September 1995 FAQ When things don't seem to be going right with your Amiga, let CU Amiga show you what to do.. Q. When I switch my Amiga on the screen goes a funny colour. What's wrong? A. During the startup process (called "Booting") the Amiga performs a set of self-diagnostic checks. During these tests the screen changes colour and if anything serious goes wrong, the display may freeze. If all is well, the normal boot process continues and either the Kickstart display appears (the insert disk display) or the Amiga boots from harddisk or floppy. Here is a list of the screen colours which you may see during booting, including those which may appear if all is not well. Dark Grey Initial hardware and CPU test passed OK Light Gray Initial software test passed OK Red There is an error with the Kickstart ROM Green There is an error with the Chip RAM Blue There is an error in one the custom chips Yellow Trap error: something crashed before the Guru trapping code was in place. Sometimes the problems are due to loose chips or boards. For example, a Red screen may sometimes be fixed by pressing down on the Kickstart ROM to make sure it is seated correctly. Ocassionally "ROM switching" kits put too much strain on the ROM socket, and cause bad connections. Sometimes you can carefully remove the chip and straighten any bent pins (remember to use anti-static precautions). A Green screen could be caused by a loose memory board in the trapdoor socket, or a loose or faultly RAM chip on the expansion board. If you get the same result testing the board on another Amiga chances are a RAM chip is damaged and needs replaced: if soldered directly to the board this is best left to a dealer. Q. My computer seems to crash (Guru) a lot. What's happening? A. Rather than being a hardware fault, it is more likely that Gurus are caused by a particular program which requires more memory or a Floating Point Unit or some other resource which isn't present on your system. For example, Virtual Memory programs need an MMU: a Memory Management Unit. Some 68030's (but not all) have an MMU as an integral part of the processot chip. Slightly cheaper EC versions don't. MMUs are also required by debugging programs such as Enforcer. If your Amiga crashes when playing games which don't require any special resouces, or continually resets or pops up the Software Failure banner when nothing is happening, it could be an intermittant fault due to hardware. There are difficult to pin down, but common causes are faulty or overloader power supplies. Q. My disk drive seems to be faulty. When I put a bootable disk in (such as a coverdisk or game), it makes a few clicking sounds but then nothing happens. A. It could be the disk drive itself is broken. If you have Workbench 2 or better, you can check by using an external disk drive. Pop a disk in the extermal drive, and if the same thing happens then it is probably not the internal drive: it's more likely to be a problem with the CIA chip. If the external drive works, then there is a good chance the internal drive is broken. Symptons of a dodgey drive include: sometimes the disk will be recognised, sometimes it won't. Some disks will work, some won't. Depending on the severity of the problem it may be possible to ask a repair shop to recalibrate the drive. In the worst case the drive will need to be replaced, which will cost about £30 to £50. It isn't hard to fit a new floppy drive as long as you get the right model for your Amiga. Q. My A500 power supply is broken. Can I use the power supply which came with an A1200 with an A500? A. Yes you can. The leads are identical, and even if the A1200 supply is rated higher it will work fine. The A500 will only draw as much power as it needs. Q. When I switch on my Amiga, the caps-lock light flashes. What's up? A. The Amiga keyboard also has a self-diagnostic rountine, and it communicates by flashing the caps lock key. The warnings are as follows: One Blink Keyboard ROM error Two Blink Keyboard RAM error Three Blinks Timer failure If your keyboard starts to misbehave like this, there is very little you can do. You should check to see that all cabling is fitting tightly, but if the problems persist you will need a replacement keyboard. BOX OUT: CIA Chips The Amiga relies heavily on a chip called the CIA 8520 or Complex Interface Adapter. The chip is so useful there are actually two of them in every Amiga, and they handle the serial port, the joystick port, the mouse port, the disk drive, the printer port, the keyboard and various other timing duties. Unfortunately, it is also quite easy to break one or other of the chips. If you connect a printer cable, modem cable, external floppy drive or mouse to the Amiga without first switching off, you run the risk of damage. If your joystick fire button is broken, or your printer port doesn't work the CIA could be to fault. Similarly if your disk drive is refusing to work and the keyboard is playing up. On an A500 or A2000 replacing the chips is quite straightforward, but one of the first things you should try is swapping the chips over. To get at them you'll need to open up the case and remove the metal shielding. The CIA chips are both 40 pin chips and clearly labeled as CIA ODD and CIA EVEN. Swap the chips over (making sure you put them in the sockets the right way round) and see if the problem changes. If you are lucky, this might temporarily solve the problem: for example, if the CIA which looks after the disk drive is broken and you swap them around, the broken CIA is put in charge of the serial port -- and perhaps you don't need to use the serial port. The best solution of course is to buy a replacement chip. These cost about £15. If you have an A1200, then unfortunately replacing the CIA is beyond most home users as the chips are soldered directly to the motherboard. Unless skilled at such repairs, you will need to call in the repair person. They will either replace the chips or the motherboard and charge you about £40. Box out: Contacts Amiga repairs and spares are available from: Fast, Tel: 0171 252 3553 DART Computer Services, Tel: 0116 2470059. OmniDale Supplies, Tel: 01332 291219