Beomaster 8000: Repairing The LED Segmented Displays

The Beomaster 8000 has very distinctive, large, red LED segmented displays that are part of its modern design Bang & Olufsen created in the early eighties. The same type of displays were used in the Beomaster 8000, Beocord 800x & 9000 cassette decks as well as the Beomaster 6000 (225x).

Here is a Beomaster 8000 with restored displays.

Here is a Beomaster 8000 with original displays already starting to fail.

Now a picture of the display components removed and a view of the front and backs together.

After disassembly of the display modules here are the various pieces.

The next photos show the details of each display (balance, volume, source selection and FM frequency). The segment identifiers are shown as well as the display component connector information (+5V or Ground) to illuminate the LEDs.

As you can see the actual LED component is not a typical, discrete LED device from that era that was soldered onto a circuit board. These LED devices were manufactured special and attached to the board by some special process. An early form of surface mounted components?

Take a close look at the original LED device on the board.

Now look at the original LED device compared to its modern surface mount LED replacement.

The SMD replacement is like a nice packaged version of the original. A perfect replacement.

The mounting of the new SMD LED devices is critical. The construction of these B&O segmented displays is such that the LED must fit right in the small slots of the plastic light guides. The bottom of the light guide piece must press flat against the surface of the circuit board to block any light from illuminating adjacent segments.

This picture shows the display components better. The top left picture shows the slots the LED must fit completely inside of.

That precise positioning spoiled a plan I had to quickly install the replacement SMD LEDs using an SMD work station. I wanted to place the whole set of LED devices on the board in some SMD solder paste then use the work station hot air gun to perform the soldering all at once. As you can imagine some of the LED devices moved off line due to the air flow from the solder gun.

The tried and true technique is to solder each LED in place by hand using a two step process. After applying generous solder flux (I use no-clean flux) to the board solder pads followed by tinning the solder pads, I gently hold the LED down with a flat metal blade as I apply a dab of solder with my soldering iron (using a very small tip). I check the position of the LED with the light guide. If it is correctly in position I solder the other side of the LED and move on to the next one. Very tedious and labor intensive for sure but it works every time.

Here is a display board with the replacement LEDs soldered in place.

Now repeat that for the other displays. For the Beomaster 8000 that is sixty-five SMD LEDs to install.

There is also some preparation of the circuit boards before installing the SMD LEDs. Some of the original LED mounting pads are a little too close together for my liking to try and fit in the new LEDs.

Here are some photos from a Beocord 9000 display restoration I did that shows what I mean about the mounting pads.

Here are the pads after the original LED devices have been cut out.

The small tabs marked in red are the pieces I want to remove.

I use a razor blade to cut the original LED device from the board trace pads. I also use the razor to cut out the small trace tab shown by the red X above. You have to be very careful and steady while doing both steps. A slip of the razor and you have a broken trace to repair. Not a good scenario. However, with the removed tab the SMD LED fits much better. Perfect really.

Here is the Beomaster 8000 volume display board after the traces have been prepared (trimmed and tinned).

And here are the SMD LEDs soldered in place.

For reference, the SMD LEDs we use are Lumex SML LX06031W-TR devices.

After the display components have been retrofitted with the new SMD LED devices they need to be tested to make sure all of the LEDs illuminate. We use a home-made test jig to perform a 24 hour burn-in test of the displays before we go to all the trouble of sealing them up and re-installing them in the Beomaster.

I use a test jig where I have duplicated the Beomaster load resistors. I use a bench power supply for 5V power and ground.  Here are the displays being tested in various stages of assembly.

An optional step we do on our display restorations is to fully black-out the display component when we put everything back together. We found that by doing this we eliminate any stray light from the displays illuminating Beomaster areas that should be completely blacked out.

The sealing is necessary anyway as the original display components sealed together via a one-time-use plastic tab that was melted in place. To open the display for repair that plastic tab can only be cut off.

This display is now mechanically re-sealed and light beam sealed.

That is the whole process of restoring the display component.

Two other Bang & Olufsen audio components from this era share this LED segment display design. The Beomaster 6000 (225x) receiver and the Beocord 8000 - 8004, 9000 cassette decks.

At first look people (myself included) hoped that the displays are common and interchangeable. They are not. Here are some pictures of the displays from the various audio components side-by-side.

