getting a couple kW from
semiconductors is no mean feat, but can be done. Getting a couple of MW
from semiconductors is simply not possible, but tubes can manage it on a
continuous basis.

BillW50 wrote:

Although if you were going to use it anyway, I would throw three
> rectifier diodes in series with one of the lines. This will knock the
> voltage down by 2.1 volts.
>
I wouldn't do that. The diodes will get rather hot if the machine is
pulling a lot of current - and the failure mode of high current
rectifiers is often to short themselves. Then you leave with the
original problem - running too high a voltage, which will not be kind to
the laptop.

Put a wanted request out on FreeCycle. There are a lot of AC adaptors
people keep in storage after their old laptop breaks, gets lost, run
over by the 4WD, etc...

--
Adrian C

The unknown warrior wrote on Fri, 28 Nov 2008 11:38:32 +0000:
> BillW50 wrote:
>
>> When I got my BSEE in '76, mine was the last class that included tube
>> theory. Kind of sad to see it not taught anymore. As I though it did
>> well as a base to move on to solid state. :)
>
> Tubes (or valves to us English), are still used to this day, and
> probably will be for the forseable future. Getting a couple kW from
> semiconductors is no mean feat, but can be done. Getting a couple of MW
> from semiconductors is simply not possible, but tubes can manage it on a
> continuous basis.

Yes this is so true. And I thought everybody except Americans used
valves? And the device that most people have in their homes that still
has a valve (aka tube) is a microwave. I believe it is called a klystron
tube (aka valve).

--
Bill
Asus EEE PC 8GB 1GB SoDIMM Adata 16GB
Windows XP SP2 and Xandros Linux

Adrian C wrote on Mon, 24 Nov 2008 23:20:59 +0000:
> BillW50 wrote:
>
> Although if you were going to use it anyway, I would throw three
>> rectifier diodes in series with one of the lines. This will knock the
>> voltage down by 2.1 volts.
>>
> I wouldn't do that. The diodes will get rather hot if the machine is
> pulling a lot of current - and the failure mode of high current
> rectifiers is often to short themselves. Then you leave with the
> original problem - running too high a voltage, which will not be kind to
> the laptop.
>
> Put a wanted request out on FreeCycle. There are a lot of AC adaptors
> people keep in storage after their old laptop breaks, gets lost, run
> over by the 4WD, etc...

Interesting, I've done it all of the time without any ill effects at
all. You need to purchase diodes with a tolerance 30% higher than you
need. And you shouldn't have any problems whatsoever. That is what they
told me when I was getting my electronic engineering degree. And it has
worked in my decades of experience as well.

--
Bill
Asus EEE PC 8GB 1GB SoDIMM Adata 16GB
Windows XP SP2 and Xandros Linux

"BillW50" <BillW50@aol.kom> wrote in message
news:ggfdme$rfq$1@nntp.motzarella.org...
> Adrian C wrote on Mon, 24 Nov 2008 23:20:59 +0000:
>> BillW50 wrote:
>>
>> Although if you were going to use it anyway, I would throw three
>>> rectifier diodes in series with one of the lines. This will knock the
>>> voltage down by 2.1 volts.
>>>
>> I wouldn't do that. The diodes will get rather hot if the machine is
>> pulling a lot of current - and the failure mode of high current
>> rectifiers is often to short themselves. Then you leave with the original
>> problem - running too high a voltage, which will not be kind to the
>> laptop.
>>
>> Put a wanted request out on FreeCycle. There are a lot of AC adaptors
>> people keep in storage after their old laptop breaks, gets lost, run over
>> by the 4WD, etc...
>
> Interesting, I've done it all of the time without any ill effects at all.
> You need to purchase diodes with a tolerance 30% higher than you need. And
> you shouldn't have any problems whatsoever. That is what they told me when
> I was getting my electronic engineering degree. And it has worked in my
> decades of experience as well.
>
> --
> Bill
> Asus EEE PC 8GB 1GB SoDIMM Adata 16GB
> Windows XP SP2 and Xandros Linux

Wow, that must have been a shocker at your graduation. I would have thought
they would have wished you good luck instead of telling you "throw three
rectifier diodes in series with one of the lines. This will knock the
voltage down by 2.1 volts.

