Beocord 9000: Ready for Bench Testing

This weekend I completed the seven segment display rework. I didn't run into any problems with the LEDs during the twenty-four hour burn-in test. After re-assembly of the display I checked the LEDs again. My test jig has two sections for testing the Beocord display. The one shown on the left runs tests with every LED illuminated. The section on the right is when I want to check one LED channel at a time. Or I can check just one LED at a time if I move some jumpers.

During the individual display test I noticed there was a little bit of LED bleed through from the middle "dot" LEDs into the adjacent segments. This would be a noticeable thing when the Beocord is in standby mode.

I checked that all of the SMD LED components were centered in the light guide. The base of the guide was not resting on any part of the LED. Then I remembered this board has three trace repairs. The thin repair wire must be preventing a perfect mating of the light guide base to the board. To fix this I applied a thin coat of black automotive weatherstrip adhesive to the bottom (base) of the light guide. I made sure no adhesive could get into the LED slots. This was also a good thing because the three, white, plastic mounting pegs of the light guide had to be cut away to dis-assemble the display. This adhesive would now block bleed through light at the base as well as attach the light guide to the base. I apologize for not having any pictures of this step but the adhesive has too short of a working time to allow for stopping and taking photographs.

The result worked very well although the short work time of the adhesive made for some assembly stress on the repairman. To prevent any LED light bleed through anywhere else on the assembly I taped up the back as Beolover does on his display repairs. For the outer sides of the light guide though I added a coat of black 1-Shot enamel paint.

The final step was the mounting of the red display cap. I used black hot glue to secure the cap to the rest of the display.

Here is the result.

At the lower right of the picture above you can see the Beocord's lithium battery. That supplies offline power to save any cassette calibrations the user has stored in the Beocord. The battery is soldered to the board via a couple of solder tabs so it requires de-soldering and soldering to change. This battery measured okay but it is a good idea to change the battery install to use a battery holder. That makes changing the battery a much simpler job in the future and no worries about a battery explosion (when de-soldering).
Here is the reworked Beocord battery.

Now I can button up the Beocord and move it over to the test bench. I might still have some tweaks on the Beocord before I send it back to its owner but we'll see what comes up during testing.

This frees up my workbench so I can now start on the Beocord's master...as in Beomaster 8000. That will be the next step in this restoration work. I will do a quick check of the pre-restoration state of the electronics. Then I will start in on the work.

Beocord 9000: Seven Segment Display Board Reworked

It took a little longer than I expected to get my Beosystem display board rework station set up for doing repairs again but I finally got everything in place for repairing and testing the LED display. Here is my test setup for bench testing the display and running the burn-in test. I checked the setup with a working Beocord display.

Here is another look at the display board front and back. This time I have added markings for the segments and the polarities to follow.

There are thirty-one LEDs. This is what the original LED lights look like up close.

Here is the original LED compared next to the replacement SMD type LED.

To prepare the display board for the new SMD LED devices I will scrape off the old LEDs with a razor blade. I also discovered the new SMD LEDs solder in place better if the little pad the old LED rests on is removed.

That leaves the gap just right for the new LED device. Since I have quite a few Beosystem displays from this era waiting for repair I went ahead and ordered a reel of the replacement LEDs (Lumex SML-LX06031W-TR).

A little bit daunting when you first see how small those LEDs are. You must have magnifying equipment and SMD tweezers to work with these. Here is a picture of the Lumex SMD LEDs top and bottom.

I cannot see the cathode mark without the aid of a magnifying glass so I have to examine each one first as I pick it up with the tweezers. They are all oriented the same way in the reel packaging but I still double-check because I just want to make sure myself.

If you are just doing one display board then most people hold the SMD LED in place with tweezers and apply some solder with a soldering iron fitted with a small tip. I have done that before and it works well. However, I plan to do quite a few of these and with this Beocord display alone, that means sixty-two solder points.

Another option is to get an SMD rework station. I use an Aoyue SMD rework station.

The 853A is a heating system to preheat the board being soldered so you can lessen the amount of time the heat gun has to be applied to the board. I am currently using a temperature of around 180˚C.
After I let the board warm up, I use the 968A station heat gun at around 340˚C. I set the air flow on the heat gun to the minimum setting so none of the SMD components get moved out of position (by the heat gun air).