Even though the display segments for the display components above share the same look and number of LED segments, you can see that the mounting connectors are different and the control lines (on the rear trace side) of some of the boards are completely different. The only two that might actually be wired the same are the Beomaster 6000 and 8000 selected source display. But to try and swap those would mean a mechanical challenge of trying to get the connector leads attached properly.

The best thing to do if you have one of these components with faulty LED segments is to properly replace all of the display component LED devices with new SMD LED devices.

I hope this information is useful to other Bang & Olufsen Beomaster and Beocord owners out there.

Beomaster 8000 & Beocord 9000: Completing the Restoration

The final step in this Beomaster 8000 and Beocord 9000 project is a system test. To do that I needed plenty of space as these units take up a lot of room. Especially when you add in a Beogram turntable to complete the system. It is also time to clean up and put parts away. My soldering bench is my largest desk so I used it to set up the system test.

Here is a picture of everything layed out for testing.  Quite lengthy! With all of the system connected together the dependent functions can be exercised. A really nice feature of this system is that turning on one component will notify and turn on any related component. For example, placing a record on the Beogram and pressing the Beogram play button will turn on the Beomaster and switch it to phono mode. Same thing for the Beocord. Conversely, selecting PH (phono) on the Beomaster will cause the Beogram to operate. Turning the Beomaster off turns all of the other components off. To make things even nicer, all of these features also operate from the wireless remote control. The well thought out design is what makes this Bang & Olufsen system my favorite. Of course B&O continued some very cool integrated systems after this one but this system was a few years before the digital age and is analog audio at its best.

I continued testing by doing some recording on the Beocord 9000 with the Beogram 8002 as the source. I used a new TDK MA90 cassette (metal type IV) and ran the Beocord tape calibration procedure. This is when you start really appreciating the complexity of the Beocord 9000. After calibration I selected Tape End so the Beocord would run through the tape once and figure out exactly how much recording time is available on the tape. The Beocord tape counter of course displays the amount of time used and remaining. Really handy if you want to fill up as much music you can on a side.

For the recording test I like to use music with some distinct instruments and some that really get up there in range. That usually means some brass. So this time I selected an old Maynard Ferguson album from 1973, "M.F. Horn 3". It has that early 70's sound and of course Maynard screams on the trumpet. Quite fun if you like that era like I do. The recording testing all worked perfectly. I also tested pausing and restarting recording. The Beocord fast forward and reverse functions all work great (remember the belts and pulleys are all new). This is the payoff for the time and effort it took to get these beautiful machines fully restored.

With all of the Beosystem 8000 functionality working beautifully it is time for their owner to enjoy them so Beomaster 8000 and Beocord 9000 are ready to be packed up and shipped home.

For me it is time to prepare for the next project.

Beomaster 8000 & Beocord 9000: Re-Installing the Lid Dampers

In the last post on the Beomaster 8000 lid damper restoration I left off with the first damper cleaned out and fitted with new damping grease. I had to experiment with the re-assembly of the dampers to get them sealed and working properly. Out of the six damper assemblies I had available I have restored four so far. Here is a lid damper completely disassembled.

Here is another picture of the damper with new damping grease ready for joining the two main pieces.

Next is the joining of the damper and Beolover replacement arm to the deck lid. It should be done with all of the components removed from the Beomaster. Snap the new arm to the deck lid first. After that the other end of the arm attaches to the damper by sliding over the keyed mounting post on the lever. 

Now it is ready for re-installation in the Beomaster 8000.

The Beomaster 8000 deck lid now opens slowly and smoothly as controlled by the damper device. This is the result I was looking for.

Also part of this lid damper restoration is the damper for the Beocord 9000 that goes with this Beomaster. Again, installation of the reworked damper is done with the lid removed from the unit.

The Beocord still has its arm intact. Note that while the damper unit is identical to the Beomaster, the arm for the lid is not the same. The Beocord arm is shorter in length.

Here is the reworked damper installed back on the Beocord deck lid. Note the position of the damper lever and arm. As was the Beomaster, attaching the arm to the damper is done by sliding the arm on from the side. To install this on the Beocord deck lid the result will be the arm on the lower side of the damper. After the arm is attached to the damper you must rotate the damper 360° so the arm is on top (as shown in the picture below). Otherwise the damper won't be able to do its job.

Now the deck lid assembly is back in place and this Beocord 9000 has a properly working deck lid again.

This concludes the lid damper rework for these two units. The new damping grease should not liquify and leak like the old grease did. At least not for another thirty plus years.

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.