Here is a circuit from Chrissi ZR6CPB.
ZR6CPB PRECISION ADJUSTABLE LAB POWER SUPPLY Mark II Low 3-15V 0-30A
Hi 15-33V 0-15A
+-----------------+----+----+----+----+----+
| | | | | | | /
(Low Voltage) |TIP3055 or 2N3055| x6 | | | | | /
(Hi Current) | | /c | / | / | / | / | / /
| | b |/ |/ |/ |/ |/ |/ /
| +-----+----+----+----+----+----+ /
Low Off Hi-(Hi Voltage)| | |\ |\ |\ |\ |\ |\ /
+-------+ (Low Current)| | | Ve | V | V | V | V | V
| | | ------- | | | | | | | h
-+-o o o-+ | | | | | | | | | | e
Mains ^ | > O < | \ \ \ \ \ \ a
Live | | | | | / / / / / / t
O DP3T(Centre Off)| ------- | 0R2\ 0R2\ 0R2\ 0R2\ 0R2\ 0R2\ s
| Switch | | | | 5W / 5W / 5W/ 5W / 5W / 5W / i
<-----+ | |L200 | | \ \ \ \ \ \ n Transformer Live | | | | | | | | | | k
| ------- |current| | | | | |
| 1|||||5 | 1 K | | | | | |
| ||||| | /\/\/\+----+----+----+----+----+-> Transformer 12-0-12 15A | ||||| | ^ | | | + +---------+-+ +---+-----+--+|+|+-++ | | | |
\ | | | | | ||| | | | | | 3-33 V
/ | | | | | ||+ | | / | |
\ 12V RMS - v | | | +|--------+ \ | | 0-30 A
/ ^ _ | |40V |50v || | / | |
\ Off | | | +|4700u|0.1u|| | voltage\10K | +| 4700uf
/ Low Hi | | | ----- ----- |+---------->/ ---- -----
+--o o o--+ +--+ /---\ ----- | | | ---- /---\ 40V
/ct ^ | | | | |0.1|uf | | 0.1|uf |
\ | | | +<36V| | | ----- \ |50V |
/ O v - | | | ----- /1K | |
\12V | _ ^ | | | |50V \ | |
/RMS | | | | | | | / | |
\ | | | - | | | | | | | - +---------+-+ +--+-----+----+---+--------+----+----+---------------->
| |
+----------+
--- (ground)
-
.
DP3T switch with centre off - selects between LO, OFF & Hi.
Enjoy! From
ZR6CPB@ZS0TFK.LIC.NWP.ZAF.AF
Also see my tech bul "0-35V 0-5A Lab PSU CS FL-305".
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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ARGEN-X BBS - IPV6 TELNET LU9DCE.DYNU.COM -----------------------------------------
--- Mystic BBS v1.12 A48 (Linux/64)
* Origin: ARGEN-X BBS (4:902/6)