After realising what's involved in repairing his micro, Mark Smiddy decides to leave it to the expert technicians

Today's computers are, to say the least, very complex. Printed circuit boards packed with custom chips, dozens of discrete components and thousands of connections. The Electron is no exception. At its heart beats the 6502 8-bit microprocessor surrounded by a box full of support chips - and custom-designed monsters like the ULA.

With this sort of complexity, it's surprising how reliable the Electron is, but on rare occasions something fails, even with the extremely sophisticated quality control systems used by Acorn. So what do you do if it does go wrong?

The problem lies in the fact that computers are integrated machines, and if one tiny part fails, the whole machine is quite likely to go dead. No matter how competent you are with a soldering iron and a multimeter, fishing around willy-nilly inside the case is almost certain to result in more damage than was initially present.

There are two answers: Take it to a repair shop and get charged an arm and both legs for replacing a burnt out bridge rectifier, or find the fault and fix it yourself - properly. I'm not suggesting you do this without guidance of course, and this is where Michael Tooley's book comes in.

Right from the word "phut" - before you pick up your tools - the book gives the budding repairman a lesson in what he is about to fix. The first chapter contains a technical description of how computers work - at electronic level. This is fairly heavy going and not for the faint-hearted, but it is vital the principles are understood, in part at least, before any repairs are attempted.

Topics covered include simple microprocessor block and timing diagrams, logic paths, multiplexing, MOS technology, programming, input/output including a full RS232 set-up, and raster scan displays. Also to be found here are the full pin-outs of several microprocessors including the 6502 and most of the common support chips. For the more important chips, each pin-out has been given a clear description.

And if that was not enough, there's a vast number of diagrams showing parts of working systems - address decoding, for instance. Even though not all of this appertains to the Electron, the book explains the principals - after all, that's what counts.

If the first chapter is meant to put you off intellectually, the second must surely be designed to give your bank manager heart-failure. Seriously though, it talks of equipping your workshop with the correct tools and test gear, some of which can run into hundreds of pounds, although they can usually be borrowed from another friendly electronics buff.

Not content with just listing the required tools, the author includes examples of their use and what readings to expect.

The next 41 pages are spent on an essential skill in repair work - fault diagnosis. This starts once again with the principles of the technique and quickly marches through individual test procedures - how to do them, what to poke and what reading to expect while you're poking it.

Chapter four covers disc drive faults in great detail and concludes with a superb fault diagnosis guide. Likewise, chapter five includes full test, fault diagnosis and repair of printers and monitors.

The section on monitors is a little lacking for colour systems and TVs. That said, messing around in monitors should only be done if you're aware of the lethal voltages inside the case. The basic safety rules are not emphasised enough here.

The whole thing concludes with a nice, but not altogether concise reference section, most of the contents being reiterated in the better electronic supply catalogues like Maplin and Radio Spares. The index is better than average - listing references to part numbers as well as the usual buzz words.

This is not the sort of book for a bedtime read - nor is it meant for a complete beginner. However, anyone with some knowledge of electronics should be able to grasp most of the text fairly easily. If nothing else, it might show you that fixing your Electron is a job that really should be left to an expert.

For anyone at college studying for an ONC or higher in computing, this book is highly recommended.