[time-nuts] power supplies

[jimlux]

On 5/1/20 12:07 PM, Tim Shoppa wrote:
> Jim, when it comes to "bench supplies" - knobs for voltage and meters -
> most of the commonly available Chinese bench supplies in the under 3A-range
> are linear with series regulator.
> 
> This unit (HY1803D) is typical and has a transformer (relay-selected
> winding depending on the voltage setting) and a 2N3055 heat sink on the
> back.
> http://www.mastechpowersupplies.com/variable-regulated-power-supply-hy1803d.html
> 
> After you get to the 5A range they start becoming switchers. There are only
> a couple of common designs with different trim and brand names on the front.
> 
> Of course old-school (50's-80's era) regulated HP bench supplies are
> commonly available on the surplus market and they are built like tanks and
> pretty much infinitely repairable as long as the meters haven't been
> smashed in.



True, but these days, I'd rather fool with oscillators and mixers than 
power supply repair.  I've kind of gotten out of the "buy old surplus 
gear and make do" phase. Although if you go somewhere like the San 
Bernardino Microwave Society meetings, there's people there with literal 
truck loads of old test gear, for which I would have sold my future 
children into bondage for, when it was only 20 years old - of course, 
now it's 50 years old.

I'm past the thrill of running a 1980s sweeper or the venerable 8640 
signal generator.

Hence the question about "off the shelf bench power supplies"





> 
> I would be reluctant to use a bench supply for long-term use because you
> bump that knob and what was supposed to be 3.3V becomes 18V.


Uh, no, I'd never do that, no, uh-uh.  At JPL we have bunches of 
overvoltage protector widgets from some company I can't remember, banana 
plugs or wires, external to the bench supply.  If you go over 5.25V, it 
crowbars.


> 
> Few to no current production wall warts are linear. Power-conserving
> regulations around the world now pretty much require wall warts to be
> switchers. Linear (including regulated) wall warts are still available from
> the surplus outlets but they are less common than before.

yeah, i've got a box of those older linear warts - a transformer, a 
diode, maybe a bridge, and maybe a capacitor.   Good for stuff like 
running LEDs or small motors.


> 
> Few to no current production modular fixed-voltage supplies are linear.
> With a handful of exceptions (I think a couple of the Lambda linear modules
> are still available) they are almost all switchers.

Acopian is your friend for linear "bricks".

https://www.acopian.com/linear-regulated-power-supply-models.html

That familiar gold box is a common sight.