Beogram 4004: Restoration of DC Platter Motor

I recently received a Beogram 4004 DC platter motor from Texas. The motor exhibited the typical shrieking noises when running it from a bench supply at 5V. A clear indication of dry bearings.

This shows the motor as received:

I took the motor apart to get the brass bearings out for oil infusion:

The bearings are the two small donuts on the black pad up front. I immersed them in motor oil and pulled a vacuum. Immediately vigorous bubbling started, indicating thirsty bearings:

After about 48 hours the bubbling stopped (indicating that the bearings were replenished with oil) and I extracted the bearings:

Then I reassembled the motor and installed it in one of my Beogram 4002s for a 24 hrs RPM stability test using the BeoloverRPM device. The BeoloverRPM allows logging the RPM every 10 seconds over extended periods of time. This is the curve I measured:

This result is as good as it gets! This motor is ready for duty again!

Beomaster 8000 - How to open into service position

For the DIY Beomaster 8000 owners out there here are some visual instructions on how to open up a Beomaster 8000 into its service position. This is useful when an owner wants to inspect and measure some internal component or if a board needs removing for replacement.

First...here are some instructional diagrams to open the Beomaster 8000 from the service manual.

NOTE: Do this with the Beomaster 8000 power cord unplugged.

Here are corresponding photos of what those actually look like.

NOTE: Many Beomaster 8000 units do not have the complete set of the three flat, metal springs.

             Those springs just lay in place so often fall out when someone carelessly opens up the

              Beomaster. As a result the springs get lost. Always have a small plastic box or bag to 

              put the removed parts.

After the springs are carefully removed and stored there are some retaining screws that secure the front panel of the Beomaster to the chassis.

With the panel securing screws removed the front panel can slide forward and lifted up to its service position.  There are three brackets the were holding the front edge of the panel to the Beomaster chassis. Those brackets are now used to set the panel upright on the front edge of the frame.

Next is the smoked glass cover over the Beomaster 8000 displays. To remove that assembly there is a black plastic trim piece that must be removed.

Under the trim piece are three more screws. Those three screws only need to be loosened in order to slide and lift the glass panel out.

The Beomaster 8000 display board is not revealed. At the top of the display board are two securing screws. Those need to be removed to put the Display board and Microcomputer board into their service position.

NOTE: It is not uncommon for one or both display board tabs (B & F in the photo) to be broken 

             from mishandling.

The Display board is connected to the Microcomputer board which connects to the Beomaster 8000 chassis by a pivoting hinge. Together, via the hinge, both the Microcomputer board and the Display board can be tilted up into the service position. A slot in each hinge locks the assemblies in place.

Now the Beomaster 8000 Power Supply board and Right Channel Output Amplifier board are visible and accessible.

Next is the left side of the Beomaster 8000. There is one screw remaining where the release bar was removed. This screw is holding the Filter and Tone Control panel in place.

Once that screw is removed the Filter and Tone Control board and panel assembly can be tilted up into its service position.  Unfortunately Bang & Olufsen did not provide a built in mechanism to hold this assembly in the service position. I carefully place a small screw driver to hold the panel open.

At this point all of the Beomaster 8000 boards can be accessed. 

Full access and removal of the left and right Output Amplifier assemblies involves more disassembly steps from this point. Those steps will be added to the blog in the near future. This post focuses on opening up the Beomaster 8000 to its basic service manual position.

TIP: If you want to remove one or more of the now accessible boards from the open Beomaster, keep

        in mind there are quite a few cable connections involved in the removal process. It is always

        good to take plenty of pictures but I recommend using a black Sharpie type felt marker to label

        all of the connectors. Even though I have disassembled a lot of these amplifiers I still label the

        connectors to make reassembly easy.

Beomaster 2400 Type 2902: Problems found during performance testing

This Beomaster 2400 had breezed through the early burn-in tests and listening to it during that time sounded like any other restored Beomaster 1900/2400 amplifier. To really compare the performance however we like to take some THD (total harmonic distortion) tests and look at a frequency response plot.

The early THD tests showed nice values at close to 6 Watts of output into 8Ω dummy speaker loads.

As I continued measuring the performance while increasing power the output began to deteriorate to where I was getting out of spec THD prior to reaching the rated 20W power output. Actually, my Beomaster 2400 Type 2902 claims 25W continuous power into an 8Ω load. The Type 2901 service manual claims 20W continuous power into an 8Ω load.

I stopped and rechecked the no-load current settings.

Those values look good so I did another physical check.

