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.

Beocord 9000: Displays and Lamps

I left this Beocord 9000 project off waiting for some Beolover displays to arrive and preparing to give the beocord a quick functional check to see if it records and plays cassette tapes. I am happy to report the replacement lamps have arrived and my record/playback tests also worked. Once I finish the displays I will go through some organized cassette functional tests and show the results.

The display work can all be done with the Microcomputer and Display board in place inside the Beocord. Here are the display components looking from the top (so you can see the PPM scale lamp clearly).

I shouldn't have to touch the PPM displays other than the PPM Scale Lamp. I will replace the scale lamp and the indicator lamps with the LED replacement modules I got from Beolover. The 7 segment display will be disassembled, the original LEDs will be removed and modern surface mount LEDs will be installed in their place. Here is another picture of the Beocord 9000 as one would normally view the Beocord.

The first lamp to get replaced is the PPM Scale Lamp. Beolover originally posted the installation of one of these in the Summer of 2015. As mentioned on that thread, the Beolover tonearm position indicator LED replacement module can be re-purposed for the Beocord 9000 PPM scale lamp. Here is the part as I received it from Beolover.

As shown on the 2015 Beolover thread, the replacement is very straight forward. I like drop in replacements. This sequence of pictures shows the replacement.

This picture shows the Beolover replacement lamp modules for the four indicator lamps. There is also a 2015 Beolover thread on this subject.

The above picture also shows the seven segment display has been removed. It is time to prepare that part for restoration. Here is what the seven segment display module looks like taken apart.

This is a better shot of the seven segment display LED board (front and back).

The smallest dots on the display are the original lamps. This picture shows that each lamp has a tiny wire strand on one end of the display lamp. That delicate wire can be broken or about to break.

I will continue this seven segement display module restoration in the next post.

Beomaster 8000 Display Repair

Another Beomaster 8000 display repair marathon. I must have soldered about 280 SMD LEDs by now into these displays (it takes about 70 LEDs and this is my fourth display...;-). I basically repeated what I described in: http://beolover.blogspot.com/2012/09/beomaster-8000-display-repair-hopefully.html
Here is a pic of the outcome. I put them into my display test breadboards and ran them at 2V (~0.53 Amp):

All segments are present. It is a good idea to do a mechanical test while the LEDs are out in the open. I give them a pretty good push and pull with a toothpick in all directions to make sure they have good contact. Since there is no solder mask the solder has a tendency to distribute on the pads, and it can be difficult to create a decent solder bump at the contact pads. Inspection with a magnifying glass is also a good idea to make sure they are aligned and centered precisely. If they are not it is difficult to get the bezels back on in a way that they block the light laterally (if the bezels are not set well and there are gaps, then light enters adjacent segments and in a dark room this can be seen...not acceptable for the beolover!). Now I will give them a 'burn in' over night and then mount the covers back on. this Beomaster 8000 is hopefully soon ready for a test in the living room!