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Connecting the high energy ignition system I’ve just finished constructing the Universal High Energy Ignition (June 1998) to put into my 1979 Toyota Corolla but I am having a little difficulty with the connections. I have tested the unit and adjusted the current limit adjustment as described in the text. The transistor is correctly mounted and is not shorting out on the case. In the text, it describes connecting the wires as follows: one to the coil negative, +12V from the ignition, earth to the case and then to the chassis, tacho to the tacho (I already have the electronic tacho fitted) and points to the points. The coil is a standard type with an external ballast resis­ tor, connected to a single points-type distributor incorporating a condenser and noise resistor. This is where I am having troubles. All is connected as above, but the car won’t start. Now do I have to remove the existing wire that goes from the coil negative to the • For general purpose testing the frequency accuracy is good enough. If you had a signal source of known accuracy and you were willing to tweak the timing components associated with IC11 (the 555), you could get the accuracy to better than 1%. Car stereo project wanted I am currently doing a pre-apprenticeship in electrical and we points and use the kit connections instead? If so, and I have tried this, the car doesn’t start! I have also tried it without the tacho connected but that made no difference. Can you please assist me? (T. G., via email). • The existing negative lead from the points should be discon­nected from the points. The points wire is then connected to the High Energy Ignition (HEI) input and the output from the HEI goes to the coil negative. In other words, the wire from the points in the distributor is used to trigger the HEI system and the HEI output now does the switching job for the coil primary that used to be done by the points. Probably the problem you are having is that the second set of components for the points 2 circuit is in circuit. If you are only using one set of points, remove diode D2 and the 47Ω 5W resistor next to this diode. The tachometer connection can be made to the tachometer output on the HEI or left in its original position if this oper­ates it correctly. are allowed to build a project of our own choice. I was won­dering if you could suggest a project design for a 300-400W RMS car stereo amplifier? (Justin, via email). • We have not published any 300 to 400W car stereo systems as a DIY project would be more expensive than a built-up unit such as those stocked by Jaycar. However, we have published a 600W inverter for car sound systems in October & November 1996 (Jaycar kit) and a 350W amplifier module in the August 1996 issue (Al­tronics kit). We can supply back issues at $7 each including postage. Video-audio transmitter causes picture roll I recently purchased a video-audio transmitter kit, as described in the July 1999 issue, from Jaycar Electronics. I have a picture coming through onto my monitor but unfortunately it rolls all the time. Can you suggest a cure? (J. B., via email). • The rolling suggests that the sync level is too low for the monitor to lock and maintain a steady picture. This could be due to the levels on VR1 and VR2 not being set correctly. It is recommended that both VR1 and VR2 be initially set fully clock­wise so that the maximum signal level is applied to the modula­tor. The picture may be a little washed out (excessively bright) but the locking problem should be cured. Then wind VR1 back for best contrast without rolling. Then set VR2 for best contrast if necessary. If the picture cannot be made to lock with full clockwise settings for VR1 and VR2, then it is possible that the 470µF capacitors have been inserted incorrectly. Alternatively, one of them could be faulty. Notes & Errata LED Christmas Tree, November 1999: three 0.1µF monolithic capacitors are required, not two as specified in the parts list. One of these (C6) is not identified on the PC board component diagram but is adjacent to pin 1 of the microcontroller. Also the PC board overlay shows two 15pF capacitors but these should be 27pF as shown on the circuit and parts list. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. 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