[sdiy] Newbie Voltage requirements question

[KA4HJH]

>I looked at the DS8 schematic, and
>it was immediately clear that 15v is out of the question as the 7805
>5v voltage regulators can handle 7.5v max according to the spec sheet
>I read.

You must have been looking at the *minimum* voltage spec for a 7805. The
max is something like 30 or 36V.

A close reading of the text reveals this: "The DS7 is powered by a 9V to
15V PSU single power supply or a 9V battery". My guess is that it draws so
little current that the regulator won't get very warm even at 15V so go for
it.

>So, this gets me thinking, why couldn't I replace the 7805's
>with 7815's? Obviously, the 16v caps would become 25v, but from what
>I saw in the spec sheets, the other components can all handle 15v.

Theoretically it would work but you might well have to monkey with the
values of some of the resisters to get it work properly again. It would be
easier to leave it the way it is.

>So, is it as easy as swapping out the Voltage regulators, or is there
>a lot more to it? I understand the principle of Ohm's law, V= I x R,
>but I am so new to electronics that I don't yet understand the
>ramifications on a circuit.

One thing that would happen is that the voltage divider made up of R26 and
R27 would put out 7.5V instead of 2.5V. That would probably screw up the
operation of the 3080 a bit.

There are people on this list that could go into this in much greater
detail than me. You're asking in the right place. But I'd build it the way
it is and be done with it.

-- 

Terry Bowman, KA4HJH
"The Mac Doctor"