Here is the Beocord display board before and after processing with the heating station.

After that I cleaned the board with some isopropyl alcohol, examined with my magnifiers and checked continuity with a DMM. I found three bad board traces so I had to repair them with some thin magnet wire.
Finally, a successful board test.

I am going to leave the display board powered up in the test rig overnight to make sure everything is good. Tomorrow the display should be ready for full re-assembly and put back in the Beocord.
That will leave just a couple small tasks to do on this project and this Beocord will be done.

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.

Beocord 9000: Reassembly

With the recapping, cleaning and maintenance completed today was the day to put things back together in the Beocord and see where this project is at. I am starting with an empty shell since I removed everything out of the Beocord for the restoration. Although there are a few little tricks to learn and master regarding disassembly of this generation of Bang & Olufsen, the inner workings are easy to access.

The last boards removed are the first boards put back in.

I am not doing a full reassembly yet because I still have work to do on the displays. It is nice removing the transformer when moving the Beocord around and positioning it because it makes the unit a lot lighter. Here I have the Beocord reassembled to the point I can test it with a tape.

Now to the other side to see what happens when I push play.

Oh what a great feeling it is to see the unit come to life and actually play a cassette after all of that work! I verified music was coming out using headphones on the front panel jack. You can see that this display does have missing segments and I will be working on those soon. Tomorrow I will set up and run some tests on this deck to see what it looks like on the spectrum analyzer. I will also see if it records. It's nice to end the day with a good success.

Beocord 9000: Replacing Capacitors Wrapped Up

It took a little longer than expected but I am done with the capacitor replacement in this Beocord 9000 cassette deck. As expected most of the capacitors did test within spec. However, a few were out of spec and two were completely bad. On the Microcomputer/Display board there was that 220uF capacitor (C56) that was preventing the Beocord from coming on. Later, on the Dolby board I found another 220uF (C7) of the same brand that was also completely failed. So even though it is quite a big job it is worth checking out all of the electrolytic capacitors.

Here is a picture of the recap work on the Calibration Oscillator Detector board. Just three 1uF capacitors and I replaced them with WIMA MKS type capacitors.

Next is the Microcomputer & Display board. There are not many capacitors here and I will be returning to this board to work on the displays.

Finally, the board with the most capacitors, the Dolby board.

I will clean the slider and Dolby switches with Deoxit while I have this board removed.

Before starting work on the displays I need to check if the Beocord is functioning after the re-capping and re-soldering job. If not, I will have some trouble-shooting to do. So the next step is the re-assembly of the Beocord where I can test it again.

Beocord 9000: Replacing Capacitors

 Now that it is 2017 and the parties are over it is time to get back to the Beocord 9000 restoration. I started the work replacing the electrolytic capacitors. As I mentioned before, on these Beocord 9000 units it is often the case where very little if any recapping is necessary. This unit appears to have been in storage for quite a while and I already found one bad capacitor so I decided to replace the others.

I typically replace capacitors using audio grade capacitors in the signal path and high reliability, 105°C rated, long lasting capacitors everywhere else. In cases where the capacitor is not in the signal path and is 1uF to 4.7uF, I will often replace the electrolyic capacitor with a WIMA polyester capacitor (MKS). For this recap I removed the Beocord circuit boards so I could inspect and clean them better. I want to examine all of the board connectors closely and reflow the solder joints on them.
The first board is the power supply board.

The next board was the rectifier board.

After that as the Analog/Digital Converter board

Followed by the Record/Playback board.

There were three 10uF electrolytic capacitors on the Record/Playback board that I decided to keep. They measured exactly 10uF and had a lower ESR than new replacements that I had in stock.

Since I am also cleaning the Beocord up as I go I removed the Mic. Amplifier board so I could clean the switch and the plugs while I recapped the small board.

On most of these Beocord units I find a green, sticky substance on the shield wire of audio cables at the connectors. This picture is of a cable with that problem connected to the Mic Amplifier board. I cleaned off the goop and re-soldered the shield wire.

Here is the Mic Amplifier board all cleaned up and ready for re-installation.

I should have the remaining Beocord boards recapped tomorrow.