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Want to boot a PC without a keyboard but it refuses unless the keyboard is connected? You can usually overcome this problem by altering a BIOS setting but not all BIOSes let you do that. Here’s a simple low-cost way to “fake” the keyboard and make the PC boot. By GREG SWAIN T here are many situations where it’s convenient to have a PC running without a keyboard or monitor connected. For example, you might have a network PC that functions as a dedicated Inter­net gateway or as a file and printer server. Or perhaps you have an old PC that controls a watering system or security lights around your home. In those cases, you usually leave the PC running continu­ously – perhaps stacked on a shelf or tucked out of sight in a cupboard or in the garage. And because the machine isn’t being accessed, you don’t want a keyboard or monitor hogging valuable space. Nearly all PCs will boot without a monitor but will “hang” if there’s no keyboard. Fortunately, that’s usually easy to fix – just go to the main menu in the BIOS setup and change the “Halt On [All Errors]” setting to “Halt On [No Errors]”. That way, when the machine starts to boot, it will ignore any errors that are detected during the boot process, such as a missing keyboard. This keyboard incorporates the key contacts, scanning matrix and control circuitry all on one large PC board. In this case, it’s just a matter of cutting out the control circuitry (inside the dotted yellow line) and discarding the rest. 76  Silicon Chip The BIOS is usually accessed by pressing the “Delete” key when prompted, just after the computer has completed its POST (Power-On Self Test) routine. In some cases, however, you have to press the F1 key or some other key to access the BIOS, although this is usually confined to older machines. No BIOS setting OK, that’s the easy way of doing it. But what if no “Halt On” setting is included in the system BIOS, as in some older (and not so old) machines? In that case, the only way around the problem – short of hanging a real keyboard out the back – is to use a “dummy” keyboard. It’s quite simple really – just obtain a defunct keyboard, “rat” the electronic circuit board from it, whack it in a small case complete with the cable, plug it into the PC and Bob’s your aunt. The bulky keyboard that you were hoarding “just in case it came in handy” can then be chucked in the bin (where it really belongs). As long as the PC “sees” the relevant return codes from the keyboard circuitry, it will think that a real keyboard has been connected and will boot up. Of course, this assumes that the circuitry itself is OK. Fortunately, this is almost always the case – it’s the key con­tacts that usually fail. Either that, or the keyboard becomes so grotty and full of muck that it’s replaced rather than cleaned. By the way, the “dummy” keyboard idea isn’t ours. We origi­nally saw it posted on the local aus.electronics newsgroup by Franc Zabkar and pinched it – with Franc’s blessing. Removing the PC board Usually, the circuit board is quite www.siliconchip.com.au This keyboard has the control circuitry on a separate small PC board and it’s easily removed by undoing two screws. Subscribe & Get this FREE!* *Australia only. Offer valid only while stocks last. Once the screws have been removed, the key matrix membrane is unplugged from the edge connectors on the PC board. After removing the PC board, it was necessary to reattach the cable braid (which provides shielding) to the earth track using a 6BA machine screw, washer and nut (shown arrowed). compact (it’s invari­ ably based on a single chip) and it has an edge connector for a key matrix membrane. You don’t need any of the keys, so it’s just a matter of removing the keyboard back, undoing a couple of screws to remove the circuit board and unplugging the key matrix membrane. The NUM Lock, Caps Lock and Scroll Lock indicator LEDs can also be removed. You should be left with the circuit board itself plus the cord that’s conwww.siliconchip.com.au nects it to the PC. This can then be housed in a small plastic case, fitted into a plastic tube or, if it’s small enough, encapsulated in some heatshrink tubing. Any excess cord can either be stuffed into the case with the circuit board or neatly coiled up and secured with tape or cable ties. The board’s too big Instead of a key-contact membrane, many early keyboards were based on THAT’S RIGHT – buy a 1- or 2-year subscription to SILICON CHIP magazine and we’ll mail you a free copy of “Computer Omnibus”. Includes articles on troubleshooting your PC, installing and setting up computer networks, hard disk drive upgrades, clean installing Windows 98, CPU upgrades, a basic introduction to Linux plus much more. Subscribe now by using the handy order form in this issue or call (02) 9979 5644, 8.30-5.30 Mon-Fri with your credit card details. Silicon Chip Binders REAL VALUE AT $12.95 PLUS P &P AUST. ONLY Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. February 2002  77 VGA Pin Connections The board was too long to fit into the case we wanted to use, so we cut it in half using a hacksaw (cunning, what?). The two sections were then joined using rainbow cable. Note that we only needed a 4-way cable for this – the tracks running off to the edge connectors for the key matrix aren’t required, so they don’t need to be joined. one large PC board which included all the circuitry plus the key contacts and scanning matrix – see photo. In this case, it’s simply a matter of using a hacksaw to cut away the wanted section containing just the electronics. It’s really just a matter of using your commonsense as to what you keep. Obviously, you need to keep the chip plus all the circuitry (including the supply tracks) between it and the cord. You don’t need anything that runs off to the keys or to the indica­tor LEDs. If an AT/XT switch is present, leave it in place and switch it to the AT position. Practising what’s preached To demonstrate how easy it all is, we ratted an old AT/XT keyboard. Its circuit board proved a bit too long for the small case that we wanted to use so we cut it in half using a hacksaw and then joined the two halves using some rainbow cable. This allowed the two halves to be (REAR OF PLUG) 15 14 13 12 11 10 9 8 7 6 5 4 2 75 1 75 folded over and squashed into the case, with some heatshrink tubing over one section to prevent shorts. A slot cut into one of the case ends provided the exit for the cord which was neatly coiled up and secured with a few cable ties. What about a monitor? It’s only rare that not having a monitor causes boot prob­lems but some old VGA video cards (eg, Trident) can The thin section of board was insulated using heatshrink tubing and “folded” back over the main section. The cord exits through a slot cut into one end of the case. 78  Silicon Chip 75 3 Fig.1: three 75Ω resistors wired to the back of a DB15 VGA plug is the cure if the PC won’t boot without a monitor. Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Connection R ed Green/Mono B l ue R-Gnd G-Gnd B-Gnd Gnd Gnd (C ol our) Hor. Sync Ver t. Sync - be fussy. Franc Zabkar’s suggestion here is to connect three 75Ω resistors between each of the RGB outputs and their respective grounds. The above table shows the pinouts for the VGA connector, while Fig.1 shows how the three resistors are wired across the back of the plug. You can pick up a DB15 VGA plug (plus plastic shell) from an electronics supplier for a few dollars or scrounge one for “nix” SC from a defunct monitor. At 120 x 60 x 28mm, the dummy keyboard is a lot smaller than the real thing. It can be affixed to the back of the PC (eg, using Velcro) or perhaps even hidden inside the PC. www.siliconchip.com.au