Well, its been a week of both frustration and success. Firstly discovered that my computer power supply wasn't pumping out the required voltage. I had been waiting for a couple of 10W resistors to turn up to help "load" the supply so hadn't really tested it so far (up to just confirming it turned on). Well, turns out it didn't need the resistors. After plugging one in the power supply promptly dropped 3volts and then shut down. Did a bit of playing around and eventually decided to open it up and have a look inside. Found a suspicious looking pot so gave it a tweak and low and behold, 5v and 12v on the rail. Happy dance. As the power supply can provide up to 18amp on the 12v rail I thought it prudent to add some form of protection in. I will eventually build a fuse box with mini fuses, but whilst I wait for them to turn up I used a simple glass 2A fuse and holder. Feel like I spend a lot of time waiting for stuff to turn up in the post - between lockdown's and the lack of decent swiss electrical shops I usually end up purchasing stuff from overseas. Took said power supply downstairs, along with newly build DCC++ system and Raspberry Pi with a fresh install of JMRI. Plugged everything and poof, smoke. After a bit of swearing, I took the Pi back upstairs for some damage assessment. Thankfully all I did was fry the SD card, and after installing a new card everything was working again. Another happy dance. Did a bit of soul searching to figure out what had gone wrong and came to the conclusion I had overloaded the Pi, it was trying to supply 5v for the onboard fan, power the DCC++ arduino and its onboard fan, plus power the 485 bus. So wired up a dedicated 5v supply to the DCC and used the 5v ring supply to power the 485 bus. With crossed fingers I plugged the Pi in and it booted up. Once I was happy and connected wireless on the iPad I fired up the power supply to the layout and everything burst into life! Big happy dance - I'm sure the neighbours thought I was having a disco. So for the first time in over a month the layout was placed back on the legs and I was able to start running trains again! All up I had three loco's running around with sound on and was pulling about .5A so well within the limits of the motorshield.