Beogram 4004 (5526): Restoration of the Arm Lowering and Tracking Mechanisms

As usual I started the restoration of the Beogram 4004 (5526) that is currently on my bench with rebuilding the arm lowering and tracking mechanisms. This shows the solenoid and damper section of the turntable:

I removed the damper and the linkages for cleaning and re-lubrication:

After I put everything back together it was time to do the same for the linkage that connects the damper with the tone arm. This shows the backside of the arm assembly:

The sensor arm can be taken out by removing two screws that hold it to the floating chassis of the Beogram:

Once the arm is out, the linkage can be removed:

Care needs to be taken to not loose the small spring that sits under the retaining ring. After cleaning and lubricating the pivot point I replaced the sensor arm assembly and adjusted the the arms to be parallel and orthogonal to the carriage guiding rods.

The next step was to replace the incandescent light bulb that provides the illumination for the tracking sensor with an LED assembly. LEDs last much longer than light bulbs and this increases the long term stability of the restoration. This shows the original bulb housing in place:

I removed it, which exposed the tracking sensor aperture:

This shows the original bulb housing in comparison with my LED replacement assembly:

The LED is in the same spot as the filament of the bulb. Like all Beolover parts this part is available to other B&O enthusiasts. Just send me an email or use the contact form to the right.

I installed the LED assembly:

The final item to address was replacing the cracking-prone plastic carriage pulley with a machined aluminum part. This shows the original pulley in place:

And with the replacement and a new belt:

Beolovely! On to rebuilding the electronics!

Beogram 4002: Working the Main Board

On this project I am starting with the electrical restorations. The main circuit board is first. As usual I will replace electrolytic and tantalum capacitors that are 2.2uF and less with WIMA MKS capacitors. If there is room I sometimes replace 4.7uF capacitors as well. In this case the fit is too tight to install 4.7uF WIMA capacitors so I will stick with electrolytic replacements on those.

Here is the main board again as I received it.

Here is the speed select relay removed along with the speed trimmer resistors.

I am replacing the 45 RPM and 33 RPM speed control trim pots with sealed, multi-turn trimmers. For the speed selection relay I am using Beolover's custom RPM relay component. It is a sealed SMD relay mounted on a special adapter board so it is a direct replacement for the original relay (A Siemens relay in this case).

A key component on this board is the 1C10 capacitor. Beolover's exhaustive testing of the rebuilt DC platter motors has determined that the value of the 1C10 capacitor has a measurable bearing on the stability of the platter motor speed. In his testing of the DC platter motor from this Beogram unit he determined that a 10uF capacitor provides the most stable speed circuit. 

Here is the completed main board with its new parts.

Beogram 4002: New Project From Houston

I get to switch gears from Beomaster restorations back to a Beogram project next. I love working on both so either way it is a treat for me. A gentleman from Houston brought me a couple of Beogram 4002 Type 5513 turntables he had acquired some years ago. Eventually they began to age and stop functioning correctly.  Like most Beogram 4002 owners he found that he missed playing vinyl records on them so he had to get them restored.  I am lucky enough to receive the task and look forward to getting these back 100% working again.

One at a time though.

These were functioning well for the owner not too long ago so the Beograms are in decent shape. Here is the first Beogram turntable opened up.

I already removed the DC platter motors back in March and sent them to Beolover for a full restoration. I have those motors back and they have been waiting for the rest of the Beogram restoration to catch up.

There are a few areas inside this Beogram where rust is starting to look bad. I will clean those up and put a stop to the rust. 

The Beogram phono DIN plug is badly corroded as well and the best solution there is to replace it.

Here are a couple of pictures of some of the chassis components that have rust.

Interestingly this Beogram 4002 is one of the rare few I have seen where the plastic transport bushings around the floating suspension locking screw are still intact. They are still soft and in good shape. Most of the units I see have brittle bushings that have cracked and are in a million little pieces scattered throughout the Beogram. I will treat the bushings with some plastic restoration fluid that will keep them from drying out.

The main circuit board looks in great shape. No signs of heat stress or corrosion there.

The tangential arm assembly also looks to be in good condition. 

Recapping the main board, replacing relays and speed trimmers along with cleaning and adjusting the tonearm mechanics should get this turntable back to working the way it was designed. The restored platter motor along with the replacement of the trimmers and speed indicator lamps (with Beolover's LED replacement modules) will have this Beogram spinning vinyl better than ever.

