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

Digital Voltmeter For Cars, February 2000:
(1) The 10μF capacitor adjacent to pin 2 of IC2 on the component overlay diagram (p28) should be 1μF, to agree with the circuit on page 25. (03/00)

(2) When using the voltmeter with 24V vehicles, the five 820Ω resistors will become quite hot. To alleviate this problem, we recommend replacing the 820Ω resistors with 10 1.8kΩ 1W resistors. Five can be installed on the PC board in place of the original 820Ω resistors. The other five can be installed underneath the PC board. Alternatively, use a 150Ω 10W wirewound resistor external to the voltmeter in place of the five 820Ω paralleled resistors which should be replaced with a short of a link. The 10W resistor must be placed on the metal chassis of the vehicle using a clamp and the connections insulated. The wiring should be clamped to the chassis to prevent breakage from the resistor leads. (08/00)

Ask Silicon Chip, March 2000:
The LM3886 bridge operation details were published in the June 1996 issue, not July 1996, as stated on page 105.

Ultra-LD 100W Amplifier, March & May 2000:
To eliminate a noticeable thump from the speakers at switch-off, we recommend that the 100μF capacitor connected to the regulated -55V rail be increased to 220μF 63VW.

RoomGuard Intruder Alarm, April 2000:
The 100kΩ resistor at the junction of D1, D2, D4 & pin 9 of IC1 on the circuit on page 31 should be 10kΩ. The wiring diagram on page 32 is correct.

Vintage Radio, April 2000:
In the circuit on page 61 the grid of the 6GW8 triode should be pin 1, not pin 3.

LED Dice, May 2000:
LED6 is shown back to front on the printed circuit board component overlay on page 60. Its cathode (the flat side) should go towards the top of the page. The circuit diagram on page 58 is correct.

PC-Controlled VHF FM Receiver, June 2000:
(1) The LM385Z isometric drawing on the circuit diagram shows the “ADJ” and “-” pins reversed.

(2) The circuit diagram on page 28 shows the incorrect pinouts on both the 2N7000 and LM336Z isometric drawings. Readingfrom the left, the 2N7000 should read “D G S” rather than “G D S” and the LM336Z has the “Adj” and “-” pins reversed.

Rain Gauge, June 2000:
the software for this project has a problem when used with the newer PIC16F84A version of the chip. The A suffix version has a faster EEPROM programming time and this interferes with the interrupt routine earlier than it does with the standard version of the PIC. It causes the daily rain readings to be randomly updated at 10 minute intervals into the next day rather than only once per day.

A new version of the software solves the problem. RAINA.ASM and RAINA.HEX software must be used with the PIC16F84A versions. This software will also run with the standard PIC16F84 and can be downloaded from our website: www.siliconchip.com.au

40V/1A Adjustable Power Supply, June & July 2000:
the LM336Z isometric drawing on the circuit diagram in the June issue shows the “ADJ” and “-” pins reversed.

Li'l PowerHouse, June & July 2000:
some constructors have not been able to calibrate the current reading successfully, finding that the current reading is too high and cannot be adjusted low enough with VR2. If you encounter this problem, try reducing the value of the 15kΩ resistor connected to pin 2 of IC2. We suggest a value of 7.5kΩ.

The final paragraph on page 60 of the June 2000 issue states that "IC2 is specified as an OP77GP which has the required low input offset voltage (typically 50mV).". This should read "(typically 50μV)".

The last paragraph of the first column on page 61 of the June 2000 issue states "In operation, VR2 sets the voltage on pin 4 of IC2 at between 0V and 1.25V". This should read "pin 6 of IC2".

The final paragraph on page 64 of the July 2000 issue states "Note that the wire connecting the pole of S4b to the PC board (and to the 100kΩ resistor at pin 2 of IC4)...". This should read "pin 3 of IC4".

Loudspeaker Protector & Fan Controller, August 2000:
the base resistor for Q8 on the wiring diagram on page 59 is incorrectly shown as 2kΩ . It should be 1.5kΩ , as shown on the circuit diagram on page 55. Also, the connections to LED1 and TH2 were incorrect. The connections should be as shown in the diagram on page 91 of the September 2000 issue.

Structured Cabling Systems, August 2000:
in the Cat5 cable diagram on page 74, pair 1 (blue/blue-white) are shown reversed - blue should connect to pin 4 and blue-white to pin 5 of the RJ45 jack. Fortunately, this diagram would rarely be translated into practice because the vast majority of RJ45 jacks are colour-coded to show which wires go to which pins.

Opto-Electronic Ignition, Circuit Notebook, October 2000:
the circuit featured on page 58 shows a 470Ω resistor connected to the collector of Q2 via a .01μF capacitor. This resistor should be 470kΩ .

2-Channel Guitar Preamplifier, November 2000:
the circuit diagram incorrectly shows S1 as a 2-pole (DPDT) power switch. It should be a SPDT type and it switches the Active mains lead only. In addition, the parts list for the main PC board contains some errors. First, there should be 6 x 2.2μF NP PC electrolytic capacitors (not 5) and 1 x 1μF NP PC electrolytic capacitor should be added to the list. Second, there should be 15 x 10kΩ resistors and 4 x 150Ω (not 14 & 3). Finally, the 4.7kΩ resistor connecting to pin 3 of IC3 on the overlay (Fig.4) should be 27kΩ .

2-Channel Guitar Preamp/Digital Reverb, December 2000:
pages 42 & 43 were inadvertently replaced by another article. The correct pages are published in the January 2001 issue.

Digital Reverberation Unit, December 2000 & January 2001:
the output resistor from pin 6 of IC3 is shown as 10kΩ on the PC board diagram on page 73 of the January 2001. It should be 150Ω , as shown on the circuit in the December 2000 issue. Also, the wiring diagram on page 68 of the January 2001 issue has the earth and signal connections reversed on the output of the digital reverb board.