In Stem land I was trying to repair a preamp which was not working. I opened it and I tried to find the problem. The problem was that the circuit wasn’t connected properly. I made the connection. The preamp needs an Ac input 9 V and 1A transformer. We bought the transformer and made a cover for the transformer in the Stem land with the 3D printer. The green box was made by 3D printer. Now the preamp works.