[time-nuts] Re: Voltage Regulator

[Shawn]

On Mon, 2021-04-05 at 22:30 +0200, Attila Kinali wrote:
> On Sat, 03 Apr 2021 08:36:28 -0700
> Shawn <comsec at xmtservices.net> wrote:
> 
> > Tried putting an LM317 regulator in the line to drop the 30V supply
> > to
> > 10-12V and the power dissapation is beyond the heatsinking I have
> > that'll fit, also seems wasteful.  I have a switcher thatll fit the
> > bill but amd concerned about the noise inside the chassis that it
> > might
> > make.  I can bypass the input/output but concerned for radiated
> > hash
> > noise.
> 
> This depends. The MRT/FRK types are not that well shielded,
> but still better than modern telecom grade types. If you
> have a well designed switcher, then that should not be a
> problem. If you bought one of the many switcher on ebay/aliexpress,
> then I would not trust those... They are horribly designed,
> violating the layout rules in the datasheet (and those are
> already not up to time-nuts/noise-nuts standards). There are
> some 78xx replacments from reputable manufacturers (Murata, etc).
> Those should be good enough for that need. Still I would not place
> them close to the MRT, if possible.
> 
> 
> 			Attila Kinali
> 

Thanks Attila,

I have ordered a 24V low speed and a PWM 24V fan to try out.  Still
want to keep the loise down where I can so may still use a regulator
(the LM317 perhaps) to drop the 27V down to 20-23V and place the
regulator in the airway, prior to the FRK.  Hopefully there is a bit
more room so a larger heatsing will fit and allow the regulator to get
the necessary cooling.  The PWM fan idea Poul suggested is intriguing
and I may give that a try as well when the fans arrive.

I am assuming the PWM unit is quieter, electrically, than some units I
have found in the past, otherwise the linear approach will have to do,
assuming the thermal issues are addressed.

Shawn