Beogram 8000: Display Segments Working Again

When I was able to finally check the recapped electrical work I discovered the bottom segment of the seven segment displays was not working. That usually is a connection problem (like a bad solder joint) but it could also mean a problem with the 4.7nF capacitors on the display driver circuit. In the case of the bottom display segment, C41.

Here is the failed segment on the Beogram display.

Here is the schematic portion for the Beogram display.

The display driver circuit is located on the microcomputer PCB. That board is small and the solder pads are very close together.

You can see that there are several solder pads on the component side. The 4.7nF capacitors here have one lead soldered to the trace side and the other to the component side. The pad on the component side is very difficult to get to with the surrounding components in place. The best thing to do is to remove all of the components in the area of the 4.7nF capacitors including the display cable.

On the trace side of the board I found some failing solder pads. One damaged pad is on R21 which corresponds to the bottom display segment (d).  The solder pad immediately to the left of it is also starting to come loose so I have two solder pads to repair.

Since I have the display driver components removed I will go ahead and replace the old 4.7nF capacitors with new ones while I am repairing the connection at the failed solder pad.

Here are the new capacitors, the original resistors, the TR1 transistor and the display cable re-installed.

The trace side shows where I bridged the failed solder pad connections.

Now I can re-assemble the Beogram components and check the display again.

The bottom segment is working again.  Now on to the platter detection circuit problem.