[sdiy] CEM3340: VCC +10V vs +11V

[Simon Brouwer]

Hi, 

I wonder about using a 7810 for that anyway, since its *nominal* output voltage
is 10V, so due to tolerance there is 50% chance the CEM3340 is operated below
even its original minimum spec. 
Also, looking at the Fairchild datasheet of the LM7810, it has a dropout voltage
of 2V typical, with no indication how that would decrease with lower current
than 1A. Powered from 12V (+/- how many %?), that gives little assurance that
the 7810 itself will work properly.

By the way, around 1980 I got some CEM3340 from Synton for, if I remember
correctly, around 40 NLG apiece, so the price hasn't changed too much in 35
years... and correcting for inflation, it is now about half as costly :)

Best regards
Simon

> On 06 June 2016 at 12:00 Florian Anwander <fanwander at mnet-online.de> wrote:
> 
> 
> You are right.
> 
> I got meanwhile also an answer from Dieter (english translation by me):
> 
> "We use 10V for the CEM3340, in order to achieve an even better 
> stability (if the + 12V would vary slightly, the internal 10V on the 
> module still are stable). But we had always problems, because obviously 
> not all CEM3340 worked properly with 10V(even if the datasheet indicated 
> so).
> In the last production series of the A-111-1, we bridged 7810and 
> operated the CEM3340 directly on 12V. The A-100PSU2 was so stable that 
> there were no problems here."
> 
> Florian
> 
> Am 06.06.2016 um 11:00 schrieb Vladimir Pantelic:
> >
> >
> > On Jun 6, 2016 10:38 AM, "Florian Anwander" <fanwander at mnet-online.de 
> > <mailto:fanwander at mnet-online.de>> wrote:
> > >
> > > What might be the reason to run the 3340 at a lower VCC?
> >
> > I see a 7810 regulator on the PCB, so I'd guess they wanted additional 
> > stabilization for the chip's supply voltage
> >
> 
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