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Notes & Errata Advertising Index Altronics.................................. 78-81 LK3 Clarke & Severn Electronics.......... 7 330Ω A LED2 BLUE λ K +12V 82Ω 1W K D6 1N4007 100 µF 16V RLY2 A HEADPHONES C SPEAKER/HEADPHONE SWITCHING K RLY1 470Ω Q9 BC547 TO "IN" (PIN 3) OF REG1 A D9 1N4004 Emona Instruments........................ 5 Hammond Manufacturing............... 7 Hare & Forbes............................. 2-3 High Profile Communications..... 103 Icom Australia.............................. 91 B Jaycar .............................. IFC,49-56 E NC 4007 D6 RLY1 COIL 100µF NO Keith Rippon .............................. 103 Keysight Technology................. OBC KitStop............................................ 8 LD Electronics............................ 103 COMMON Q9 470Ω BC547 REG1 LM/LT1084–ADJ LEDsales.................................... 103 Master Instruments.................... 103 Microchip Technology................... 11 Insulating washer & bush Mikroelektronika......................... IBC Ocean Controls............................ 12 Qualieco....................................... 59 Questronix.................................. 103 560Ω 100 µF 4004 470Ω 120Ω Currawong 2 x 10W Stereo Valve Amplifier (November 2014 - January 2015): the relays intended to switch the signal over from speakers to headphones do not operate correctly. Three components must be changed or added to fix this and these changes can be made without removing the PCB from the case. The accompanying two diagrams show the modifications to the circuit and PCB in red. The 10kΩ resistor can simply be shunted with a 470Ω resistor. The added capacitor is shown on its side for clarity however it should go above D6. Make sure the leads of the added diode can’t short to the leads of the 560Ω resistor or pin 2 of REG1. With these changes, the relay holding voltage is around 3.6V which is sufficient. Finally, in the parts list on page 35 of the November 2014 issue, the 470 Ω 1W KCS Trade Pty Ltd........................ 29 Radio, TV & Hobbies DVD............ 20 + 100 µF 50V 82 Ω 1W LK1 LK3 Sesame Electronics................... 103 Silicon Chip Binders................... 101 Silicon Chip Online Shop........ 35,97 8 x 220μF 630V polyester capacitors should be 8 x 220nF 630V instead. Silicon Chip PCBs...................... 103 Silvertone Electronics.................... 9 Tronixlabs................................... 103 Ask SILICON CHIP . . . continued from page 102 than the digital display included in the project? Perhaps something off eBay? A bargraph or rotating dial pointer is quicker to read at a glance, especially if the value is constantly changing – it’s the old analog clock-face or speedo versus a digital fast changing numbers readout thing. (S. S., via email). • The signal presented to the ECU is a narrow-band oxygen sensor simulation that is derived from the wideband sensor readings. So the ECU is not fed anything different to what it is designed to receive – a standard narrow-band signal that has a sharp change in voltage at stoichiometric mixtures. We don’t alter the narrow-band response from that obtained via the wideband sensor. We did try 104  Silicon Chip incorporating a small amount of averaging of the signal during project development but that slowed down the overall sensor response signal applied to the ECU. Also, we do not alter the oscillating voltage narrow-band signal as the ECU is expecting a signal that will switch sharply in voltage about the stoichiometric point. Any smoothing or voltage range restriction can cause the ECU to present an error code due to the sensor not producing the expected signal. Note that the voltage range from the simulated narrow-band sensor output at the sharp transition about stoichiometric still represents a very small mixture change even though the voltage range varies by several hundred millivolts from 0.45V. The wide-band sensor allows for an accurate mixture reading to be observed. You can use an analog meter Wiltronics...................................... 13 Worldwide Elect. Components... 103 if it can be arranged to operate over a 0-5V range. 0V represents a lambda of 0.7 and 5V a lambda of 1.84. Query about phase splitter circuit I have noticed an error in the main circuit diagram of the Currawong valve amplifier in the November 2014 issue. The phase splitter has unequal resistors (120Ω and 220kΩ) in the anodes. From the text, I guess that both should be 220kΩ. (J. G., via email). • It may look incorrect but it’s not. After a lot of experimentation, we found that this configuration gave the best symmetrical drive to the output SC valves. siliconchip.com.au