[Ray Thomas]

New laptop exhibits the typical poor grounding/RF hash and noise issue that
has been raised here so often, when using an Echo soundcard. Old laptop was
totally silent given same conditions, so I want to try some interchanging of
the 2 power supplies. My question is: can I do this with safety (to the
computers, no risk to myself)? Luckily both laptops need to see 19 volt DC
(centre pin + in both cases)...the only difference between them is that the
old supply is rated at 4.22 A, the new one is 3.42 A. Is this difference
significant or not ? Can I interchange them confidently ? Wouldn't you know
it..the old supply is two pin connection to mains, new one has 3 pins (ie
earthed)....guess which is the noisy one ! If this experiment fails then
ground lifting via cheater plug may be needed ? Thanks for advice,
Ray

[Mike Rivers]

On Sep 19, 5:06 am, "Ray Thomas" wrote:

Luckily both laptops need to see 19 volt DC
(centre pin + in both cases)...the only difference between them is that the
old supply is rated at 4.22 A, the new one is 3.42 A. Is this difference
significant or not ?

In that direction, no.

..the old supply is two pin connection to mains, new one has 3 pins (ie
earthed)....guess which is the noisy one ! If this experiment fails then
ground lifting via cheater plug may be needed ?

Given the large amount of plastic on a computer and the fact that the
power supply output (that goes to the computer) is already isolated
from the line by a transformer, there is no real safety issue with
lifting the safety ground pin. Try that first. If it solves your
problem, you can probably accept the risk leaving it that way. It'
unlikely that it will kill you or burn your house down. Just don't try
it with something that might actually be dangerous to you or your
electrical wiring.

If you want a more elegant solution than a fifty cent ground adapter,
you can use a $60 Ebtech Hum-X.

[Arny Krueger]

"Ray Thomas" wrote in message

New laptop exhibits the typical poor grounding/RF hash
and noise issue that has been raised here so often, when
using an Echo soundcard. Old laptop was totally silent
given same conditions, so I want to try some
interchanging of the 2 power supplies.

Probably futile, but...

My question is:
can I do this with safety (to the computers, no risk to
myself)?

Playing power supply roulette with an expensive laptop isn't high on my list
of wise moves.

OTOH I have had pretty good luck with a fairly expensive *universal* laptop
power supply. But the maker said that what I was trying to do would work,
and he's got more money on the table than I did.

Luckily both laptops need to see 19 volt DC
(centre pin + in both cases)...the only difference
between them is that the old supply is rated at 4.22 A,
the new one is 3.42 A. Is this difference significant or
not ?

YMMV. Remember that these switchmode power supplies have fairly close
current limiting. The power use of a computer varies all over the map. The
actual drain on the power supply may depend on the state of the battery. If
the battery is in good shape, you might pull it off, but no warranties
expressed or implied by the undersigned here!

Can I interchange them confidently?

Never, not even after you saw it work under a limited set of conditions.

Wouldn't you
know it..the old supply is two pin connection to mains,
new one has 3 pins (ie earthed)....guess which is the
noisy one ! If this experiment fails then ground lifting
via cheater plug may be needed ?

I'd try the cheater first, as it is less risky. However, bypassing the
grounding pin is not recommended - its a big safety hit.

Why not tell us more about your noise problem? Instead of backdooring the
problem with a risky power supply mod, maybe we can fix it by the front door
and good signal grounding practice.

[Ray Thomas]

"Soundhaspriority" wrote in message
...

"Ray Thomas" wrote in message
...
New laptop exhibits the typical poor grounding/RF hash and noise issue
that has been raised here so often, when using an Echo soundcard. Old
laptop was totally silent given same conditions, so I want to try some
interchanging of the 2 power supplies. My question is: can I do this with
safety (to the computers, no risk to myself)? Luckily both laptops need
to see 19 volt DC (centre pin + in both cases)...the only difference
between them is that the old supply is rated at 4.22 A, the new one is
3.42 A. Is this difference significant or not ? Can I interchange them
confidently ? Wouldn't you know it..the old supply is two pin connection
to mains, new one has 3 pins (ie earthed)....guess which is the noisy one
! If this experiment fails then ground lifting via cheater plug may be
needed ? Thanks for advice,
Ray
Ray,
Yes, you can do it. There is one caveat: you are removing a level of
protection with respect to battery catastrophes. However, there are so
many more redundant layers of protection in the system, don't worry about
it.

Bob Morein
(310)
237-6511 --------------------------------------------------------------------------------------------
Thank you for your advice guys, I took a deep breath and swapped the
supplies and both laptops work fine with each other's supplies.Also,
whichever laptop feeds from the non-earthed (2 pin)transformer supply is
predictably noise free, so I guess I'll do a ground pin lift on the other.
As an additional point of info, this experiment coincided with a need to use
my Echo Indigo IO soundcard with the relatively new (and to some degree
non-beta tested) DuelAdapter Cardbus to Express Card adaptor dongle. I can
report that it works just fine with that card, in my system. Looks awkward,
and there is a scary degree of 'interconnectedness' when you look at all
those socket joins, waiting for an accidental bump to send the whole
recording chain into oblivion, but it works as advertised. As with all such
new products, YMMV (but at least you get a decent money back/return warranty
with these guys)
Ray

[Richard Crowley]

"Ray Thomas" wrote ...
Thank you for your advice guys, I took a deep breath and swapped the
supplies and both laptops work fine with each other's supplies.

Note that while many people said that running a load from a
supply with a higher current rating is likely OK, using the smaller
supply with the other load is NOT NECESSARILY a good idea.
At least without knowing what kind of load is represented by the
other load.

Also, whichever laptop feeds from the non-earthed (2 pin)
transformer supply is predictably noise free, so I guess I'll
do a ground pin lift on the other.

I bought a (used) "brick" for my Dell Inspiron (on eBay) and it
had an intermittent problem right at the moulded mains power
plug. I chopped it off and replaced the 3-prong plug with an
after-market 2-prong plug to fix the intermittent problem. It
also eliminated the bad buzz/hum problem when interfacing
the audio output to an external power amp.

[Mike Rivers]

On Sep 22, 7:44 am, "Richard Crowley" wrote:

I bought a (used) "brick" for my Dell Inspiron (on eBay) and it
had an intermittent problem right at the moulded mains power
plug. I chopped it off and replaced the 3-prong plug with an
after-market 2-prong plug to fix the intermittent problem. It
also eliminated the bad buzz/hum problem when interfacing
the audio output to an external power amp.

My Dell laptop always buzzed a little but since I didn't use it for
serious audio applications I never worried about it. But the three-
conductor power cord was really bulky, and this was my traveling
computer. I cut it off at the power supply plug end, attached a piece
of 18 gauge 2-conductor zip cord with molded plug salvaged from a
discarded lamp, and it packed better. Now that this laptop is my
workshop computer and does get used for testing audio gear, having no
safety ground on the computer chassis is much appreciated.

I haven't been electrocuted yet, probably thanks in part to the safety-
grounding of anything attached to the computer that might also go to
the computer's ground point.