As you yourself said, the C128 logic board requires 9vac. But why
is this cheap one harmful for electronics?
>>
>>
>> I looked in Radio Shack, at some step-down transformers for
'traveling
>> abroad'. There is a price range, with some 'for heating appliances
>> only' (the cheapest) and the higher priced ones allow motors, and
>> the $34 ones allow electronic devices. What is the difference among
>> these units? Also, could a transformer such as in these theoretically
>> be reversed and used for step-up purposes?
>
>The very cheap one ('for heating appliances only') is probably a triac
>circuit. Like a lamp dimmer fixed at half-brightness. And that one
can't
>step up, of course. Don't use that for anything but heaters/lamps. I've
>seen the result of plugging a Mac+ into one of those, and it wasn't
>pretty. It took me a long time to rebuild the analgoue board. If the
>owner had asked me what to do in the first place, I'd have simply cut
the
>link...
>
>The true transformers can be used as a step-up unit. But owing to
losses,
>etc, you may not get the output voltage that you expect (it will, in
>general, be lower than you'd expect). But it should work.
>
>You may find it's cheaper to buy a bare transformer and add the
>case/connectors yourself.
>
>BTW, another trick which I hesitate to mention because it can casue
>damage is the following. If you _know_ it's a switch-mode PSU, and that
>the first thing it does is rectify the mains, and there's no
>line-frequency transformer to provide a startup voltage, then it'll run
>on DC, right. So give it DC at peak voltage of the 220V mains it's
>expecting - i.e. at twice the peak voltage of the local mains. Make an
>external voltage doubler to do this.
>
>I don't want to give more details, because IMHO if you can't work it
>out from that, then you probably shouldn't be doing it. Even if you do
>know what to do, examine the PSU carefully to make sure there's
_nothing_
>that depends on an AC input.
>
>-tony
>
>
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Received on Sat Sep 19 1998 - 14:48:59 BST