Time to get to work.

Beomaster 8000: Reassembly for Testing

I can finally start putting this Beomaster back together where it can be put through some functional tests. There is a final component that needs attending to however and that is the door damper for the lid that covers the Filter & Tone Control panel.

The Beomaster 6000, 8000 and Beocord units from this period share a door damper component that keeps a spring loaded lid from flying open. The damper applies some resistance to the spring so the door opening is more controlled.

Here is the damper that came out of this Beomaster 8000 unit. You can see that damping grease has started to leak out. I have seen units where the damping devices are still sealed and don't leak but I have also seen a bunch that are leaking. My guess that the environment they were stored in plays a part in how they have survived.

Here is the damping component opened up.

Ready for the new damping grease.

Here is the reassembled damper installed back in its place in the Beomaster.

It is easiest to reattach the door to the damping component with the Filter & Tone Control board removed. Now that the door is working again I can continue with the rest of the Beomaster reassembly.

During this phase of the project I test play the Beomaster every chance I get. The more actual use of the restored receiver the better. I noticed that the FM tuner didn't sound right and looking at the Signal-Multipath meter in the photo above there should be an illuminated red "MPX" lit up. It is dark in the photo. When the Beomaster 8000 is tuned to an FM stereo station the MPX lamp lights up to indicate it is decoding stereo FM. That is what my ears were trying to tell me. The FM tuner was tuning stations but they were only playing mono.

That means lifting the Filter & Tone Control panel to do a little trouble-shooting of the FM board. Since the problem seemed to involve just the FM stereo functionality I concentrated on the things that just relate to that.

I made some minor adjustments to the 1R45 (Stereo Decoder - oscillator) and 1R41 (Opening of Stereo Decoder) trimmer resistors. Doing that got the MPX LEDs in the Signal-Multipath meter to illuminate on an FM stereo channel. Unfortunately I was still only hearing mono from the Beomaster.

That left the Stereo Decoder chip (1IC3) as the next suspect. It is responsible for decoding the stereo signal.  Fortunately I had a spare TCA 4500A chip in stock.

That did the trick. The FM stereo channels now decode properly and the tuner sounds good again.
Here is the fixed FM tuner. The red arrow points out the illuminating MPX light.

Now to finish closing this unit up and begin the final testing.

Beomaster 8000: Display Board Back In Business

No problems with the Beomaster 8000 segmented display module burn-in test.  All that is needed to complete the display board is to reinstall the display modules and replace the four indicator lamps with Beolover LED replacement boards. The incandescent indicator lamps are for Clipping, Filters, Mono and Manual (as in manual tuning).

The four lamps are outlined in green dotted lines in the following picture. The blue dotted lines show four related resistors (R34, R36, R38 and R40) that are removed when the Beolover LED lamp boards are installed.

Like all of the Beolover replacement parts these lamp modules are direct plug in replacements for the original part. In this case there are the four resistors that get removed but if anyone in the future wanted to return to using incandescent lamps it is a simple matter of soldering in the resistors along with the lamps.

The display board works beautifully again. I tried out all of the modes and all LEDs illuminate as they are supposed to.

This Beomaster is ready to be closed back up and put through some final testing.

Beogram 4004 (5526): A New Arrival - First Look

A Beogram 4004 recently arrived for some TLC. It came without a sub-platter and also lacked the arm cover:

The platter showed damages from a cleaning attempt that removed the coating that creates that signature matte look of the B&O brushed aluminum surfaces:

Not much one can do about this except finding a new platter from a donor. Another damaged area is the front left corner of the plinth:

I also found some fragments pointing to degraded transport lock bushings:

A look at the output cable revealed a RCA conversion that needs to be optimized (I recommend to restore the original DIN7 output and use a RCA adapter if RCA is needed to connect to a non-B&O amplifier):

On the positive side, the keypad is in pretty good condition:

I removed the packaging and had a look under the hood:

It seems it is all-original, except that the two screws are missing that hold the tonearm to the carriage:

I also found the plexiglass needle protector from a MMC cartridge lodged in one of the cavities next to the hood screw holes:

I plugged it in, and it showed life signs: After pressing the START key the carriage started moving and it set down at the LP position, which is a good sign. The platter motor made the usual noises indicating dry brass bearings.

In summary, it appears this Beogram 4004 can be restored to its original functionality and beauty if a few parts are procured from a donor unit.