[time-nuts] Voltage Regulator

[Shawn]

Hey Guys,

Have a couple questions.

First background:

Still refurbing some Efratom MRT Rb units, mostly filter caps and a
bridge rectifier or two, plus SLA batteries.

One of the units is a rack mount high temperature model, the FRK unit
is external to the power supply chassis and has a fan on it.  The fan
is a 12V unit, though it has been changed before so could've been a
24V, the supply runs around 27V and was at 30V no load and there was a
carbonized probably 20 ohm 1W resistor in the supply line for the fan.
The fan is in good shape and I'dlike to keep it, low speed and quiet.

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.

Question 1: Do I really need to be concerned about the noise inside the
chassis?

Question 2: Should I just replace the fan with a 24V unit and put a 10-
20 ohm resistor inline to lower the speed? (probably the better choice
but I'd love to hear your suggestions.)

Shawn