Transformer Questions
 

A friend of my has an old HP Jordana Organizer and the power transformer (the thing you plug into the wall, that is what it is called right?) is basically dead, it is 12v at 400ma, it also uses a special plug to get power into the Jordana unit. They asked me if i could fix it and I am planning to cut off the plug and solder it to a working 12v transformer, I am pretty sure that the amperage on the new unit does not matter as long as it is higher than 400ma is this is the case? I just don't want to fry the thing since it isn't mine.

Yep. 12V and greater than 400ma is all you need.

Thanks (why do messges need to be longer than 10 characters?)

Probably so people don't spam the boards with nonsense posts. (such as nothing but a smiley)

:evilaugh:

You also need to make sure that if the old transformer was DC, the new one is also DC, and vice versa. If you need a DC transformer and all you have is an AC version with the correct volt/amp parameters, it can be converted with a full bridge rectifier and maybe a few capacitors for filtering. This will drop the voltage ever so slightly however (maybe a fraction of a volt).

Also, you described an unregulated power supply. This means that different loads on something like that will get different voltages. You might want to make sure that you use something like a 7812 chip to regulate it, because mfgs use a specific transformer thats just right for the load, and you might not get lucky. Search for 7812 circuits.

On the other hand, it might work just fine. It depends on the power filtering circuits in the device being powered.