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.

Beomaster 8000: Ready for Some Bench Testing

Ever since I restored the power supplies, output amplifiers and preamplifiers on this Beomaster I have been exercising it with an iPod through TP1 & TP2 as well as playing the FM radio. The receiver has continued to play and sound very good as I added the restored FM boards, Filter & Tone Control board and the Microcomputer board. Now it is time to start putting the Beomaster back together and do some bench testing.

As I started the reassembly I tried the remote control for the first time. No functionality. So I will have to dive back in to the power supply board where the remote control receiver lives to see what is wrong. But first I decided to continue with some initial bench testing. I have been anxious to take some measurements and I don't see any reason to let the remote control problems delay that right now.

Before using any test equipment I decided to run a functional check pairing the Beocord 9000 that I restored earlier. These two will be returning together to their owner soon and I wanted to see how they play together for the first time since their restoration.

I used an original seven pin DIN cable for TP1 to connect it to the Beomaster. Pressing the play button on the Beocord turns puts the Beomaster into TP1 play mode as expected. Pressing the standby (off) button on the Beomaster turns both units off (and into standby mode). So they are communicating well. The Beocord also sounds great. In a later bench test I will add one of my Beogram 8002 turntables to the mix so I can both check out the phono input and do some recording on the Beocord.

Next up for this testing session though is to use my QA400 spectrum analyzer to check the Beomaster 8000 from its source input (TP1) to its output amplifiers (Speaker 1).

Beolover has featured some measurements before from his QA400. It is a nice little bench analyzer that uses a PC to do all of its analysis. The connection to the computer is via a USB cable and software on the PC sets up the tests performed. Up until now I have only done low voltage level testing with this type of setup because the inputs to sound card devices and this QA400 are limited to the ±5 volt range. Connecting to the power amplifier outputs was not doable. I picked up some differential voltage probes by the QA400 manufacturer that will allow me to measure higher voltages. For this Beomaster source-to-speaker test I will use a couple of fixed 8 ohm loads to simulate speakers and connect the differential probes to the dummy speaker connectors.

The probe is powered by batteries and has a BNC connector to run a coax cable to the QA400 input terminal. For some reason I could not get my test setup working as I wanted with both differential probes connected at the same time (one for the right channel and one for the left channel). With both probes connected I see some undesirable noise at 60 Hz from my house line voltage. So far swapping cables and probes doesn't solve the problem. The only thing that works is using one of the probes on one channel at a time. Then there isn't any 60 Hz noise present. So I performed my tests one channel at a time switching the speaker connection to the Beomaster. The measurement results look pretty good. I won't post all of the frequencies I checked (400Hz, 1kHz, 5kHz, 10kHz, 15kHz) but here is the 1kHz test on the left channel. I tested with the analyzer set to unweighted and A-weighted.

Here is a 5kHz test on the right channel.

Viewing the distortion numbers and sound to noise level readings at a few select frequencies was nice to see. This Beomaster sounds really good but I like to see some sort of measurable result besides my own ears.

Now it is back inside to see what is wrong with the remote control receiver.

Beomaster 8000: Tackling the Lid Damper

On these last two Beomaster 8000 and Beocord 9000 projects the owner had to have the damper devices for the lids removed as they had begun to leak fluid. This appears to be a common problem with the grease used by B&O on these series of components (Beomaster 8000, Beomaster 6000, Beocords 8000-9000).  Of course these these devices are thirty plus years old now so that has to be taken into account.

The Beocord 9000 I worked on doesn't have its damper anymore so I will replace it with a spare from another Beocord. The Beomaster 8000 damper is still intact although removed from the unit.

Here is a picture of the dampers I have available for this project and some of my future projects. The damper in the center has the most leakage of the bunch. Also shown are an original lid lever for the Beomaster 8000 and a 3D replacement lever that Beolover can provide. While the damper devices are the same between the various Beosystem components of this series, the levers are not. The Beomaster 6000 and Beocords require a different size lever. In the picture below the lever out of this Beomaster 8000 is not original. It is a pretty good hand-made replacement carved out of plastic. However, the plastic has become quite brittle and starts to break with the slightest pressure applied. The other lever is the Beolover 3D printed replacement. That is what I will use on this Beomaster.

This next picture shows a few of these dampers opened up. The two on the far right still functioned to some extent. The others no longer did much as their grease is pretty much gone. Two of the dampers had their plastic mounting clips melted in place as an attempt to keep the device sealed. I had to cut them open and they were pretty empty so the grease leaked out anyway. When I rebuild these my plan is to use black hot glue. I think it will hold secure enough yet allow disassembly in the future.

The next to last damper device on the right is the only one that had an additional, thin, white washer installed. I don't know if that is original or something that was added later by someone.

Here is a closer up picture of the dampers that still had functioning grease. Next to them is the replacement damping grease I will use. The thing to figure out next is how much grease is required for these dampers to operate correctly. Should the entire housing be filled? I hope not. One tube of this special damping grease is about $50 USD so it is quite an expensive product. However, it is made for the purpose of damping and claims it will not break down under high temperature.

