"Sparta" writes:

Anyone built the power supply from "electricity & electronics" by randy
slone?

I just completed construction of this power supply and made the
modifications on page 333 using the IC voltage regulators (nte956 and
nte957). My input voltage is about 36v however the output voltage from
the IC is about 28v.

The previous circuit that did not use the IC's gave a variable output
of about +- 3.8 to 36 volts DC. Now I'm getting about +- 1.2 to 28.
I'm wondering that if incorporating the IC's to improve the voltage
regulation under load is the cause of this? Is this the expected
outcome?

Here is a diagram of the positive side of the regulated power supply.


36V
raw
+dc__________________NTE956_______________________ ___________Regulated
V Pos.
| | | |
| | | |
+ |_____220 ohm 2W 10uF 35VDC
4700uF 50W | |
- 5Kohm 2W potentiometer 10uF 35VDC
| | |
| | |
Circuit Common Circuit Common Circuit Common

You can figure it out yourself. The voltage regulator's mission in life
is to make sure there is about 1.25 V across the 220 ohm resistor.
In order for that to be the case (assuming there is negligible
current from the IC common terminal), then you have a voltage divider
formed by the 220 ohm resistor and 5K pot. Comes out to a bit over 28 V.

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