I began troubleshooting the Beocord’s electrical issues by examining the power supply. The power supply wasn’t functioning correctly, and I wasn’t getting +24 VDC at capacitor C1. Initially, I suspected the rectifier board, so I removed it to inspect the supply capacitors (C1, C2, and C3).

Here are the readings for capacitors C1 through C3.

To further diagnose the problem, I swapped components from other Beocord 9000 units I had available. The rectifier board from this Beocord worked correctly in a different, functioning Beocord, confirming that the board was not the issue. This pointed towards a potential problem with the transformer. Upon testing, the transformer indeed proved to be the source of the problem.

Initially believing the transformer to be faulty, I began inspecting transformers from other Beocord 9000 units, both working and non-working, that I had on hand. I discovered another unit with a non-functional transformer and noticed something interesting when I compared its serial number to the Beocord I was actively repairing. Surprisingly, the two Beocord 9000 units had sequential serial numbers, suggesting they were manufactured consecutively. The odds of these two units ending up on my workbench after all these years were remarkable.

However, the transformer itself turned out to be fine. I recalled that the transformer assemblies have an internal 250V, 0.5mA fuse. I opened both transformers, and as expected, the fuses were blown.

Replacing the fuses resolved the power supply problems in the Beocord 9000. Now, I need to determine why the unit is still not powering on.