Here is a cleaned out damper with the Nyogel applied. It is ready to be sealed up.

Beomaster 8000: Display Board Rebuilt

The reworked Beomaster 8000 display modules have spent enough time on the test jig. All of the new SMD LEDs passed the burn-in test so I can finish up the last circuit board in this restoration project...the display board.

Here is the board with its original components. The arrows designate the board components that will be replaced: The four display modules, the four light bulbs, a 10uF electrolytic capacitor and a 4.7uF tantalum capacitor. The four light bulbs will be replaced with Beolover's direct replacement LED component. That means also removing four 220Ω resistors (R34, R36, R38 and R40). As with all of the other Beomaster 8000 board restoration, I reflow the solder on all of the board connectors.

Here are the lamps and resistors alongside the new Beolover indicator light modules.

Here we go, the last board re-installed in the Beomaster...and everything works. An expected result but always a relief to actually see.

Note that it is always difficult to get a good photograph of the LED displays the way they really look. If I turn down the ISO and shutter speed I can get a better representation of the displays but then everything else is too dark. The display segments all look uniform and will match the Beocord 9000 I did earlier.

This Beomaster is about ready to close back up for the bench, system testing phase. However, I do need to rebuild the lid damper before I can put this unit back together so it is time to start that repair.

Update: Here are some better photos of the new displays in the Beomaster. They look quite good I think. I followed Beolover's basic restoration method of blacking out any sources of stray light from the LED using various materials like black vinyl tape and black hot glue.

Beomaster 8000: Microcomputer Board Reworked

Today was the day to work on the Beomaster 8000 microcomputer board. On an earlier post I noted that this Beomaster is an earlier model unit so it has the first generation Beomaster 8000 microcomputer board. The later model boards are direct replaceable but are definitely different. I will show an example of the late model microcomputer board at the end of this post.

One thing I don't like about these first generation boards is the metal enclosure around the processor ICs. It is necessary for shielding of course but these early boards are difficult to open up. B&O soldered metal tabs to connect the upper and lower sections of the metal shielding box. The problem is the tabs also solder to the ground plane of the the microcomputer board. Because tabs are soldered to the ground plane a lot of heat is required to melt the solder for removal. When people try to open the shield box up to get to the components they usually damage the traces on the board where the shield box mounts to it. This Beomaster has been serviced before and falls into the category of having damage to the mounting points.

The following picture shows the two different Beomaster 8000 microcomputer boards. The board for this project is the bottom board. Notice that the metal shield box on the top board is pressed to fit while the bottom board is soldered together (red circles show some of the solder locations).

Here is the microcomputer board for this project as it was before restoration.

Here are the covers removed.

The early model boards used a metal bar for a heatsink on the two main processor ICs (IC3 & IC4).
The places circled in red show the damaged places on the board where the mounting tabs for the case originally were. The last person to work on this unit was able to re-seal the box with solder but I won't want to do it that way again as I don't trust the grounding with those missing tabs.

This is similar to what B&O used in the metal shield box for the Beogram 8000 and 8002 turntable processors. A strip of special tape is used to keep the messy thermal paste off the ICs themselves.
Here is the component side of the board with the thermal tape removed. The restoration task will be to replace the 22uF electrolytic capacitor to a 105°C, high reliability type. Also the 1uF tantalum. Following Beolover's lead I will also replace the two oscillators for the processor ICs (X1 & X2). Those will require changing two capacitors on each to new ones that match the new oscillators (18pF). Last, I will also reflow the solder joints on all of the connects and board vias as those have been known to have hidden problems.

For the oscillator capacitors, this original board has two 12pF capacitors for each oscillator. One oscillator has its two 12pF capacitors on the component side. The other oscillator has them on the trace side. 

The later model microcomputer boards have mounting holes for the oscillator capacitors on the component side.

Here is the microcomputer board with its updated components.

CAUTION: As Beolover noted in his Beomaster 8000 restoration, messing with the crystal oscillators could be a risk to the two processor ICs (IC3 & IC4). As a safety measure I shorted the two oscillator leads together and removed the processor ICs from their sockets (using an ESD grounding strap of course). With IC3 and IC4 safely out of the way I performed all of the rework to the board.

After doing the tedious solder reflow work it is time to put this board back together. I re-inserted IC3 and IC4, then prepared the heatsink thermal tape and compound so I could remount the top and bottom covers.

Now to solve the broken ground points where the metal covers mount. I have solved this problem before by using copper tape the way metal bands are wrapped around crates for shipping. The copper bands fit perfectly in the board slots where the mounting tabs go. I solder the bands together on the top and bottom of the metal box. I also solder the copper bands to the metal box so the grounding will work as it is supposed to. To tie the box to the board ground planes I run a copper tape strap to the main ground lug (both on the top and bottom side of the board).

The result is not the prettiest thing (rather ugly really) but it is solid and works. The copper straps securely keep the box together and I can measure good ground continuity anywhere on the board. If I have to do this type of repair again I think I will apply strips of copper to the lid pieces first (to use as solder pad anchors if you will), then tie the bands in with those anchors.

