From analogue-owner@hyperreal.com  Wed May 31 14:39:28 1995
From: apm@zeppelin.abl.ca (Andrew Paul Marriott)
Subject: +15/-15V power supply schematic
Date: Wed, 31 May 1995 17:28:58 -0400 (EDT)
Cc: analogue@hyperreal.com
Sender: analogue-owner@hyperreal.com
Precedence: bulk

As promised, here is a +15/-15V power supply, again from the Digisound
series.

Enjoy,

Paul.


Digisound 80 +15V/-15V DC stabilised power supply

Specification:

	output current 300mA per rail nominal, 450mA short circuit (protected)
	can be increased to 1A per rail

Components:

	R1	1k8
	R2	1R5 	2.5W wirewound note this is one point five ohms
	R3	3k3	metal film 100ppm TC or better
	R4	3k0	metal film 100ppm TC or better
	R5	1k2
	R6	1k8
	R7	1R5 	2.5W wirewound note this is one point five ohms
	R8	3k3	metal film 100ppm TC or better
	R9	3k0	metal film 100ppm TC or better
	R10	1k2
			all other resistors 5% or better metal or carbon film

        RV1	1k 	cermet trimmer
        RV2	1k 	cermet trimmer

	C1	2200uF  35V electrolytic
	C2	100nF   polyester
	C3	2u2	25V tantalum
	C4	1nF	polyester
	C5	10uF	25V tantalum
	C6	2200uF  35V electrolytic
	C7	100nF   polyester
	C8	2u2	25V tantalum	
	C9	1nF	polyester
	C10	10uF	25V tantalum	

	IC1	uA723C or equivalent
	IC2	uA723C or equivalent
	
	Q1	TIP31A or equivalent
	Q2	TIP31A or equivalent

	LED1	any red LED
	LED2	any red LED

	FS1	1 amp fuse
	FS2	1 amp fuse

	BR1	1.6A 200V bridge rectifier or equivalent
	BR2	1.6A 200V bridge rectifier or equivalent

