PC Boards for most Silicon Chip (plus EA & ETI) projects can be obtained from RCS Radio, Sydney.
Phone (02) 9738 0330. Fax (02) 9738 0334. Email sales@rcsradio.com.au or visit www.rcsradio.com.au

50-Watt Stereo Amplifier Module, February 1995:
The parts list should show 2 x 22μF 16VW electrolytic capacitors (not 4). In addition, there should be 2 x 47μF 16VW electrolytic capacitors.

Digital Effects Unit, February 1995:
The parts list should show 19 330Ω resistors rather than one. On the circuit (Fig.2), the 3.3kΩ resistor shown at the input to the modulation filter should be 22kΩ . An extra 3.3kΩ resistor should be included between the positive side of the 100μF capacitor and the junction of the 1.8kΩ and 22kΩ resistors.

Finally, the two 56pF capacitors shown on the PC board overlay (Fig.3) should each be 560pF, while the unmarked electrolytic capacitor at top right should be labelled 10μF.

Photographic Timer, April 1995:
The bridge rectifier specified as "WO4" does not have the same pinout as the DIP rectifier depicted on the PC overlay on page 27. If a WO4 type is used, two of the leads will have to be swapped and sleeved so it can be installed in the PC board.

Mains Music Transmitter & Receiver, May 1995:
A number of errors have appeared on the circuit and wiring diagrams for the receiver.

C4 is shown as 330pF on the circuit & .0033μF on the wiring diagram; 330pF is correct. C17 is shown as .0047μF on the circuit & .015μF on the wiring diagram; .015μF is correct. C25 is shown as .0047μF on the circuit but not marked on the wiring diagram; the correct value is .0033μF. C28 is shown incorrectly polarised on the wiring diagram but the circuit is correct.

The cathode of diode D2 is shown connected to the junction of C11 and R9 on the circuit but incorrectly shown on the wiring diagram as connected to the wiper of trimpot VR2. To correct this, the track section connecting D2 to the wiper of VR2 should be cut and then linked to the junction of C11 and R9. The circuit board will work as presented but will not mute fully when no carrier signal is present.

Walkaround Throttle, Ask Silicon Chip, May 1995:
The suggested wiring diagram, on page 93, for a centre-tap transformer shows the 10μF capacitor near the 7812 reverse biased. The capacitor’s negative connection should go to the centre pin of the 7812.

Electric Fence Controller, July 1995:
It has been brought to our attention that Australian Standard 3129-1981 for Electric Fence Controllers has been superseded by the new standard AS/NZS 3129.1:1993. This specifies a maximum fence output of 10kV compared to the previous limit of 5kV. In order to increase the output of our Fence Controller to 10kV, change the 6.8Ω 1W resistor in series with the ignition coil to 1.2Ω 0.5W. No other changes are necessary.

(2) Some readers have complained about insufficient HT output from this circuit. We have been advised by Dick Smith Electronics that the resistance of the 250mA fuse can be critical in this respect. Typical 250mA fast-blo fuses have a resistance of 11W & this will have an effect on the HT output. To avoid this problem, we suggest using a 500mA fuse; typically these have a resistance of less than 1Ω.

Fuel Injector Monitor, August 1995:
(1) The specified LM358 op amp has been found to be non-linear in the circuit at low & high injector duty cycles. The problem is corrected by substituting an RCA CA 3260E op amp which has CMOS outputs. This op amp is a drop-in replacement but a change to the integration RC network at pin 3 is desirable. Change the 4.7kΩ resistor to 47kΩ & the 220μF capacitor to 10μF. (2) We have recently seen a fuel injector monitor in which only eight of the LEDs would light instead of the full 16. The problem is that differing switching thresholds on the 4053 (IC2) can cause faulty switching of the LM3914 dot/bar modes. If this occurs, the cure is to replace zener diode ZD1 with a 1μF electrolytic capacitor, with its negative lead connected to pin 3 of IC5.

Railpower MkII, September & October 1995:
The component overlay diagram on page 33 shows a .0047μF MKT capacitor connected to pin 10 of IC1. The value should be .047μF.

Extra Fast Nicad Charger, October 1995:
The lengths of the 0.8mm wires specified for the primary & secondary windings of transformer T1 are incorrect, although the number of turns and the turns ratio are correct.

The length of the quadrifilar primary wires should be 1.7m before termination, while the two secondary wires (bifilar) should be 3.5m.

Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1, November 1995:
The anode of diode D12 is shown incorrectly joined to the junction of the cathode of D14 and an associated 10kΩ resistor. Instead, D14 and the 10kΩ resistor should connect directly to the push-button switch S7.

Dolby Pro Logic Surround Sound Decoder Mk.2, November & December 1995:
The +5V & GND connections for the microprocessor board (01409954) are shown transposed on the overlay diagram in the December issue. The wiring diagram on page 74 of the same issue needs to be altered so that wire "26" goes to the left pin while the wire from the power supply board goes to the right pin. Wires shown connecting to switch S4 are correct. The reference to IC4 in the seventh line, third column on page 78 should be to IC6.

Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2, December 1995:
The resistor connected to pin 21 of IC2 is marked "30O" on the layout diagram (Fig.4, page 71). The correct value of this resistor is 30Ω.

Five-Band Equaliser, December 1995:
The supply pins for IC2 on the circuit diagram (Fig.5, p24) are shown reversed. Pin 4 should go to the +15V rail, while pin 11 should go to -15V. The parts layout diagram (Fig.6, p25) is correct.

Subwoofer Controller, December 1995:
The circuit diagram on page 40 should show R34 directly connected to +12V to agree with the PC board overlay diagram on page 41; R34 does not connect to R7, C5 and pin 8 of IC2a as shown on the circuit. While the board will work, it ideally should be altered to agree with the circuit. D1 and D2 on the same board diagram are shown transposed although this has no effect on circuit operation.

Engine Immobiliser, December 1995:
We have had reports of the zener diodes in this circuit failing. In line with our circuit practice for high energy ignition systems, the specified zener diodes should be rated at 5W instead of 1W.