"BillW50" <BillW50@aol.kom> wrote in message
news:gguhe2$pvj$1@news.motzarella.org...
> The unknown warrior wrote on Fri, 28 Nov 2008 11:38:32 +0000:
>> BillW50 wrote:
>>
>>> When I got my BSEE in '76, mine was the last class that included tube
>>> theory. Kind of sad to see it not taught anymore. As I though it did
>>> well as a base to move on to solid state. :)
>>
>> Tubes (or valves to us English), are still used to this day, and probably
>> will be for the forseable future. Getting a couple kW from semiconductors
>> is no mean feat, but can be done. Getting a couple of MW from
>> semiconductors is simply not possible, but tubes can manage it on a
>> continuous basis.
>
> Yes this is so true. And I thought everybody except Americans used valves?
> And the device that most people have in their homes that still has a valve
> (aka tube) is a microwave. I believe it is called a klystron tube (aka
> valve).
>

You believe wrong. It is a magnetron.

"Adrian C" <email@here.invalid> wrote in message
news:6p0r6tF5tvg0U1@mid.individual.net...
> BillW50 wrote:
>
> Although if you were going to use it anyway, I would throw three
>> rectifier diodes in series with one of the lines. This will knock the
>> voltage down by 2.1 volts.
>>
> I wouldn't do that. The diodes will get rather hot if the machine is
> pulling a lot of current - and the failure mode of high current rectifiers
> is often to short themselves. Then you leave with the original problem -
> running too high a voltage, which will not be kind to the laptop.
>
I have never known any silicon recitifier diode to fail short circuit (but
that doesn't mean that it's impossible). I have known many that have failed
open circuit.

"Jerry" <Hello@spammers.com> wrote in message
news:ggg0cm$8f2$1@news.motzarella.org...
> "BillW50" <BillW50@aol.kom> wrote in message
> news:ggfdme$rfq$1@nntp.motzarella.org...
>> Adrian C wrote on Mon, 24 Nov 2008 23:20:59 +0000:
>>> BillW50 wrote:
>>>
>>> Although if you were going to use it anyway, I would throw three
>>>> rectifier diodes in series with one of the lines. This will knock the
>>>> voltage down by 2.1 volts.
>>>>
>>> I wouldn't do that. The diodes will get rather hot if the machine is
>>> pulling a lot of current - and the failure mode of high current
>>> rectifiers is often to short themselves. Then you leave with the
>>> original problem - running too high a voltage, which will not be kind to
>>> the laptop.
>>>
>>> Put a wanted request out on FreeCycle. There are a lot of AC adaptors
>>> people keep in storage after their old laptop breaks, gets lost, run
>>> over by the 4WD, etc...
>>
>> Interesting, I've done it all of the time without any ill effects at all.
>> You need to purchase diodes with a tolerance 30% higher than you need.
>> And you shouldn't have any problems whatsoever. That is what they told me
>> when I was getting my electronic engineering degree. And it has worked in
>> my decades of experience as well.
>>
>> --
>> Bill
>> Asus EEE PC 8GB 1GB SoDIMM Adata 16GB
>> Windows XP SP2 and Xandros Linux
>
> Wow, that must have been a shocker at your graduation. I would have
> thought they would have wished you good luck instead of telling you "throw
> three
> rectifier diodes in series with one of the lines. This will knock the
> voltage down by 2.1 volts.
>

Actually, using diodes to drop a voltage by small amounts is a good way of
doing it as the volt drop across the diode is fairly constant over a wide
current range.

M.I.5¾ wrote:
> "Adrian C" <email@here.invalid> wrote in message
>> I wouldn't do that. The diodes will get rather hot if the machine is
>> pulling a lot of current - and the failure mode of high current rectifiers
>> is often to short themselves. Then you leave with the original problem -
>> running too high a voltage, which will not be kind to the laptop.
>>
> I have never known any silicon recitifier diode to fail short circuit (but
> that doesn't mean that it's impossible). I have known many that have failed
> open circuit.

Going open circuit is the final stage, it's what happens before that ;-)

Take a look at the 3rd post.
http://www.physicsforums.com/showthread.php?t=126790

Though the heavier current diodes are more likely to stay short circuit,
this is often found in places like automotive electrics.

At lower currents yes, I'd use diode voltage drops to get an adjustment
if I needed that. But Laptop power supplies are a different beast, and
the current that flows charging a dead battery needs care in handling -
I'm always concerned choosing the right manufacturer's specified DC jack
when replacing broken parts on laptop motherboards for instance.

