Repair Amplifier 20220818 14 42 20 Pro

This is one of three amplifiers at the church I go to. I was gathering interconnection information for the whole system so I could make changes to improve reliability in Toowoomba's summer thunderstorm season when I found this had stopped working. I removed it from the equipment rack and took off the cover. There was nothing obvious except the blown fuse in the mains power socket. This photo was taken then. I replaced the cover and took it home for further investigation.

At home I eventually decided that the mains power transformer, the circular object with the wires going from it, was probably faulty. I contacted the Australian agent of the manufacturer, Bosch, for circuit diagrams and technical information. They weren't very helpful but did refer me to a business which did warranty repairs for this type of product. The service manager answered some general questions but didn't/wouldn't supply any circuit information. I worked out a likely AC supply voltage but didn't anything on hand to provide it to check that the rest of the amplifier was working correctly. I ordered a replacement transformer anyway with some trepidation. A pleasant surprise was that it was priced comparably with the normal pricing for similar transformers.

About a month later the transformer arrived. With the aid of some photos, a soldering iron and some other tools I replaced the transformer and was relieved when the amplifier then worked correctly. I measured a few key voltages and wrote them on the chassis in case there was any further trouble. The amplifier worked correctly when reinstalled in the rack at church.

Mouse-over to see some other photos of the amplifier.