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

Woofer Stopper MkII, February 1996:
depending on which type of piezo loudspeakers are used, they can produce audible clicking at the rate the signal bursts to a high and low level. This can be cured by adding a 47μF 16VW electrolytic capacitor between the base and emitter of transistor Q3. The positive side of the capacitor connects to the base. The capacitor effectively slows down the rate that the burst signal rises and falls to eliminate any audible noise in the speaker. We should also point out that if the tweeter drive level control (VR2) is set too high, it can cause the same symptom.

Kill Switch For Smoke Detectors, February 1996:
if you have trouble sourcing the BS170 Mosfet specified for this project, try Farnell Electronic Components, in Sydney (telephone 02 9645 8888 or visit www.farnell.com); or you can substitute a VN10KM, which is available from Dick Smith Electronics stores.

Radio Control 8-Channel Encoder, March 1996:
in the circuit on pages 56 & 57, R19, the 10kΩ resistor at pin 6 of IC3b, should connect to pin 5 instead. It comprises a voltage divider with R13, a 22kΩ resistor.

175W Power Amplifier, April 1996:
to further increase the safety margin in the event of amplifier failure, we suggest that the fuses be changed to 3A instead of 5A when 8Ω loudspeakers are used.

Insulation Tester, May 1996: the overlay and wiring diagram on page 34 is incorrect. It shows the battery connections reversed. Also the 47kΩ resistor adjacent to the 36kΩ and 120kΩ resistors should be 43kΩ.

Stereo Simulator, June 1996:
pin 7 of the M65830P (IC2) is shown connected to both +5V & GND on the circuit diagram on page 16; it should only be connected to +5V. The PCB overlay diagram on page 19 is correct.

Remote Control Extender, July 1996:
this project was previously found to be incompatible with Mitsubishi VCRs. However a reader has discovered that it can be made to work if the Mitsubishi VCR's remote is used to program an AR-1712 (4-in-1 model) learning remote (available from Jaycar). (09/02)

16V 15A Power Supply, Circuit Notebook, July 1996:
there are a number of mistakes in the circuit on page 17. First, the 56kΩ resistor from the collector of Q4 should go to the +25V line instead of to the base of Q1. Second, D4 should be a LED. It has also been suggested that the 100μF capacitor across the output terminals be increased to 220μF & a 1kΩ resistor be connected across the 10kΩ potentiometer VR3 (Voltage Max).

2-Amp SLA Battery Charger, July 1996:
the wiring diagram on page 57 has reversed polarity signs on the output cable crocodile clips. The cable coming from the left hand side of the printed circuit board should be positive.

Fluorescent Lamp Starter, August 1996:
the circuit diagram on page 16 shows D1-D4 as 1N4004 diodes. They should be 1N4007 1000V types, as specified in the parts list.

Video Transmitter/Receiver, October 1996:
it has been pointed out that some video camera modules have a DC output instead of AC. If these are used with the Video Transmitter it will not work. The cure is to connect a 100μF non-polarised electrolytic capacitor in series with the input socket. This can be wired directly between the RCA input socket and the input on the PC board.

Multimedia Amplifier, October 1996:
there is an error with the test procedure for the PC board. Without the power link installed, pins 1 and 9 of IC3, IC4 and IC5 are at about +0.5V and pin 7 is at +12V. No voltage is present on the other pins. With the link in, pins 1 and 9 are at about +2.2V; pins 3, 4 & 6 are at +5.6V; and pin 7 measures +12V.

MultiMedia Loudspeakers, November 1996:
the perspective diagram on page 61 shows the wrong enclosure depth; it should be 224mm.

LPATS, November 1996:
the text on page 8, and in Fig.1 on page 6, refers to "parabolas" as the paths of possible lightning strikes. The term used should have been "hyperbola".