Beogram 8000: Reassembly and Record Play

The time has finally arrived to put this Beogram back together and start having some fun playing records.

I didn't show it earlier but I sanded the small rust spots I found on the bottom section of the Beogram cabinet and spray painted some flat black paint over it. That should prevent any spreading of rust.

The first step of reassembly is to put the floating chassis and its components back in the cabinet base. That is followed by adding the circuit board, transformer and control panel.

Now the deck lid can be lowered and the floating chassis suspended from the leaf springs.
The top platter is put in place and this is starting to look like a Beogram again.

The tonearm compartment deck is left off for a bit so I can get to that leaf spring. Several iterations of removing the top platter and adjusting the suspension leaf springs finally get the platter surface even with the Beogram deck.

The dust cover and tonearm compartment lids are attached, the tonearm compartment deck and the long, black trim panel over the dust cover hinge. This Beogram is ready to play records.

Now for the fun part. I installed the Beogram 8000 in my office system where it will be living for a while as I do the hard work of laying back and listening to records. I decided to start off with a Lonnie Liston Smith album I bought back in 1977.

Beogram 8000: Finishing Up Some Odds and Ends

I am ready to put this Beogram 8000 back together and start playing records in my office but there are a few odds and ends to take care of first.

The muting relay is a component that has acted up on the last few Beogram 8000 projects. Because of that I now always replace it. The original muting relay on the Beogram 8000 is a National type relay.

Beolover makes an adapter board for several of the old relays Bang & Olufsen uses in their turntables. National is one of them.

This Beolover adapter board was originally created for the Beogram 400x turntables. I am able to use the board here and mount an Omron 12 VDC relay replacement for the National.  Due to the polarity of the Omron relay and the Beogram 8000 relay board layout I have to mount the board upside down.

Another quick task to do is to close up the microcomputer PCB box. I have left it open up to now in case there was some problem (i.e. the failed display segment I had to fix earlier).

I applied fresh thermal compound to the heatsink bar and reattached the lid to the shielding box.

From the end of the box where the microcomputer IC is you can peak inside and check that the heatsink and thermal compound made good contact with the device.

Last is to repair the tonearm compartment lid so the damping lever slowing closes. Like a lot of these turntables the original damping grease has been removed. It likely deteriorated over time. This unit has some sort of grease as a substitute but that really doesn't provide the correct damping.

I use Nyogel 767A. It is specifically designed for damping applications and it has worked great on these Bang & Olufsen components that have lids/doors that are dampened.

The damping on the Beogram 8000 tonearm compartment lid is performed by a plastic lever that is mounted on a pivot. The lid assembly presses on to this lever. The damping grease slows down the movement of the lever.

Here is the damping mechanism re-installed and ready for the lid assembly.

Now I can finally put all of the Beogram components back together.

Beogram 8000: Cosmetic Repairs

I left off in the last post for this project with the Beogram wood trim removed and soaking in GooGone to loosen the old mounting glue. The rosewood trim on the Beogram had started to separate in places and the only way to really fix it is to completely remove the trim, clean off the old glue, then reattach the trim.

Here are the pictures again of the removed trim soaking in GooGone.

After about an hour I can use a scraper to remove the old glue residue.

The old glue comes off pretty easy but the front trim piece was a lot more delicate than the sides. There were already places where the trim was starting to come apart. I repeated the GooGone process on the Beogram frame that the trim attaches to. Before re-attaching the trim I cleaned all of the mounting surfaces with acetone.

To remount the trim I used Tesa 4965 double-sided tape. It is very strong and worked really good on the front trim piece to keep the separating trim intact during the remounting.

Here is the front trim piece already mounted and the two side pieces prepared.

Here are the left and right corners after all of the pieces have been remounted.

The next step was to do some sanding and refinishing to bring the color back to the trim.

Here are some before and after pictures of three trouble areas on the front trim.

At certain angles you can see some scars but I think the trim looks good. I might give the front trim piece one more round of treatment but I want to put everything back together and get a complete look at it first.