	Xformer	secondaries 0:17V5, 0:17V5, 20VA


from "A"
   >----o---o------------------+---o-c   e ----+
        |   |                  |   | \   /^    |
        |   |                  |   |  ---  Q1  |
        |   |                  |   |   |b      |
        |   |                  |   |   |       |
        |   |               +------------+     |
        |   |               | 12  11   10|     |
        |   |               |            |     |
        |   |     +-----+---|6          2|-----o-----+-------+--------> +15V 
        |   |     |     |   |            |     |     |       |
        |   |     |    |-|  |            |    |-|    |      |-|
        |   |     |    | |R1|            |    | |R2  |      | |R5
        |   |     |    | |  |            |    | |    |      | |
        |   |     |    |-|  |            |    |-|    |      |-|
        |   |     |     |   |            |     |     |+      |
        |   |     |     +---|5          3|-----o    ===C5    |
        |   |     |         |            |     |    ---      |
        |   |     |         |            |     |     |       |
        |   |     |         |            |    |-|    |       |
        |   |     |         |            |    | |R3  |       |
        |   |     |         |            |    | |    |       |
        |   |     |         |            |    | |    |       |
        |   |     |         |            |    |-|    |       |
        |   |     |         |            |     |     |       |
        |+  |     |+        |    IC1     |     |     |       |
       ===  |    ===C3      |            |    |-|    |       |
       ---  |    ---        |            |    | |    |       |
        |C1 |     |         |           4|-o->| |RV1 |       |
        |   |     |         |            | |  | |    |      ---  
        |   |     |         |            | |  |-|    |      \ / 
        |  ---C2  |         | 7   13     | |   |     |       V LED1
        |  ---    |         +------------+ |   |     |      ---
        |   |     |           |   |        |   |     |       |
        |   |     |           |   |        |  |-|    |       |
        |   |     |           |   +-||-----+  | |R4  |       |
        |   |     |           |      C4       | |    |       |
        |   |     |           |               |-|    |       |
        |   |     |           |                |     |       |
   >----o---o-----o-----------o---o------------o-----o-------o----> OV 
from "B"                          |                  |       |
                                 ---                 |       |
                                  -                  |       |
from "C"                                             |       |
   >----o---o------------------+---o-c   e ----+     |       |
        |   |                  |   | \   /^    |     |       |
        |   |                  |   |  ---  Q2  |     |       |
        |   |                  |   |   |b      |     |       |
        |   |                  |   |   |       |     |       |
        |   |               +------------+     |     |       |
        |   |               | 12  11   10|     |     |       |
        |   |               |            |     |     |       |
        |   |     +-----+---|6          2|-----o-----+-------+
        |   |     |     |   |            |     |     |       |
        |   |     |    |-|  |            |    |-|    |      |-|
        |   |     |    | |R6|            |    | |R7  |      | |R10
        |   |     |    | |  |            |    | |    |      | |
        |   |     |    |-|  |            |    |-|    |      |-|
        |   |     |     |   |            |     |     |+      |
        |   |     |     +---|5          3|-----o    ===C10   |
        |   |     |         |            |     |    ---      |
        |   |     |         |            |    |-|    |       |
        |   |     |         |            |    | |R8  |       |
        |   |     |         |            |    | |    |       |
        |   |     |         |            |    | |    |       |
        |   |     |         |            |    |-|    |       |
        |   |     |         |            |     |     |       |
        |+  |     |+        |    IC2     |     |     |       |
       ===  |    ===C8      |            |    |-|    |       |
       ---  |    ---        |            |    | |    |       |
        |C6 |     |         |           4|-o->| |RV2 |       |
        |   |     |         |            | |  | |    |      ---  
        |   |     |         |            | |  |-|    |      \ / 
        |  ---C7  |         | 7   13     | |   |     |       V LED2
        |  ---    |         +------------+ |   |     |      ---
        |   |     |           |   |        |   |     |       |
        |   |     |           |   |        |  |-|    |       |
        |   |     |           |   +-||-----+  | |R9  |       |
        |   |     |           |      C9       | |    |       |
        |   |     |           |               |-|    |       |
        |   |     |           |                |     |       |
   >----o---o-----o-----------o----------------o-----o-------o--------> -15V
from "D"
                          17V5 AC
   >------   |||  ---===--+
  live     ) |||  )  FS1  |
          (  ||| (        |
           ) |||  )   +-------+
          (  ||| (    |   ~   |
           ) |||  )   |      +|------> To "A"
          (  ||| (    |       |
           ) |||  )   |  BR1  |
          (  ||| (    |      -|------> To "B"
           ) |||  )   |   ~   |
          (  ||| (    +-------+
           ) |||  )       |
          (  |||  --------+ 0 AC
 ground    ) |||           
 >---+    (  |||   --===--+ 17V5 AC      
     |     ) |||  )  FS2  |
     |    (  ||| (        |
    ---    ) |||  )   +-------+
     -    (  ||| (    |   ~   |
           ) |||  )   |      +|------> To "C"
          (  ||| (    |       |
           ) |||  )   |  BR2  |
          (  ||| (    |      -|------> To "D"
           ) |||  )   |   ~   |
          (  ||| (    +-------+
           ) |||  )       |
neutral   (  |||  --------+ 0 AC
    >----- ) |||

            Transformer T1

Primary should match your local supply voltage. A double pole switch should
be connected on the live and neutral supply lines.


Notes:

C1 and C2 should be physically close together, as should C6 and C7.

R2 (and R7) determine the short circuit current limits. To double the 
limit, halve these resistors. The power transistors Q1 and Q2 should be
mounted on heatsinks. If more than 1amp per rail is required, the transistors
should be replaced with higher power types and appropriate heatsinks used.

As with any circuit which is designed to be connected to the local domestic
power supply, care must be taken in construction to ensure safety. It
is highly recommended that the ground connection is made, even with 110V
domestic supplies.

Whilst I have taken every care in transcribing this schematic, I won't
be held responsible for people electrocuting themselves!

The LEDs are optional, if they are not required, resistors R5 and R10
can be removed.

Setting up:

Adjust RV1 to give +15V from the positive output rail and RV2 to give
-15V from the negative output rail. Allow to warm up and repeat the 
adjustments. Stable power supply rails are essential for proper operation
of voltage controlled synthesisers.

While this isn't the most modern power supply design in the world, it
is cheap and works well.