On 07/02/2015 12:08, Dave Plowman (News) wrote:
Is definitely my week for computer related problems. Latest one is the KVM
switch.

It's an Aten DVI/PS2 unit which cost quite a bit and looks well made -
it's in a steel case.

Symptoms are it no longer works with only one computer switched on. Boot
the second one and things do eventually all work. But the impression is it
will eventually fail.

So on the principle it is usually a power supply fault I removed it and
measured its incoming voltage under load on the bench - it uses a wall
wart to provide the DC.

Measured at just over 4v.

Wall wart says 5.3v and 2.4 amps, and by the weight/size is an SMPS.

Using my bench top 5v 3 amp supply it works normally.

A new wall wart from Aten is 35 quid plus. ;-)

How about a tenner from Rapid? Or probably cheaper still on eBay -
though you might have to change the connector to match polarity and
diameter of the KVM socket. My latest KVM is USB powered by the PCs that
it serves and as such requires no extra mains.

http://www.rapidonline.com/Electrica...V-2-5A-85-2940

One feeble old PC isn't very keen on driving it on its own.

Anyone know where I can buy a suitable one at a sensible price? It doesn't
have to be a wall wart.

Or I suppose I could just make a linear one?

Not worth the effort a linear one tends to run a bit too warm for
continuous use and life is too short to DIY wall warts. Mending them is
possible if you can get into them and safely reseal again afterwards.

Dessicated high ripple smoothing capacitor would be my guess.

--
Regards,
Martin Brown