siliconchip.com.au Australia’s electronics magazine April 2019 41
SHOP (SC0782) or, if you purchase the kit from Jaycar, the
PCB will be included.
See below for the list of parts you’ll need to build it.
Start assembly by fitting the the two resistors and then
the six diodes (with the polarity shown in Fig.13).
Next, mount the LEDs with the longer (anode) leads to-
wards the bottom of the board. Follow with the two MKT
capacitors.
You can then fit the two 3-way terminal blocks, with
the wire entry holes facing the nearest edge of the board.
Now solder REG1 & REG2 with the tabs towards the
board edge as shown, taking care not to get the two mixed
up. Finally, solder the four capacitors in place, ensuring
that their longer (positive) leads go into the pads marked
with a “+” symbol.
The photo above shows two flag heatsinks (and they are
mentioned in the parts list). It won’t hurt to fit these, but if
you’re only going to be powering the preamplifier and your
transformer secondary voltage is the recommended value,
they should not be necessary since the preamp doesn’t
draw a lot of current.
Building the full power supply
The circuit of the Ultra-LD power supply is shown in
Fig.14. The bottom section is similar to the Universal Reg-
ulator supply described above and operates in the same
manner. A chassis-mount bridge rectifier is used for the
high-voltage AC secondaries of the power transformer,
which are shown as 40-0-40V here, but lower voltages can
be used with this board too.
The resulting DC rails are then filtered by three 4700μF
capacitors each and made available at CON1 and CON2,
to be fed to the amplifier modules.
Fig.15 is the PCB overlay for this supply. You can pur-
chase this PCB from the SILICON CHIP ONLINE SHOP (SC0716)
The two wire links should not be necessary as our boards
are double-sided and have copper strips on the top lay-
er connecting these points, but if you etch a single-sided
board, you will need to fit the two links using 1mm diam-
eter tinned or enamelled copper wire.
Next, mount the diodes with the orientation shown, then
the LEDs, with the longer (anode) leads towards the top of
the board. You can then bend the regulator leads to fit the
hole pattern on the PCB and attach their tabs to the board
securely using M3 machine screws and nuts.
Once you’ve checked that they are straight, solder and
trim the leads.
The terminal blocks go in next. Dovetail CON4 with
SC
2011 ©
Regulatoriversal Un+^18103111+GInSC
100nF100nFACINPUTDCOUTPUTD1D4D2
D3LED11.5kW1.5kWREG1REG2
LED2C1 2200 μFC2 2200 μF100 μF100 μF –+18103111
© 2011++++ CON2400440044004
40044004
4004D5D6CON111(^22)
3
3
0V
Fig.13: this PCB overlay corresponds with the circuit of
Fig.12. You could fit flag heatsinks to REG1 & REG2 but
they are not strictly necessary for use with the preamp, as it
doesn’t draw a lot of current.
Parts list for
Universal Regulator (±15V outputs)
1 PCB, code 18103111, 71 x 35.5mm
1 transformer, 230V AC primary, 15-0-15V AC or 230V AC to
15V AC plugpack to suit (see text)
2 3-way terminal blocks, 5.08mm pitch
4 tapped spacers
4 M3 x 6mm machine screws
2 TO-220 heatsinks (optional)
2 M3 x 10mm machine screws, nuts and shakeproof
washers for heatsinks (optional)
Semiconductors
1 7815 +15V linear regulator
1 7915 -15V linear regulator
6 1N4004 diodes
1 red 5mm LED
1 green 5mm LED
Capacitors
2 2200μF 25V electrolytics
2 100μF 25V electrolytics
2 100nF MKT
Resistors (all 0.25W 1% metal film)
2 1.5kW
Parts list for
Ultra-LD Amplifier and preamplifier
power supply (±57V and ±15V outputs)
1 PCB, code 01109111, 141 x 80mm
1 transformer, 40-0-40V and 15-0-15V AC secondaries (see
text)
4 3-way PCB-mount terminal blocks, 5.08mm pitch
(Altronics P2035A or equivalent) (CON1-4)
2 2-way PCB-mount terminal blocks, 5.08mm pitch
(Altronics P2034A) (CON5-6)
3 PCB-mount or chassis-mount spade connectors [Altronics
H2094]
3 M4 x 10mm screws, nuts, flat washers and shakeproof
washers (if using chassis-mount spade connectors)
4 M3 x 9mm tapped Nylon spacers
6 M3 x 6mm machine screws
2 M3 shakeproof washers and nuts
150mm 0.7mm diameter tinned copper wire
Semiconductors
1 35A 400W chassis-mounting bridge rectifier (BR1)
1 7815 1A 15V positive linear regulator (REG1)
1 7915 1A 15V negative linear regulator (REG2)
4 1N4004 1A diodes (D1-D4)
1 5mm green LED (LED1)
1 5mm red LED (LED2)
Capacitors
6 4700μF 63V electrolytic
2 2200μF 25V electrolytic
2 220μF 16V electrolytic
Resistors
2 3.3kW 5W