The Most Famous Five Faults on the Atari

R. Harrison guides us through ways of remedying the commonest five hardware faults that afflict users of Atari machines....

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The most common hardware faults on the ST are all listed below. To fix them it is necessary to have the machine completely stripped down in front of you — and isn't there a lot of tin plate to remove! I absolutely detest stripping down STe machines and remember vividly the first time I did so. I had been well used to diving into STFM's and was completely taken aback to discover how many extra bits of metal there were that had to be removed. There was one screw on the power supply that eluded me for half an hour! Be warned. To gain access to it you will have to have the lower half of the case completely separated. The order for disassembly goes:

Plastic case: 7 screws in total. The front case screws are shorter so take note. Remove STe's from case completely at this stage.
Unplug keyboard. The plug only fits in one way round so you can do this with confidence.
Disk Drive. Three screws travelling through glued plastic pillars. However there is also a fourth pillar made of brass which needs lifting out and putting somewhere safe with the screws. "Somewhere safe" should not be down the back of a sofa, inside a goat, or on the fifth moon of Targus — but usually is. In addition it is a well known fact that there are gateways to a parallel universe that open up at such times and through which all the known useful screws in our world are destined to disappear. Even Captain Kirk won't be able to save you. You have been warned!
Power Supply. 2 screws on the board on an STFM. There is an extra bolt on STe's next to the switch. Now, you have unplugged the machine, haven't you, because — and many people forget this — if you haven't, even with the power switch off, there are still roughly 240 volts and a sizable number of amps lurking on the switch contacts ready to take the short route to the centre of the earth via your nose, or anything else you might be using in the machine at the time.
Metal Shielding. Loads of screws and bolts. STe owners — suffer! If you plan to take further weekend trips away to the interior of your machine, then take the opportunity of cutting two sections of tin plate away permanently. One of these is the piece that runs under the disk drive. The other is the piece that obstructs the power supply. Next time you go exploring just remove both the plastic and metal covers and hey presto — you're in! So there you have it. One stripped machine. Not quite as pleasing as Kim Basinger, but there you go.

Famous Fault #1

The most famous fault of all is the infamous one by which the power light comes on but nothing happens. Such machines closely resemble many office managers of my acquaintance and appear to be totally useless. However, the solution is well known. Look carefully and see if you can find a square socketed chip with either the number C025912 or C0100109 written on it. This chip may well be in a socket and is known as the MMU (Memory Management Unit). It is this device that is usually responsible for any amnesia in an Atari. If yours is a surface mounting device then your problem lies elsewhere. However, if it is socketed then take note that the springs on these sockets cause many problems. They are usually made of cheap metal and their contacts fail with the passage of time. This can vary from thirty minutes to thirty years. Carefully insert a compass point down the socket's corners and lift the chip 2-3mm up in its socket. You may well have to remove a couple of brass clips in order to do so. Replace the PSU and the disk drive and see if the machine boots.

If it doesn't then proceed as follows. Lift the board out completely and locate both a helpful child and a multi-meter with an audible continuity tester. Strap a pin to one of the meter's test probes. Go round testing every pin of the MMU socket on the board side and use the pin to contact directly with the springs on the MMU chip. The chances are that amazingly there is still a bad contact there. If there isn't, do the same for the GLUE chip. If there is a bad contact then gently remove the IC completely by working it out evenly from one side to the other. Then, carefully tease the springs out with a pin and replace the chip. Alternatively you can clean all of the springs with one of those useful little fibreglass pens that Maplins sell. Do try not to break any of the springs. These sockets are non-standard and cost between £10.00 — £12.00 each! You can, if you are rich and talented, remove the original socket completely and replace it with one with gold plated contacts.

However, if you have installed a Marpet STFM Memory Expansion Board then never, and I mean NEVER, remove the header plug that sits above the MMU. You will weaken most of the springs in the socket and instantly be reduced to teasing them back out with a pin.

This fault is extremely common amongst people who routinely cart their Atari's around from place to place — so musicians beware! I once worked with a guy who refused point blank to believe this and trekked his machine to and from work every day. His machine failed him four times in twelve months and still he wouldn't believe it. This stupidity cost him a lot of money.

Famous Fault #2

The power light does not come on. The power lead has been checked and found to be in perfect working order, and a sense of overwhelming despair has permeated the room.

This fault is usually related to the huge metal heat sink that runs from one side of the power supply board to the other. Now do be aware that this is also used by roughly 240 of those unfriendly and anti-social volt things as a means of legging it from one side of the board to the other, so if you subsequently plug the unit in and touch it you will instantly be used as a short cut.

I discovered this in the course of being assisted in the revival of a dead PSU by observing the demeanour of a world authority in the field of analogue to digital conversion who made exactly this mistake. The plethora of technical terms that spontaneously erupted from this venerable sage as the longest digit on his right hand hit the heatsink was quite remarkable. Sorry Doctor Unwitu!

However, the fact is that these heat sinks (unsurprisingly to some) get hot! Simply remake the solder joints on the transistor that is strapped to it and try again. Another well known problem used to centre around the first resistor called — you've guessed it — R1! These have to be a precise value and early PSUs had resistors whose value would stray with the passage of time.

Famous Fault #3

The floppy drive writes junk occasionally. It is the only one connected. There are no viruses present and yet the machine is spontaneously producing mysterious files that are zillions of bytes long with garbage names that cannot be erased.

This is most likely the disk drive ribbon cable. If you look carefully you will probably find that the disk drive has been replaced at some stage. This usually requires that the disk drive ribbon cable be twisted savagely through 180 degrees. If this is not done carefully then the contacts inside the transition header on the PCB become strained and eventually fail. Replace it with a section from an old printer lead.