Random DEC Questions

tony duell ard at p850ug1.demon.co.uk
Mon Dec 1 00:16:11 CST 2014

> Not sure what makes it an international model, although it does say 50-60Hz,
> and it does not have a captive power cord, so presumably it is an
> international one. I will have to take a look inside, but I really don't
> have any idea what I would need to do to convert it.

Nothing specific to the VT3xx

Normally SMPSUs that can be converted to run off 115V or 230V 
mains run the chopper off about 350V DC. The mains input
rectifier circuit is configured to be a simple bridge rectifier
for 230V and a voltage doubler for 115V. The conversion is
nothing more than a link from the neutral side of the mains
to the centre tap of a pair of smoothing capacitors in series
(if you look at the circuit, you end up with 2 diodes that are
redundant, always reverse-biased, in the voltage doubler
circuit, but that is no problem).

So look for a link on the PSU board in this area. If you are
lucky it will either have 2 positions labelled '115V' and
'230V' (in the latter position it actually does nothing) or
will be marked 'fit for 115V' or something.


More information about the cctech mailing list