beolover: Beogram 4000: Resurrection - Full Functional and Cosmetic Restoration

A couple years ago I bought a Beogram 4000 from a gentleman in Germany. Sadly, the unit was not packaged properly (only single boxed with maybe 1 inch of padding - those frugal Germans!...;-) and it arrived in a sorry state. This post discusses the full restoration of this unit and upgrade with a Beolover switchable internal RIAA pre-amplifier.

This shows the unit after the restoration:

This unit is currently for sale at the Beolover store.

When I took it out of the box it looked a little less glorious:

It had received a blow on the left corner which caused the plinth to dislocate on the right corner,

which could have been fixed, but the main damage was of course on the left where the corner was completely mashed in. Also the hood cracked in that corner:

This meant both hood and plinth needed to be replaced. At least the platter was packaged separately and so there were no damages to the aluminum surfaces and the arms. So this unit still had potential for a full restoration with a 'like-new' end result:

I took the plates off and had a look below deck:

What I found was an original setup, always the best starting point for a successful restoration. Previous repair attempts often make things more complicated due to the introduction of 'creative human artifacts'...;-).

As usual I began with the restoration of the carriage, which usually suffers from impaired mechanical systems due to hardened lubricants. The Beogram 4000 also needs a restoration of the solenoid activated switches and the installation of a new MMC cartridge mount since the original ones were made from a plastic that has become brittle over the years and is prone to breaking off during handling of cartridges.

This shows the arm lowering mechanism in its original condition:

I removed all the moving parts and set the carriage on a soft pad to protect the fine wires that are running across its bottom side:

This shows the removed parts ready for the ultrasonic cleaner:

While the carriage is liberated it is the perfect moment to rebuild the solenoid activated switches which as usual were oxidized and bent from previous attempts to keep them working without properly extracting them:

I removed the small vertical boards that hold the switch terminals:

While the carriage is apart it is a good idea to also rebuild the board under the carriage that contains the carriage position switches. As usual the switch actuators were encrusted with some grease:

This board has similar switches like the solenoid with open contact terminals:

The red resistor on the right bottom corner is the solenoid current limiting resistor. It should also be replaced with a new one whenever this board is up since it is underrated for the application and has a tendency to go bad due to frequent overheating.

I removed all the contact terminals from carriage position and solenoid boards for cleaning and gold plating:

This shows them after the gold plating process:

I usually plate them first with a layer of Nickel for improved adhesion and then follow up with a 24K gold alloy with added metals for a hardened coating, which is suggested for plating contact terminals.

While the carriage board is up it is the perfect moment for replacing the solenoid transistor, usually a TIP41A:

I always replace it with a TIP41C, which is rated for higher voltages:

Then it was time to put things back together. This shows the carriage board with its newly gold plated contact terminals and a new solenoid resistor:

And ultrasonically cleaned plastic actuators:

This shows the restored solenoid switch PCBs:

And after installing them back in place next to the solenoid:

Next I removed the tonearm to exchange the MMC mount with a Beolover MMC cartridge mounting tab made from resilient Nylon. This shows the original mount with its wiring still in place extracted from the arm tube:

I transferred the wires to the new Beolover part:

When doing this at home, it is important to use a small tip and work quickly to not damage the plastic underneath the contact traces.

The next step was installing the new part in the aluminum tube. I usually do this with a defunct MMC cartridge in place:

This allows placing the new mount at exactly the right position to yield a flush fit of the cartridge with the arm tube (the mount actually needs to be recessed a fraction of a mm from the end of the tube). This shows the new part in place:

Like most Beogram 4000 at this point in time, this one also had a cracked plastic solenoid arm extension:

I replaced it with a Beolover solenoid arm extension for Beogram 4000:

When doing this at home it is important to apply a bit of epoxy on the threads of the bolt and once the nut has been tightened around the nut, too. This ensures that the new attachment remains in place during the fairly powerful solenoid action.