Beogram 8000: First Record Play

Today I finished up the remaining Beogram adjustments so I could try out the turntable playing a vinyl record.

My Beolover custom part for the Beogram transformer box arrived last week. This replaces the non-polar, coupling capacitor for the linear motor coils that B&O put in the transformer box.

A very nice design on the replacement don't you think?

On the mechanical side the service manual says the distance from the top of the fixed arm to the platter surface should be 23 mm. I checked this Beogram and the measurement looks good.

There isn't any adjustment screw for that check. If the distance isn't correct then one would need to work with the plastic disc inside the bearing for the platter hub.  Beolover ran into a problem with that disc on a past Beogram project.

This Beogram platter and detector arm/tonearm height check out fine.

Next is a quick check of the tonearm tracking force calibration. I set the Beogram turntables where the 1 gram tracking force setting is calibrated to be 1 gram (as close as possible). With the tracking force scale set to 1 gram I adjust the tonearm counter weight so I get 1 gram on the scale.

The final adjustment is the tangential record tracking of the Beogram. Like the 400x series of turntables the 800x series uses a lamp and a light sensor at the base of the tonearm. An aperture that is part of the pivoting tonearm base allows light to reach the sensor. The circuit is adjusted per the service manual where the the tangential drive motor starts moving the tonearm after 2 rotations of a record. After that it moves the arm on every rotation. The sensitivity of the photo control circuit is adjusted using a small screw at the base of the lamp/sensor housing.

Once I had this adjustment set I let the Beogram play an entire side of a test record to observe that it completed play successfully. After that I tested that the Beogram 8000 could pause play, return to rest and resume play where the Pause button was pressed. All turntable functions checked out.

Here are some pictures of the Beogram playing a vinyl record.

These Beogram components are ready to be re-installed in the Beogram cabinet so I can start using the turntable.

Before I do that though, I have to re-attach the wood veneer that has started to come off the cabinet.
I will have to soak some GooGone where the original glue was and get the surfaces nice and smooth before re-attaching the veneer pieces.

Now it is just wait and let the GooGone do its thing.

Beogram 8000: Sensor Checks and Adjustments

The problem with the Beogram 8000 detector arm not detecting an empty platter turned out to be a simple adjustment to the sensor source lamp positioning.

The Beogram 8000 schematic shows the detector arm circuit and what the expected sensor signal should look like.

Measuring at C19 I could see the signal was not as strong as it needed to be.

I used a flashlight to apply more light and saw that the sensor output increased up to a working level.

The easiest thing to adjust and check at this point is the sensor source lamp position. I opened the lamp and sensor housing to move the lamp down a little inside the housing.

That did the trick. The detector arm now functions normally with the correct output voltage on the detector circuit.

While I had my Beogram test setup in place and my scope warmed up I checked the tangential arm position sensors. Here is the circuit diagram.

Both sensor outputs look good and the Beogram has been working as it should with regard to the tangential arm movement.

Another sensor output to check is the platter speed. This Beogram still has the original, plastic printed tacho disk. Let's see how it measures. Here is the circuit and measurement point.

Here is the sensor output for 33⅓ RPM and 45 RPM.

Last are the forward/reverse scanning LDR sensors. This is the adjustment I always add my custom connector for so I can check the LDR voltages at any time without having to completely open up the Beogram again.

Here is the circuit.

Here is a photo of the test connector I always add for the this LDR adjustment. This photo is from an earlier Beogram 8000 restoration project. It is the same on this current project. The wire colors used on the test connector were chosen to match the Beogram ribbon cable for those signals.

Here are the forward and reverse LDR measurements after adjusting them to be between 0.6 VDC and 0.7 VDC.

I believe this Beogram is working correctly electronically. Now I need to check the tonearm balance and the distance to platter surface. After that I will check the cartridge tracking and, if necessary, adjust the linear tracking sensor. I should be playing records on this Beogram real soon.