The refurbishment process starts with a basic inspection of the computer as received. Many of these computers have indelible security markings, badly scratched or broken cases, damaged or missing keys, etc. and in those cases a decision is made as to whether the computer should be scrapped, broken up for spares, sold as a B Grade refurbishment, or imply sold on as an ‘as found’ system.
For the purposes of this article, we are assuming the computer is in good cosmetic condition and suitable for a full refurbishment.
After the initial cosmetic inspection, the next step is to remove the top cover to inspect the computer inside.
In this case, the circuit board is reasonably clean and has been fitted with an aftermarket RAM board and disk interface.
Before staring refurbishment work, the internal power supply is disconnected and the system board connected up to my BBC Test Station. This supplies the correct power requirements, but has protection in case of short circuits, excessive current draw, etc.
The machine has started correctly, so no further work is immediately required. In cases where the machine fails to bring up the start screen, an appraisal is made as to where in the refurbishment process the board should be repaired. Most faults can be diagnosed with the aid of my BBC Test Station and an Oscilloscope, but I also have a range of other test equipment I can use when required.
At this time I also give the keyboard a quick test to ensure that at least some keys are working. A full test will be made later in the process.
The next stage is to remove any aftermarket add-ons. In many cases these will have been fitted by end users, and the quality of the work done is variable. In the case of the sample machine here, the RAM board was soldered to various points on the system board, and one joint had broken off completely, while several others were very close to bridging adjacent pins on the ICs that the cables had been soldered to. Rather than complicating the refurbishment process by attempting to repair any faulty wiring etc. I will remove all such add-ons to to bring the computer back to its original specification.
Removed add-on components will be appraised later and either fitted back to this or another machine where appropriate, sold on separately, or scrapped according to type, condition, etc.
The refurbishment process is split into multiple parts – I normally start with the power supply. In all cases, the first job with these is to replace the old RIFA interference suppression capacitors as they are prone to failure and often explode on switch-on giving a loud bang, smoke, and an unpleasant smell.
At the same time I always replace the startup electrolytic capacitor as it is also very prone to failure (though not in so dramatic a fashion).
While the power supply is dismantled, I take the opportunity to check it thoroughly , remaking joints and replacing other components where necessary.
Good quality parts are always used to ensure that the power supply will carry on working for many years to come.
The mains cable is also replaced with a new strain relief grommet and a new 3A fused mains plug.
Finally the power supply board is refitted to its case and all screws, cable ties etc. replaced.
The final stage of the power supply refurbishment is to test it using my BBC Test Station to ensure there are no problems.
Attention now turns to the main system board which is removed from the case, visually inspected, and cleaned. In this case I noticed a poorly fitted integrated circuit. This appears to have been a manufacturing error as there were no signs of rework to the chip’s legs.
As several of the pins hadn’t even gone through the board I decided to replace this component as relying on a tiny piece of solder to keep everything working seems to be a risk not worth taking.
Unless parts are rare, I normally replace with new – even when, as in this case, there isn’t a known fault. This means I can use removal methods for the component that damage the chip rather than risk damaging the board.
Other work on the board done at the same time includes checking all jumpers are in the default positions, and where a disk interface had been fitted and a wire link cut, a new connector and jumper fitted to allow a simple change in the future if a new disk interface should be added.
At this time I also give the main board a thorough test and rectify any faults that may show up.
Attention now turns to the keyboard which is stripped of all its keys ready for cleaning.
After cleaning, the keyboard is reassembled.
The case is fully cleaned and the computer is then ready for reassembly. I often find that there are missing screws, washers, etc. and sometimes the wrong ones have been fitted. This seems more common in computers that have been used in schools, but I keep a good stock of spares and replace them where required.
The finished computer.
The final step, and probably the most important, is to run a series of tests to ensure I haven’t missed anything.
The test program has been written by me and tests the main parts of the computer to ensure everything works reliably.
A final soak test repeats a number of the tests on a loop to ensure there are no issues with the computer remaining on for an extended time. I usually run this for about 2-3 hours.
Assuming everything is working correctly, any upgrades are fitted and tested before the computer is carefully packed ready for despatch to the buyer.
