Some years ago, a friend of ours had a large house fitted with security sun blinds. These are all remote controlled and block out the sun as well as the burglars.

In all, there are 17 of these babies installed, some as large as 2 x 2m. They look great, are easy to use and work quietly and efficiently. What’s more, you can control each window or door shutter individually or all simultaneously with a master remote control.

The only problem was that these had now all stopped working. And because they would be very expensive to replace, I volunteered to see if I could help.

The first problem we encountered was how to disassemble them, as there were no service manuals available. That meant that we had to figure it out as we proceeded.

Removing four rusty screws from the top cover gives access to the top of the roller shutter. We then found that when 240V power was applied to the blind, it would emit a whistling noise but nothing else happened.

We then discovered that there was one rivet at one end which had to be removed and we did this by drilling it out. This rivet can be at either end, depending on whether the motor is at the lefthand end or the righthand end. Once it’s removed, you can push the plastic end in, drop the motor case off its axle and let it drop out of its case.

Next, making sure that the 240V is off, you remove a Philips screw on the other end to release a plastic core. This is then slid out, after which you can unplug the motor and power input and remove a clear plastic tube containing the control electronics. This consists of two interconnected PC boards – one is the RF remote control receiver, while the other is the power supply and controller.

Now that we had the boards out on the bench, it was time to find out what was wrong. Both were double-sided boards with surface-mounted components and were nicely made.