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but this circuit will do the job. Make sure you connect pins 14 and 7 of the 74C14 to the supply lines of the 3-digit counter project. Speed control for a golf buggy Notes & errata Stereo Preamplifier with IR Remote Control; September, October and November 1993: on some units, the bass control is liable to become noisy and produce a scratchy sound from the loudspeakers when it is rotated. This problem is caused by a small DC voltage which appears across the bass control pot. This voltage is developed by the input bias current to pin 2 of IC6 and IC106. To prevent this problem, we recommend replacing IC6 and IC106 with OP27GP or LM627 op amps. These have signifi­ cantly lower input bias currents than the NE5534 op amps specified originally. Note that the 10pF capacitors between pins 5 and 8 for both IC6 and IC106 should be removed from the PC board since the replacement op amps are internally compensated. Finally, some early kits from Jaycar may have problems with the remote control not operating. The problem is due to a short between ceramic resonator X2 (on the main PC board) and ground, which prevents the oscillator inside IC23 from functioning. To cure the problem, go to the 4.7kΩ resistor side of the X2 pad and cut the copper between this pad and the adjacent ground track with a sharp utility knife. The problem has been corrected SC on later kits. SILICON CHIP FLOPPY INDEX WITH FILE VIEWER Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. Now you can search through all the articles ever published for the one you want. Whether it is a feature article, a project, a circuit notebook item, or a major product review, it doesn’t matter; they are all there for you to browse through. The index comes as an ASCII file on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers and you can use a word processor or our special file viewer to search for keywords. Now with handy file viewer: the Silicon Chip Floppy Index now comes with a file viewer which makes searching for that article or project so much easier. You can look at the index line by line or page by page for quick browsing, or you can make use of the search function. Simply enter in a keyword(s) and the index will quickly find all the relevant entries. All commands are listed on the screen, so you’ll always know what to do next. Note: requires CGA, EGA or VGA graphics card, IBM-compatible PC, MSDOS 3.3 and above. Disc size:   ❏ 3.5-inch disc   ❏ 5.25-inch disc ❏ ❏ ❏ ❏ ❏ ❏ ❏ Floppy Index (incl. file viewer): $A7 + p&p Notes & Errata (incl. file viewer): $A7 + p&p Bytefree.bas /obj / exe (Computer Bits, May 1994): $A7 + p&p Alphanumeric LCD Demo Board Software (May 1993): $A7 + p&p Stepper Motor Controller Software (January 1994): $A7 + p&p Printer Status Indicator Software (January 1994): $A7 + p&p Switchers Made Simple – Design Software (March 1994): $A12 + p&p Note: Aust, NZ & PNG please add $A3 (elsewhere $A5) for p&p with your order Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­_________________________ Card expiry date______/______ Name _____________________________________________________ PLEASE PRINT Street _____________________________________________________ Suburb/town __________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 979 6503; or ring (02) 979 5644 and quote your credit card number (Bankcard, Visacard or Mastercard). ✂ I have a golf buggy which is driven by two 12V electric DC motors marked SWN 402-400V 12V/23, with one motor on each wheel. What I require is a circuit to control these motors. (G. R., Tura Beach, NSW). • The most practical approach would probably be to use the DC speed control published in our November & December 1992 issues. Unfortunately, we do not have any back copies of these issues but we can send you a photostat copy of the articles for $6 each including postage. You can also purchase a kit for the controller from Silvertone Electronics – phone (02) 533 3517. April 1994  93