Next I re-assembled the arm lowering and carriage translation mechanisms. This shows the parts after cleaning:

Beoshiny! I always install a new damper gasket when restoring one of these units:

This ensures a consistent arm lowering speed. The original gaskets are usually hardened and a bit deformed. This can cause occasional arm lowerings without damping, which can be hair-raising if that newly restored $800 cartridge is on the arm!...;-).

I also installed a new carriage pulley precision machined from aluminum:

Beolovely! This shows the entire mechanism back in place:

There were still two more items to accomplish on the carriage. The first was replacing the original incandescent bulb in the tracking sensor. It is located in the small black plastic housing under the arms:

I removed it. This shows it bulb-up in direct comparison with the Beolover tracking sensor light source for Beogram 4000:

Its small SMD LED is located in the approximate location where the bulb filament is located on the original setup. This shows the part implanted:

The small blue box on its top is a trimmer that allows adjusting the LED intensity for fine tuning of the tracking feedback.

The second, final remaining item was cleaning and re-lubricating the pivot point of the damper-to-tonearm linkage. It is mounted on the sensor arm assembly. You can see it stick out from the v-cut that is machined into the small arm that bolts to the counterweight assembly of the tonearm:

It is telling that the arm is not seated in the v-groove. This points towards hardened lubricants impeding its motion. A common cause for arm lowering issues in vintage Beogram 400x.

I removed the sensor arm to get to the linkage.

After cleaning and re-lubricating its pivot point I gave the small copper plate on the assembly a tug with my tweezers, and as usual it came loose:

I removed the degraded double side tape from this plate and glued it back into place with a dab of epoxy.

After re-installing the sensor arm assembly and adjusting that arms to be parallel and at the right spacing my work on the carriage was concluded.

Next came the electronic systems. This shows the AC platter motor and the big original reservoir and motor capacitor cans:

These capacitors are prone to leakage after about 50 years in service:

I removed everything and cleaned up the mess from the leakages:

Before I started restoring the electronics I got the motor ready for oil-infusion of its bearings. This shows the extracted motor:

I took it apart

and submerged the clam shell housing in motor oil. Then I pulled a vacuum and strong bubbling started:

This bubbling corresponds to air being drawn out of pores from the assembly. In the case of the installed bearings this makes room for oil to diffuse into the porous Oilite material to replenish its oil reserves for shaft lubrication. This process often takes 2-3 days until the bubbling stops and the pores have been filled again.

While this process was ongoing, I started working on the main circuit board. This shows it in its original condition:

I replaced all electrolytic capacitors, power transistors, RPM relay and RPM trimmers as well as the sensor arm transistor. This shows the restored board together with the extracted parts:

While this board is flipped up it is the perfect moment to replace the two push-pull AC motor transistors. They are usually a TIP31/32 pair:

I replace them with stronger TIP41/42 for longevity:

There is one capacitor on the solder side of the board, which should also be replaced:

Here is the new one:

The smaller board in the enclosure is the power supply PCB. It also has two electrolytic capacitors and a power transistor that should also be replaced:

Done with the boards it was time to rebuild the keypad cluster. It contains the unique control logic of the deck that is built from hardwired logic gates. A very early attempt on a microcontroller, I guess...;-). To me it is one of the exciting aspects of this early 19070s design. Pretty advanced for the day. This circuit becomes visible when the keypad is taken out and put into service position:

This reveals not only the logic chips, but also the usually totally oxidized keypad switch terminals:

I extracted them for gold plating. Pretty amazing how blackend they were:

This shows them after the plating process:

Beogolden! I soldered them back into place:

Next came the upper circuit board, which features the incandescent bulbs that illuminate the position scale and the user accessible RPM trimmers:

I replaced them with the Beolover Scale Illumination LEDs and the RPM Trimmer Illumination LEDs for Beogram 4000:

As usual, the mirror for the strobe window was loose and came off easily:

I glued it back into place with a bit of epoxy.

