Brother PT-1750 P-Touch and its AC adapter

[Paul]

I figured I'd post this here, as I don't know of a place
where this would be more on topic. I wasted a few bucks
figuring this out, so some other people might benefit
from my bad luck.

I picked up a Brother PT-1750 label maker. It takes
six AA batteries (9 volts worth). When I got to the cash
with my purchase, the cashier said it has an optional adapter,
something I wasn't expecting to have to purchase. I took a
pass on the official adapter and headed to Radio Shack.

The Brother has printed in the manual and on the side of the
chassis, that is uses 7V 1.2 amps for the adapter. I bought
a 7V 2.1 amp adapter from Radio Shack (the extra current
capacity means it can easily handle a 1.2 amp load). It didn't
work. The display lit up but after two seconds, the unit switched
off.

So, I ended up buying the official AD-30 7V 1.2Amp adapter,
for $40 Canadian. I took it home and got out my voltmeter.
With no load, the adapter puts out 9.4 volts. What this means
is, the adapter is an old style _unregulated_ adapter. When
zero current is flowing, it puts out 9.4 volts (roughly the
same voltage as the batteries would). When you draw 1.2 amps,
it puts out 7 volts. Almost all Radio Shack adapters now, are
tightly regulated. My 7V Radio Shack adapter puts out 7.03 volts
at no load and also when drawing 1.55 amps.

So, what happens is, the P-Touch checks to see if the adapter
provides 9V before starting up the heavy current consuming
parts of the unit. My Radio Shack purchase looked "weak" to it,
so it didn't start.

While I haven't done this experiment, you might also have better
luck if you connect a 9VDC regulated supply to the unit, because
at least then it will stay powered on. The 9VDC regulated supply
would look exactly like a set of batteries.

Hope this helps somebody, and saves them buying the wrong adapter.

Paul

 

[Herbert Nagler]

Sorry to hear about your experience.
I have a P-Touch 2420 PC sitting next to my desktop and I absolutely love it
( no batteries). Reading about your trouble, I examined my Brother adaptor,
which came with it (A40914A - Output 9.5VDC, 1.4A). Looking at the pinout
diagram, it suggests, that the centre pin is negative (unusual). I just
wonder, if your Radio Shack adaptor is centre pin positive. That would be an
honest mistake to make, because most appliances of this kind nowadays have a
positive.ctr.pin. Maybe you can return it, if that's the case.
Just a thought.....but thanks for your info, tell us how you went.

Good luck
H.N.

 

[Paul]

Sorry to hear about your experience.
I have a P-Touch 2420 PC sitting next to my desktop and I absolutely love it
( no batteries). Reading about your trouble, I examined my Brother adaptor,
which came with it (A40914A - Output 9.5VDC, 1.4A). Looking at the pinout
diagram, it suggests, that the centre pin is negative (unusual). I just
wonder, if your Radio Shack adaptor is centre pin positive. That would be an
honest mistake to make, because most appliances of this kind nowadays have a
positive.ctr.pin. Maybe you can return it, if that's the case.
Just a thought.....but thanks for your info, tell us how you went.

Good luck
H.N.
------------------------------

I'm careful about stuff like that. You have to rotate the adaptaplug 180
degrees and plug it in, to get negative center. I check with a meter before
plugging something like that in, as a mistake would lead to instant
destruction. The P-Touch still works, it just cost me more to get it
there than I would have liked. If Brother had printed 9V 1.2A on the side
of the chassis, I wouldn't be posting here right now.

Paul