Hope this is helpful below: https://uk.hornby.com/community/forum/hornby-class-50-r2350?ccm_paging_p=5&ccm_order_by=&ccm_order_by_direction= This original link above may provide some useful information with regards to discussion on the Class 50 and converting to DCC. My own personal experience (detailed below from back in 2017) sorted the issue by simply buying a X9788 PCB for a Class 56: Details below: http://www.petersspares.com/hornby-x9788-class-56-main-pcb-board.ir This PCB (X9788 for a Class 56) does indeed definitely work perfectly, in the original Hornby Class 50 (R2350). My loco came out the Hornby factory with a short circuit on the original fit PCB. Despite recently (2017) talking with Hornby, they no longer have the ‘modified’ PCB version available, so could offer no solution, other than sending the loco to them for them to await a donor part to become available. The loco and lighting work just fine on DC, but as soon as you remove the blanking plate and put a DCC decoder in, the DCC controller then short circuits. Turning the decoder 180 degrees doesn’t make any difference either. As I didn’t want to blow the chip up, I removed it! The PCB does need to be the exact one shown in your photo (X9788) with the black jumpers at either end. There is a second later version of the X9788 with white pre wired connectors either, which isn’t suitable and clearly is different. As my Class 50 is now running perfectly, I thought this information may help others.