[high_vacuum_house]

Good evening,
A quick restoration this afternoon as the weather was bad. This time it was a Hornby railway power controller from the mid 1980's

I purchased this to make up a model railway layout and upon power up was completely dead from the variable supply to the tracks. Tapping it and wiggling the switches would make it cause brief spurt of power.

It is a vey simple supply with 15V AC output for signals and point motors and a variable DC supply for the track to run locomotives. The power switch really just switches the bridge rectifier from half wave to full wave supply. The speed controller is little more than an in-house made wirewound resistor.

To open it 6 rivets have to be drilled out of the case, the 2 switch dollys need removing and the power knob removing as well.

The 2 switches (one for direction change and one for low and high power) are not a bought in part from a component supplier, but made in house and are easily disassembled.

Here was the cause of the almost dead supply. The switch sliding contacts were brass strips and tarnished. This came up well with some Brasso. The other major problem was with the springing of the moving contacts. The sponge strips they used had deteriorated over many years and had lost all of its springiness so that the contacts were not being pressed onto the fixed contacts. I found some silicone sleeving was an ideal replacement for the old sponge and once fitted into the contact carrier, the sliding contacts were making good contact with their fixed contacts. You can see the difference in the third picture.

After cleaning the case, switch dollys and the power knob, reassembly was straightforward and I replaced the drilled out rivets with 4BA nuts bolts and washers to complete the work. The power controller now functions faultlessly now.