--
Adrian C

"M.I.5¾" <no.one@no.where.NO_SPAM.co.uk> wrote in message
news:492bee86$1_1@glkas0286.greenlnk.net...
>
>>
> I have never known any silicon recitifier diode to fail short
> circuit (but that doesn't mean that it's impossible). I have known
> many that have failed open circuit.
Well, its clear that you have never worked in the domestic electronics
servicing industry then!

"Adrian C" <email@here.invalid> wrote in message
news:6p2cjmF5tsc7U1@mid.individual.net...
> M.I.5¾ wrote:
>> "Adrian C" <email@here.invalid> wrote in message
>>> I wouldn't do that. The diodes will get rather hot if the machine is
>>> pulling a lot of current - and the failure mode of high current
>>> rectifiers is often to short themselves. Then you leave with the
>>> original problem - running too high a voltage, which will not be kind to
>>> the laptop.
>>>
>> I have never known any silicon recitifier diode to fail short circuit
>> (but that doesn't mean that it's impossible). I have known many that
>> have failed open circuit.
>
> Going open circuit is the final stage, it's what happens before that ;-)
>
> Take a look at the 3rd post.
> http://www.physicsforums.com/showthread.php?t=126790
>
> Though the heavier current diodes are more likely to stay short circuit,
> this is often found in places like automotive electrics.
>

I have only encountered the heavier current diodes in relatively high energy
circuits such as power supplies (though we do use them as steering diodes in
aircraft DC power circuits)

"Roy.Livingstone" <Roy.Livingstone@baesystems.com> wrote in message
news:492bfbec$1_1@glkas0286.greenlnk.net...
>
> "M.I.5¾" <no.one@no.where.NO_SPAM.co.uk> wrote in message
> news:492bee86$1_1@glkas0286.greenlnk.net...
>>
>>>
>> I have never known any silicon recitifier diode to fail short circuit
>> (but that doesn't mean that it's impossible). I have known many that
>> have failed open circuit.
> Well, its clear that you have never worked in the domestic electronics
> servicing industry then!
Actually I have but it was many many years ago but I do get to dabble when
something goes wrong at home. But my main area these days is airborne
electrical and electronic systems and ground support systems. Something you
may care to bear in mind next time you board an aircraft to fly on holiday.
:-/

I also worked from the manufacturing (design) end and I had a hand in a
large part of the colour processing circuitry of the original VCR system
video recorder.

On Tue, 25 Nov 2008, M.I.5¾ wrote:

>
"Jerry" <Hello@spammers.com> wrote in message
> news:ggg0cm$8f2$1@news.motzarella.org...
>> "BillW50" <BillW50@aol.kom> wrote in message
>> news:ggfdme$rfq$1@nntp.motzarella.org...
>>> Adrian C wrote on Mon, 24 Nov 2008 23:20:59 +0000:
>>>> BillW50 wrote:
>>>>
>>>> Although if you were going to use it anyway, I would throw three
>>>>> rectifier diodes in series with one of the lines. This will knock the
>>>>> voltage down by 2.1 volts.
>>>>>
>>>> I wouldn't do that. The diodes will get rather hot if the machine is
>>>> pulling a lot of current - and the failure mode of high current
>>>> rectifiers is often to short themselves. Then you leave with the
>>>> original problem - running too high a voltage, which will not be kind to
>>>> the laptop.
>>>>
>>>> Put a wanted request out on FreeCycle. There are a lot of AC adaptors
>>>> people keep in storage after their old laptop breaks, gets lost, run
>>>> over by the 4WD, etc...
>>>
>>> Interesting, I've done it all of the time without any ill effects at all.
>>> You need to purchase diodes with a tolerance 30% higher than you need.
>>> And you shouldn't have any problems whatsoever. That is what they told me
>>> when I was getting my electronic engineering degree. And it has worked in
>>> my decades of experience as well.
>>>
>>> --
>>> Bill
>>> Asus EEE PC 8GB 1GB SoDIMM Adata 16GB
>>> Windows XP SP2 and Xandros Linux
>>
>> Wow, that must have been a shocker at your graduation. I would have
>> thought they would have wished you good luck instead of telling you "throw
>> three
>> rectifier diodes in series with one of the lines. This will knock the
>> voltage down by 2.1 volts.
>>
>
> Actually, using diodes to drop a voltage by small amounts is a good way of
> doing it as the volt drop across the diode is fairly constant over a wide
> current range.
>
It's hardly a novel trick, it's been done enough times. Indeed, one
reason you see so many diodes in the schematics of what's inside
integrated circuits is because the scheme is used to drop voltage,
diodes using up less space on the chip than resistors.

Michael