Removing the assembly should be pretty easy.  I didn't solder the copper straps on the sides where the top and bottom pieces meet. To open this box up again I only have cut the straps along the sides, de-solder the two main ground straps and the box will open up. In the picture below I marked the cut points with the red arrows. Note the green arrows. Those show the previous repair where someone fixed the broken ground connection by scraping away some board coating at the ground plane and soldered that right to the metal housing. While that should work I think it is risky because it is susceptible to the solder joint cracking if the metal box is stressed. I like the straps better because they provide a much more reliable connection to the ground plane of the board. The grounding strap also has a little give in it so it can withstand any movement.

Now it is time to test this updated board in the Beomaster 8000. 

I am happy to say that works great. Now it needs exercising for a while to make sure there aren't any hidden problems.

For reference - Here is a Beomaster 8000 later model microcomputer board I restored earlier.

These cover plates are easy to remove as they just press-to-fit. Not the rectangular tabs in the top cover plate. Those make contact with the two main processor ICs (IC3 & IC4) to transfer heat away from the ICs and to the metal shield box for disapation.

Here is the component side (restored). Both sets of 18pF capacitors for the new crystal oscillators are on the component side of this board.  Also notice that this board has a frame for the top and bottom covers permanently mounted to the board. This frame provides all of the structure. There is no strain on the board layers and no soldering of the shield box. Way nicer for servicing.

Here is the trace side of the board. All I did on this side was reflow solder joints.

Now I need to get back to the assembly of those Beomaster 8000 display modules so I can complete the last board.

Beomaster 8000: Updating the Displays - Preparation

The next task on the list is updating the Beomaster 8000 displays. For the big, segment displays that means replacing the original Beomaster LEDs with modern, surface mount type LEDs. It would be great to be able to leave the original LEDs  (and sometimes an owner will do that), but eventually those LEDs fail. These units are thirty-five years old now. It is expensive to ship a Beomaster 8000 due to its size and weight plus it is a good idea to keep shipments (as in re-shipment) to a minimum. Lessen the chance of something bad happening in transit.

Here are the segment displays from some Beomaster 8000 units.

The first step is to get a test rig set up for these Beomaster displays. The work will be just like I did earlier on the Beocord 9000 display (...just more LEDs). You can setup a jig without load resistors and use the current limiting of the bench power supply but I want to set up my jig with individual control lines and load resistors like the Beomaster. I came close on this initial test set up but ran short of 68Ω and 82Ω resistors. I will have to add them to my next Mouser order which will probably be this week. Anyway, though not completely like I wanted, this test rig will allow me to check the reworked display boards. This picture shows the rig with a set of Beomaster 8000 displays that have all working LEDs.

Here are the individual Beomaster 8000 display pin mappings.

Now I am off replacing the LEDs with new SMD LEDs. Once that is complete I will use the test jig to run the displays for a few hours so I will know they are good. Then they will be assembled and re-installed in the display board. While the LED burn-in test is running I will be able to do the recapping of the display board and the microcomputer board.

Beomaster 8000: FM & FM Interface Board Rework

The FM & FM Interface board assembly (the two boards connect together) appear to have been at the heart of the post burn-in failure that threw a circuit breaker in AC line powering the Beomaster. Once I had rechecked the power supply and output amplifier boards, I found that the Beomaster power up relays for the ±55 VDC rail voltages would fail to engage due to the Beomaster's fault protection circuitry. Unplugging power from the FM Interface board fixed the problem and I began using a spare FM/FM Interface set of boards for the Beomaster tuner.

My plan was to find the bad parts in the FM boards during the recap process and then re-install them. I discovered several defective transistors and a defective diode. This picture shows a couple of the damaged components on the FM Interface board. Since those components were bad I also replaced the three OpAmps on the FM Interface board.

After repairs were made to this board I re-installed it back into the Beomaster. Upon applying power and first selecting TP1 as the source input, I immediately started hearing a buzz in the speakers. Power was quickly removed as well as the FM board assembly. Something there is still not right. I am lucky nothing got damaged and installing it was not my best idea. This board needs to be wrung out on the bench by itself before testing it again in a Beomaster. 

To move forward with this project I decided to take one of my spare FM assemblies and use it. I selected the FM assembly that was closest in part number to the removed FM assembly.

Like the removed, faulty FM assembly I had replaced the electrolytic and tantalum capacitors plus the three TL072 OpAmps. One difference with this spare is that I used sockets for the OpAmps so I could experiment with different OpAmp types. The installed OpAmps here are OPA2134PA chips. The same kind I used in the Filter & Tone Control board.

To be consistent and to provide peace of mind, I decided to replace the TL072 OpAmps in the preamplifier board I completed earlier. Here is the preamplifier board with the OPA2134PA OpAmps installed.

This completes all but the Beomaster Display and Microcomputer boards. I will tackle the Display board next as it requires the most work in updating the displays modules with SMD LEDs.