So I've taken apart a Sharp GF9191 which is a 12v box.  When I've checked the voltage of the power supply its a constant 15.8v.  So the question is whether I could use this power supply in my Sharp GF9000 (a 15v box) that has no power supply or is it normal for the supply to run a chunk higher so by the time its worked its way through the system it runs at the required 12v?

Hi Si

The "off load" voltage can be two or 3 volts higher than when loaded. The GF9191 power supply will not have the beens to drive the 9000. I would expect the 9000 power supply to read 17 or 18 volts off load.

I thought that might be the answer...oh well.

On the plus side I do have a GF575 I might scrap for the power supply and this is a 15v box...the only issue is that I can't follow the circuitry...the 9000 has just the + and - wires but the 575 has all sorts of wires milling around the power supply

You would have to show me the circuit mate; but by the time the 9000 came along I think they would have rationalised the desighn quite a lot. Don't scrap the power supply though, worth keeping as a spare.

Batteries will sometimes measure a few millivolts sometimes half a volt more off load than on load, however there current delivery is good so the volt drop on load should not be that great. (Untill they get old) An off the shelf 15v power supply will have a voltage regulator in it (I think Si was measuring 15v from his 9191 at a point before the voltage regulator, which is on the main board) Having a voltage regulator circuit ensures that on load or off load you get 15v. (As long as you are not drawing more current than it is desighned to supply) So if you are running the machine from batteries (as long as they are good hi power ones) or from a 15v regulated power supply (with a sufficient current rating) your machine should be performing at full potential

Interesting info and yes I was reading it direct off the supply before the board.  Oh and don't worry nothing gets scrapped here...anything that could be used again gets boxed up in the shed until its needed

I've got the service manual for the 575 and 9000, would this help as I'd love to whip the supply out of the 575 and bung it in the 9000...my 9000 has none of the power supply and anything attached, just a big empty space in the corner!

Hi Si

I will look into this later (still at work).  Just to clear things in my mind, is the 9000,s power supply missing or faulty. I havn't looked at the manual yet but I suspect that the voltage regulator circuits on the 9000 are part of the power supply module rather than being on the main board (as in earlier Sharps). If this is the case it may be possible to build a replacement module (Although you would have to be carefull with the mains inlet.) If you still have the 9000's power supply it may not be dificult to repair. Anyway, I shall give you a more considerd opinion later. Cheers, Seb