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Beolover SyncDrive: DC Platter Motor Replacement for Beogram 4002 and 4004 (Type 551x and 552x)

Late Beogram 4002 and the 4004 (Types 551x and 552x), which have DC platter motors instead of the earlier synchronous AC motors usually suff...

Thursday, August 22, 2019

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!

Tuesday, August 6, 2019

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.