In article <5247c9cd51.Andrew-Pin@xxxxxxxxxxxx>, Andrew Pinder <Andrew.Pinder@xxxxxxxxxxxxx> wrote: > In message <f830bdcd51.davehigton@xxxxxxxxxxxxx> > on 3 May 2011 Dave Higton <davehigton@xxxxxxxxxxxxx> wrote: > > In message <51cbb06213julie@xxxxxxxxxxxxxxxxxxxxxxx> > > Julie <julie@xxxxxxxxxxxxxxxxxxxxxxx> wrote: > >> I have never been able to understand why the voltage is this critical. > >> Neither does my OH. We are both electronics engineers. Back in the > >> good old days, TTL would tolerate 4.75 - 5.25V, 7V absolute max. > >> CMOS could run anywhere between 3V and 18V. (I know that many of the > >> more recent ICs run at 3.3V.) Why is the Iyonix so sensitive? > > JB has given the real answer: the Iyonix isn't particularly > > sensitive, but its PSU ages and malfunctions. > I realise that designing and producing the Iyonix was a major > achievement by a small firm and that there must have been complex > trade-offs but: > 1 Acorn hardware tended to last a long time. So it was likely that > buyers would expect the Iyonix to carry on performing even with its > PSU ageing. Of course, if Castle had been able to produce completely > new models every 12 months this wouldn't have been an issue. > 2 Given that PSUs ageing will happen in largely predictable ways, i don't think they do. My Iyonix, one of the very early ones had a power suppply failure at about 15 months. The replacement one (from Castle) has worked perfectly since then. > a design that could cope with the ripple on the 5V line going out of > spec would be more robust and hence more durable than one that can't. since Castle were reliant on off-the shelf components, this is rather an impossible request. -- From KT24 Using a RISC OS computer running v5.16 --- To alter your preferences or leave the group, visit //www.freelists.org/list/iyonix-support Other info via //www.freelists.org/webpage/iyonix-support List-related queries to iyonix-support-moderators@xxxxxxxxxxxxx