I could see some cracks in the emitter resistors. Pulling them out and measuring them didn't reveal any problem with their value though but I changed them anyway. Because the Beomaster still plays decently this is a case where it would be helpful for a hard over failure.  As it is I will have to start replacing and retesting parts in this Beomaster output amplifier. Pulling out transistors and measuring them while they are not under load will likely not reveal a bad transistor.

This will take a bit of time and I already scheduled a week or two off so I will pick this amplifier back up later.

Beogram 4004 Type 5526: Second Beogram 4004 from Texas - Shipping to new owner

After this second, original owner, Beogram 4004 turntable restoration the owner decided to put it up for sale here on the Beolover Blog.

I am pleased to say that this beautiful Beogram 4004 now has a new owner.  This post shows how to prepare and pack the Beogram 4004 for shipping.

We have had quite a lot of experience now in packing and shipping various Bang & Olufsen components. Our methods have tweaked here and there. Turntables are the most critical to pack safely. Mechanical parts must be secured and of course the turntable itself must be protected.

As tempting as it is to secure the turntable for shipping without removing the phono cartridge it is still best to remove it.

The removal and installation of a Beogram MMC phono cartridge is not too difficult.  I always make sure the stylus guard is in place when handling the cartridge.

In this first picture of the cartridge removal process I show how I secure the tonearm with my fingers so it won't move when pulling the cartridge off.

With the other hand I grasp the phono cartridge and stylus guard to pull the cartridge from the tonearm connector. It will resist coming off as the fit should be tight. Do not wiggle the cartridge horizontally. It comes off straight and slightly down. Don't force it.

Here you can see the connection points of the MMC cartridge and tonearm connector.

The Beogram 400x turntables have a floating chassis for the platter and tonearm assembly.  There is a chassis lockdown procedure to secure the floating chassis for shipping (or even transporting to a friend's house :-) ).  In the case of the Beogram 4004 turntable there are three floating chassing lockdown screws. They are accessible from inside the cabinet and from outside the cabinet. The normal case for an owner is to use the outside lockdown screws.

The screws are on the underside of the Beogram 4004 cabinet and you DO NOT want to turn the turntable upside down to get to them.

I hang the edge I am tightening or loosening over the edge of a table and operate the screw from underneath.

This photo shows the three Beogarm 4004 lockdown screws as seen from underneath (hanging over my workbench table). The lockdown screws do not need but a couple of turns to loosen them. Gently turn the screw driver until it won't turn but do not apply a lot of torque. Don't over tighten the screws.

Now that the phono cartridge is safely removed and the chassis is locked down for transport the packing can begin.

My first step on this turntable packing was to put a protective plastic film (like you find on new products) over the outside of the Beogram dust cover. I didn't photograph that process but the film just lays over the dust cover.

After that I remove the Beogram top platter. It is another one of those things that is tempting to leave in place but it is better to removed it and pack it separately.  Why take any chances?

I cut and place a foam insert where the top platter was and a couple of strips of foam padding over the keypad and speed display.

Then I cut to fit, a piece of polyethylene foam to secure the remaining space between the dust cover and inside of the Beomaster.  I wrapped the polyethylene foam with the same plastic film I put on the outer surface of the dust cover.  Although the foam is pretty soft I worry that movement during shipping could result in swirl scratches on the underside of the dust cover. The film should prevent that.

Now I can close the dust cover and secure the main parts of the Beomaster.

I don't like to use any tape with adhesive if possible so I wrap the Beomaster dust cover down on the cabinet with packing wrap.  After that I like placing the audio component in a plastic bag to protect against any moisture. I also hate the way the electrical cord and phono cable can dangle and the plugs potentially scratch something.  So I wrap them in foam.

The next step is wrapping the Beogram lengthwise and crosswise with egg crate type soft foam. The foam is secured with plastic wrap.

This Beogram 4004 is now ready to go into the shipping box.

Over the last few years I have found that it is better to use as small a shipping box as possible. Too large of a box becomes difficult for shipping carriers to handle and increases the chance of a drop.

With the Beogram securely tightened down and padded the job of the box is for rigid support and protection from handling mishaps (bumps and small drops).

I use double-walled cardboard shipping boxes and glue the bottom flaps together.  After that I glue polyethylene foam sheets to the bottom and the four walls.

The wrapped Beogram 4004 fits right into the foam lined area.

This is where the Beogram 4004 top platter gets packed. I like to use a vinyl record shipping box to hold the platter.  I also add some small polyethylene pieces on the side of the Beogram and slide the box with the phono cartridge in there.

The final steps are to add the last polyethylene foam sheet for the lid and then secure the shipping box.

This turntable is now on its way to a new home.