Class 33

Updated on 4 December 2016

I have two Heljan Class 33s. One is all green and will probably be D6506. The other is green with small yellow panels and will probably be D6545. I fitted sound decoders to both of them but I never managed to get the fans working properly.

Last week the final drive gear in D6506 split so I sent for a replacement from Howes. Having successfully replaced the split gear it occurred to me that the fans in my Heljan Western work fine. I bought this with DCC already installed so I took the top off to see how it works.

The Western has a separate board for driving the fans. It is connected between an AUX output on the decoder and the fans and is shown below.

The components used on this board also appear on the class 33 board so I compared the circuits and concluded that I could cut the appropriate circuit away from the class 33 board as shown below.

I removed the components that were not required. That made it easier to neatly cut down the board. I was careful not to cut into the tracks needed at the edge as shown here.

The wires to the bottom go to the fan. I had removed the connector. The wires to the side go to the AUX and common connectors on the decoder.

I have followed this success with a similar exercise on the Class 47.