Help! Universal Adaptor Question

[Annie]

Hi, I just bought a portable handheld tv, the Casio TV-970, and want to
purchase a universal adaptor for it.
The universal adaptors I've seen have different ratings, from 350mA, to over
1000mA.
The specifications on the user guide says that it runs on 6 volts, and the
power consumption is approximately 3.1W.

How much mA do I need?

Regards,
Patrick

 

[mike]

Don Bruder wrote:

In article <d3so8q$hfr$1@reader01.singnet.com.sg>,
"Annie" <afritz@aol.com> wrote:


Hi, I just bought a portable handheld tv, the Casio TV-970, and want to
purchase a universal adaptor for it.
The universal adaptors I've seen have different ratings, from 350mA, to over
1000mA.
The specifications on the user guide says that it runs on 6 volts, and the
power consumption is approximately 3.1W.

How much mA do I need?

Regards,
Patrick





Watts = volts * amps, so 3.1 watts / 6 volts = 0.516 and change amps =
516 mA = round up to the next hundred to give you some "wiggle room",
and get a 6 volt, 600+ mA adapter (I'd expect that the closest
acceptable unit you'll find will be a 750 mA, although you might be able
to get your hands on a 600 mA version) and you're golden. The key is *AT
LEAST* the mA rating of the device. Anything less than the device's
rating, and you'll let all the magic smoke out of the adapter. More than
the device's rating will do no harm, but it won't do any good, either.
(beyond *MAYBE* extending the life of the adapter because it isn't
working "up against the redline" constantly.)

While you haven't said anything WRONG, that's only a small part of the
issue.
If you're talking REGULATED wall wart at 6V and battery charging is NOT
involved, you are pretty safe using anything over the minimum required.

But most wall warts are NOT REGULATED. And the worst of the bunch are
the switchable voltage ones.
The voltage printed on the label is a nominal guideline voltage at some
unspecified load conditions. Two different brands with the same numbers
on the label can have significantly different voltage output at the same
current. The voltage can be much higher at low load. So if your
adapter is rated for higher current, your nominal load
will be a smaller percentage of rated and the voltage is likely to be
higher...sometimes a LOT higher. Especially when you turn the device
off, the voltage may increase enough to damage some internal parts ahead
of the switch.

Then there's the size of the barrel connector. If it's just a little
too big, it can spring the contact so the thing won't run on batteries
any more. It's fun to go to Radio Shack and watch the "we got answers
guy" try to cram different sized connectors into the customer unit.

Your problems multiply if the adapter charges internal batteries.
Battery charging is often carefully tuned to the AC adapter
characteristics to save that last penny. An adapter that's too powerful
can severely unbalance that equation leading to smoke.

Call me paranoid, but weigh the cost of the TV against what you'll save
by not buying the vendor recommended adapter. Is the difference worth
the risk. Even if it works 99% of the time, somebody has to be the 1%.

Now, if you've got the instrumentation and are willing to test the
process over the range of conditions, you can make almost anything work.
mike

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[Chris]

Annie wrote:

Hi, I just bought a portable handheld tv, the Casio TV-970, and want
to
purchase a universal adaptor for it.
The universal adaptors I've seen have different ratings, from 350mA,
to over
1000mA.
The specifications on the user guide says that it runs on 6 volts,
and the
power consumption is approximately 3.1W.

How much mA do I need?

Regards,
Patrick

Hi, Patrick. The rule for voltage sources is that, as long as you
don't exceed their maximum current rating, providing the voltage is a
done deal. Using the power equation

P = V * I

or power equals volts times amps, you need about 0.5 amps, or 500mA.
Any adapter that provides more than 500mA should be OK.

If you're in a hurry, go to any Radio Shack and get their 6V/800mA
AC-to-DC Power Adapter, Catalog #: 273-1761 for the semi-outrageous
price of $17.99. Bring your Casio, and have the counter person pick
out the "Adaptaplug" you need.

As always at Radio Shack, you'll overpay, but that's the cost of
getting the electronics component you want on a Sunday afternoon.
Also, if you're an absolute newbie, there's a good chance the counter
person will know more than you (but ask first anyway, that's not always
the case). If you choose the wrong adapter and happen to hook it up
backwards, you'll probably let the smoke out. If you want to go with
one of those universal adapters, be sure to get one rated for more than
500mA. Also, if you've got kids (voice of experience), use epoxy to
glue the correct adapter in place and set the voltage switch on the 6V
setting. Throw the other adapters out or hide them.

Good luck
Chris

 

[Annie]

Thanks everyone, I managed to purchase a brand new, original Casio adaptor
at a
steal(80% off!), and it turns out to be about half the price of the cheapest
800mA universal adaptor available here.

Regards,
Patrick

"JANA" <jana@ca.inter.net> wrote in message
news:3chpqpF6lpdncU1@uni-berlin.de...

For your TV type, you should get in touch with Casio, and order the
original.

These sets are easily damaged, if the adaptor does not properly match for
its needs! I have seen a fair number of clients have problems after. Only
Casio can service the their sets, and the cost is not worth it.

--

JANA
_____


"Annie" <afritz@aol.com> wrote in message
news:d3so8q$hfr$1@reader01.singnet.com.sg...
Hi, I just bought a portable handheld tv, the Casio TV-970, and want to
purchase a universal adaptor for it.
The universal adaptors I've seen have different ratings, from 350mA, to
over
1000mA.
The specifications on the user guide says that it runs on 6 volts, and the
power consumption is approximately 3.1W.

How much mA do I need?

Regards,
Patrick