Akai GX-747

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I might have just done something stupid. I got ahold of the above
reel-to-reel machine to play with. It's got a foreign power plug (two
round prongs), requiring 240 VAC. Years ago, my friend had it working
on 120 VAC with an adapter, but the machine has been unused for a long
time. The adapter he used is shot, so I bought a new reverse 120 V to
240 V converter, rated at 40W. The Akai unit is rated at 140W.
Without checking the wattage ratings, I plugged the thing in, powered
it on, put a tape on and pushed the play button. The mechanism engaged
briefly, but the meter lamps got dim, and the mechanism immediately
disengaged. My concern is whether or not I might have done damage by
under-powering the unit. There were no pops or smells or bad noises.
Does anyone know if the behavior I described above could be related to
broken belts or something else?

Thanks,
Dave Corsello
www.davecorsello.com
 
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On 4 Dec 2004 20:42:19 -0800, d.corsello@att.net (Dave Corsello)
wrote:

>I might have just done something stupid. I got ahold of the above
>reel-to-reel machine to play with. It's got a foreign power plug (two
>round prongs), requiring 240 VAC. Years ago, my friend had it working
>on 120 VAC with an adapter, but the machine has been unused for a long
>time. The adapter he used is shot, so I bought a new reverse 120 V to
>240 V converter, rated at 40W. The Akai unit is rated at 140W.
>Without checking the wattage ratings, I plugged the thing in, powered
>it on, put a tape on and pushed the play button. The mechanism engaged
>briefly, but the meter lamps got dim, and the mechanism immediately
>disengaged. My concern is whether or not I might have done damage by
>under-powering the unit. There were no pops or smells or bad noises.
>Does anyone know if the behavior I described above could be related to
>broken belts or something else? <snip>

Well, considering you might have overloaded the step-up transformer by
about 100% or more, I can see why things got dim! Most Akais are
"universal" machines inside; multi-tap transformers, later models are
even switchable from the rear. Only thing to change would be the
power cord, if this is the case. I'm not sure about this particular
model. Hopefully, you have schemos.

Get the voltage right and try again. My guess is that you didn't hurt
anything in the deck, although your little plastic wall-wart thing
might be a little amorphous now. If nothing moved at all, it's
possible bearings are gooey and in need of service. But, I'd get rid
of your current limiting set-up before doing anything else.

dB
 
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Dave Corsello <d.corsello@att.net> wrote:
>I might have just done something stupid. I got ahold of the above
>reel-to-reel machine to play with. It's got a foreign power plug (two
>round prongs), requiring 240 VAC. Years ago, my friend had it working
>on 120 VAC with an adapter, but the machine has been unused for a long
>time. The adapter he used is shot, so I bought a new reverse 120 V to
>240 V converter, rated at 40W. The Akai unit is rated at 140W.
>Without checking the wattage ratings, I plugged the thing in, powered
>it on, put a tape on and pushed the play button. The mechanism engaged
>briefly, but the meter lamps got dim, and the mechanism immediately
>disengaged. My concern is whether or not I might have done damage by
>under-powering the unit. There were no pops or smells or bad noises.
>Does anyone know if the behavior I described above could be related to
>broken belts or something else?

No, but you will notice that the output voltage from the autotransformer
you are using is probably dropping down to 50V or so as soon as you
overload it.

The cost of a 150W autotransformer with good regulation, though, is going
to be more than a quarter-track consumer recorder is worth.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
 
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In article <34da5b71.0412042042.4463bcfe@posting.google.com> d.corsello@att.net writes:

> I might have just done something stupid. I got ahold of the above
> reel-to-reel machine to play with. It's got a foreign power plug (two
> round prongs), requiring 240 VAC.

> I bought a new reverse 120 V to
> 240 V converter, rated at 40W. The Akai unit is rated at 140W.

> I plugged the thing in, powered
> it on, put a tape on and pushed the play button. The mechanism engaged
> briefly, but the meter lamps got dim, and the mechanism immediately
> disengaged. My concern is whether or not I might have done damage by
> under-powering the unit.

You didn't do any damage to the recorder, but you probably ruined the
converter. YOu might want to look closely at the recorder to see if
there's a voltage switch on it. Some models have a multi-tapped power
transformer and all you need to do is select 120 V and change the
plug.

You're probably stuck with an underpowered adapter, though. Even if
you take it back to the shop where you bought it and tell them that it
doesn't work, probably the best they'll do for you is give you a new
one of the same type. The reason why these things have wattage
specified on them is so you'll know what not to use them with.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
 
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Thanks to all for the info. There is no voltage selection switch on
the outside of the unit. I did find that the foreign plug is an
adapter that fits over an ungrounded US (North American?) plug, so
maybe there's a switch inside the unit. I also learned that this
machine does contain belts. Actually, the behavior I'm seeing, except
for the dimming of the meter lamps, is very similar to what I saw when
I pulled out a 4-track cassette recorder after years of lying unused.
That machine had a broken belt. The mechanism would begin to go into
gear, but then at the point when the broken belt would have kicked in,
it disengaged. It's probably best to remove a few screws and see
what's happening inside. Thanks again for all the advice.
 
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Sure enough. I pulled the back off the unit, found the power setting,
changed it, and now the machine is working. Thank you very much!