DEC H7822 power supply

[Toby Thain]

On 2022-05-11 7:02 p.m., Peter Coghlan via cctalk wrote:
> It's hard to come up with suitable terms for this sort of stuff that
> convey the meaning of what is going on.  I struggled with it for a while
> and that was what I ended up with.
> 
> With the strict meaning of DC and AC being direct current and alternating
> current and given that we are often talking about voltages rather than
> currents, meanings are already getting stretched.  Besides, what's direct
> about it?  Maybe it would be more accurate to use terms like steady voltage

Many textbooks (and wikipedia) define DC as "in one direction", which is 
accurate. There is no need to refer to voltage; DC is indeed descriptive 
of the _current_ not voltage. "Constant voltage" is not a synonym for 
"DC", although it is a subset of DC we frequently encounter.

> and alternating voltage? Alternating doesn't seem like that good a term
> either.  To me it suggests some sort of square wave switching very rapidly
> between one extreme and another, not a nice lazy sine wave which is the
> normally accepted meaning.

Likewise, alternating means "alternating direction".

> 
> Given the normal usage that has evolved for the terms DC and AC rather than
> their dictionary definitions, I would suggest that the current that gets
> passed by a rectifier has both a DC component and an AC component.  When

It does not, due to unidirectionality.

> this mixture is fed into a transformer primary as in this case, the DC
> component does not pass through from the primary to the secondary but the
> AC component does.  Transformers only work on AC, right?
> 
> Or maybe it could equally be said that a transformer can be used to convert
> pulsed DC to AC?
> ...
> Regards,
> Peter Coghlan.
> 
> 
> Sent from my DEC Alphaserver 800
> 
> Wayne S wrote:
>>
>> “ The ripple on the rectified 5V and 12V supplies gets transformed into an
>> isolated AC source for the 9V supply.  ”
>> Shouldn’t that be “pulsed DC” instead of “AC” as rectification
>> changes AC to DC ?
>>
>>
>> Sent from my iPhone
>>
>>> On May 11, 2022, at 01:36, Peter Coghlan via cctalk <cctalk at classiccmp.org> wrote:
>>>
>>> The ripple on the rectified 5V and 12V supplies gets transformed into an
>>> isolated AC source for the 9V supply.
>>