This is the controller....http://www.tri-ang.co.uk/OONew/Powerp4_5.htm
This is a very old controller and it needs to be very carefully inspected for any possible cable or case damage
Carefully inspect the mains cable especially at both the plug end and where the cable enters the controllers case. No splitting or other signs of deterioration or damage to the cable sheathing should be seen. Any damage spotted MUST render the controller immediately defective and it should not be used
Inspect the mains plug for any damage. If its ok then remove the plug top and inspect the connections inside - Red wire to the fuse side terminal. Black wire to the lower left and green to the top central earth pin (It is highly unlikely the cable will be of the modern colour coding of Brown, Blue and Green/Yellow unless its been replaced at some stage). All three wires should not be tight or be pulling on the terminals. All copper wire strands should be inside the terminals the grub screws tight and the insulation on each wire is right up to the terminal. The cord grip should be tight onto the cable sheath. If it is missing or isn't able to be tightened replace the plug with a new one. The fuse should be rated at 3Amp not 13Amp or any other rating over 3Amp! If all ok refit the plug top.
Assuming the mains cable and the plug are all in a 100% good condition, power up the controller. With a multimeter set to its dc volts range of 20 volts or higher connect the meters test leads to the Controlled pair of terminals (Left-hand pair of terminals). Turn the speed knob from its central Off position clockwise and the meter should show the dc volts increasing as the knob is turned further clockwise. If OK return knob to central Off and then turn it a little anti clockwise. The meter should show a small voltage and also show a reverse polarity from that previously read. Increase the speed knob further anti clockwise to eventually full and the meter should read somewhere between 12 to 20 volts dc without any load.
Also check the Uncontrolled dc output terminals (right hand pair) There should be 12 or slightly more volts continually on this pair of terminals regardless of the speed knobs setting.
If there is no voltage reading check the the small push button overload reset button located front top centre. Try pressing the button to see if it resets the controller and volts then are read.
If all the above fails to show any output DO NOT ATTEMPT ANY INTERNAL REPAIRS YOURSELF
Scrap the unit.
You can if your able, find a qualified Electrician and ask if they can examine the internal connections and components for you. But often the cost of them undertaking this work is just not worth it.