[Gllug] [OT] 30V PSU required for HP scanner

[Chris Bell]

On Sat 25 May, Emil Vaughan wrote:
> 
> Hi all,
> 
> I've been trying to find somewhere where I can find a cheap 30V AC/DC adaptor
> for an HP Scanjet 4100C. It seems that the only 30VDC supplies are to be found
> in expensive lap equipment. So I was wondering whether replacing the rectifier
> circuit in 13.8V supply with a voltage doubler circuit would work? Or does
> anyone know how I can get a 30V power supply?
> 
   Whichever way you do it, it must be able to supply the correct voltage
and current within the required specifications. A voltage doubler circuit
will not give exactly double because of losses, and it introduces extra
ripple which must be filtered. Correctly designed switch mode power supplies
produce little waste heat, but a simple transformer, (bridge) rectifier,
capacitor smoothing, and series regulator can be cheaper for low power
requirements. If you have a faulty HP PSU, disconnect it from the mains and
see what they have bodged inside.
   If you need spares, try BV Computer Maintenance, 020 8571 3377,
(Southall, Hayes area, a friend of mine who has supplied and repaired
computer hardware for many years).

-- 
Chris Bell



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