Beogram 4000: Replacement of Corroded DIN5 Plug and Installation of a Grounding Switch

After rebuilding the control cluster the next step of my current Beogram 4000 restoration was to replace the original corroded DIN 5 plug with a modern gold plated all-metal plug, and to install a switch that allows connecting system and signal grounds in case there is a ground loop causing a hum in connection with the amplifier. This shows the rusty original plug:

And here the replacement:

Pretty! On to the grounding switch. This shows the terminals where the DIN cable is connected to the internal cartridge wiring:

This is the perfect spot to install the switch:

This switch allows to toggle between the B&O-original setup, where signal and system grounds are kept separate, and a configuration where both grounds are connected. B&O actually adopted this configuration in later 4002 and the 4004 Beograms. My experience is that if there is a hum, this connection in most cases suppresses it.

Beomaster 8000: Project Start - Initial Check

The Beomaster 8000 is now on the workbench and work begins with an initial check of what works and what doesn't. This Beomaster is in very good shape and when I connected up a couple of music sources (iPod Nano into TP2 and the BM8000 P1 FM station) I was a surprised the Beomaster played beautifully. I started to wonder if any work should be done on this receiver.

The happiness was short lived as the Beomaster stopped producing sound after ten minutes. Here is the Beomaster playing the local classical music FM station.

The first time the Beomaster stopped producing sound the display still showed 2.9 on the volume level, P1 as the tuner selection and 101.1 as the station. I put the Beomaster back into Standby mode then reselected P1. The music started playing again but after a few minutes, no sound. The second time the Beomaster display changed to tuner P and channel 87.5.

The Beomaster is definitely malfunctioning. It is time to open it up into service position and assess the work. Like the other Beosystem 8000 (and 6000) components from this early eighties period, Bang & Olufsen provided nice service access to work on these units.

Here is the Beomaster with the rear cover off, the front panel in service position and the display cover removed.

Here is the rear panel of the Beomaster.

When I unlatched the Beomaster locking bar for accessing the service position I noticed that one of the leaf springs that keeps the locking bar in place is missing. I will have to see if I have a spare in a parts unit.

This picture shows a better look at the Beomaster 8000 display board. The restoration plan is to convert the original LEDs with the SMD LEDs like those that were used in the Beocord 9000 display repair. So quite a bit of soldering is ahead.

Diving further into the insides of the Beomaster I discovered another missing piece. Like the Beocord 9000 unit, this Beomaster has a missing lid dampener. I am guessing this one was also leaking damping fluid. I also noticed that the Beomaster is missing the far left leaf spring for the locking bar. I will look for a spare dampener as well as the two missing leaf springs.

The previous picture was the left side of the Beomaster. Here is the right side (as viewed from the end looking in).

Most of the electrolytic capacitors look like they are original so that puts them in the mid-thirty year old range. The big black axial on the Power Supply PCB looks like it might be a replacement. This unit has been serviced in its past apparently.
Here is a better look at the left and right channel output amplifier boards.

It is time to take inventory of the capacitors and trimmers I need to replace in this Beomaster.

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.

Beogram 4000: Restoration of the Control Panel - LEDs and Gold Plating of Switch Terminals

After gold plating the carriage position switches, it was time to rebuild the control panel of the Beogram 4000 that I am restoring right now. I usually replace the incandescent light bulbs with LED assemblies, and I gold-plate the switch terminals to ensure trouble-free operation down the road.

This shows the original keypad switch terminals, which were quite oxidized:

I removed the terminals:

And gold coated them after removing the oxidation with a fiber glass pen:

And like with the last Beogram 4000 that I did, I forgot to remove one terminal in my first approach...not funny! Here we go:

and after coating:

Pretty, aren't they?? Then I soldered them back into the PCB:

The next step was to replace the light bulbs with LEDs. This shows them in action:

The position scale illumination bulbs were replaced with my custom designed dual red/green LED assemblies:

These boards are available to other enthusiasts. Just send me an email if you want to upgrade your Beogram 4000!

The bulbs that illuminate the RPM trimmers from the back were replaced with through hole high brightness LEDs that are dimmed with 3.3k resistors:

Using strongly dimmed high brightness LEDs saves more current further reducing the strain on the transformer of the Beogram (which gets pretty warm during play) along with the other LEDs that I implanted.

This is an impression of the LEDs in action:

The red-green LEDs create a very authentic background illumination for the position indicator while the presence of red photons in the LED light ensures that the indicator shows up red like when illuminated with incandescent bulbs.

Beogram 4000: Gold-Plating of the Carriage Position Switch Terminals

The next step of my Beogram 4000 restoration was to electroplate the carriage position switch terminals with gold. In my experience 90% of all operational trouble with this B&O design comes from oxidized switch terminals. These switches present the digital control system with the necessary inputs about the carriage status and if they malfunction, the control system gets thoroughly confused. So my recommendation is gold-plating of the switch terminals. Gold does not oxidize easily and therefore this will result in significant long-term reliability improvements. This shows the carriage switches as I found them:

Not too bad compared to what I found before in other Beogram 4000s, but definitely some black spots indicating oxidation. I removed the terminals:

The oxidized contact points are clearly visible. I cleaned and gold plated them:

And soldered them back into the circuit board:

the next step is to do the same for the switches in the keypad.

Beogram 4000: Restoration of the PCBs - New Capacitors, RPM Trimmers and RPM Relay

After replacing the motor and reservoir capacitors of the Beogram 4000 that I am restoring right now, it was time to rebuild the PCBs. I usually replace all the electrolytic capacitors, the RPM trimmers as well as the RPM relay. This shows the main PCB 'flipped' out (the 4000 PCBs cannot be removed easily since they are hard wired to the other components):

This shows the rebuilt board after replacing the components:

The new relay in detail:

They are available to other enthusiasts. Just send me an email or use the contact form on the right. It is a good idea to replace them, since the original Siemens relays are often oxidized preventing proper RPM switch-over. On to the RPM trimmers:

I use 25-turn trimmers, which make it very straight forward to adjust the RPM precisely and durably. 1VR1 (33 RPM) is 50k and 1VR2 (45 RPM) is 10k. This shows how the adjustment screws protrude through the PCB that one can adjust the RPM with the board bolted in.

There are two more capacitors on the smaller power supply PCB. This shows it in its original condition:

And after replacing the two red tantalum caps:

On to the remaining restoration tasks.

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.