There was still one incandescent bulb left that needed replacement, the one in the sensor arm. This shows it still installed in the small compartment at the end of the arm.

Next to it is the Beolover Sensor Arm LED Light Source together with its alignment aid. This photo shows it installed together with the extracted light bulb:

Finally, I installed the new Beolover Efficient 24V Power Supply and Main Capacitors for Beogram 4000, which elegantly replaces all the big capacitors and also updates the 24V power supply with a modern buck converter based design that is much more energy efficient than the original linear voltage regulator:

Read more about this useful upgrade here. The post discusses the advantages of the new 24V power supply and quantifies how much it lowers the emitted heat when the deck is running. Here a shot of the board from the other direction:

Next I adjusted the bias of the sensor arm transistor to the specified 1.8V:

Then I focused on the installation of the Beolover internal RIAA pre-amplifier for Beogram 4000 and the installation of a new DIN5 output cable. Someone had previously replaced the original cable with a cheap RCA jumper cable

whose other end was cutoff and soldered to the output terminals of the Beogram:

I installed a Beolover RIAA board for Beogram 4000, which solders directly to the output terminals strip:

It is powered via a wire connecting to the 24V rail on the main board:

The board can be switched between amplified and non-amplified output, i.e. this Beogram can be used together both with amps that have a Phono input and those that do not. Or it could be connected to a modern bluetooth box with line input (shudder!!...;-). I then installed a new DIN5 cable from Sounds Heavenly in the UK. It came with a nice all-metal DIN% with gold plated pins:

Now it was time to do all the mechanical adjustments. First I aligned arms and platter to be parallel and at the proper distance. Then I adjusted the floating chassis to get the platter level with the surrounding aluminum panels.

After this process was completed, I replaced the flimsy circlip that holds the adjustment screw for the counterweight in place

with a M3 nut and a washer:

This allows locking my tracking weight calibration in place so it survives shipping.

Next I adjusted the arm lowering limit to make sure the needle would miss the ribs on the platter should the arm ever be lowered without a record present due to a malfunction of the record detection circuit:

Then it was time to calibrate the tracking weight to be accurate around 1.2g, which is the specified weight for most B&O cartridges:

After these mechanical adjustments were done, I calibrated the tracking feedback:

At this point the deck was ready for a platter RPM stability test with the BeoloverRPM device:

In its 'slow' mode it records an RPM measurement every 10 seconds, perfect for the detection of intermittent RPM variations. This is the curve I measured after about 24 hrs:

This curve is pretty much as good as it gets with the AC motor Beograms. They have an exceptional RPM stability since they are driven by a precision Wien oscillator, but there is some longterm RPM drift due to temperature variations. The good news is that these changes are very slow and also pretty small, i.e. humans cannot discern them.

The BeoloverRPM has a second mode, 'fast'. In fast mode it will record an RPM value every time a platter rib passes under its sensor. These measurements allow the measurement of the wow and flutter (short term RPM changes) of the platter drive:

These measurements also typically reveal a repeating pattern corresponding to 24 rib events that is associated with small distance changes between the platter ribs. This can be regarded as a measurement artifact, or a 'fingerprint' of each Beogram platter. Each Beogram platter has a different pattern due to manufacturing inconsistencies.

This is the pattern measured during ~60 platter rotations (corresponding to a ~120 sec measurement):

The repeating 'platter patterns are superimposed with a weak sine-curve. This is basically the wow and flutter RPM change. These changes are well below the specified ±0.05% in the manual, i.e. this motor is ready to perform for another few decades!

At this point the Beogram was basically ready for a first spin, but I decided to resolve its cosmetic issues before I would test it.

First I focused on repairing the broken off red position indicator that shows the location of the tonearm on an illuminated scale above the keypad. This is a common issue with the Beogram 4000 since many people who decide to work on them do not realize how fragile this indicator is. It breaks off easily when the carriage is handled for repairs. In this case I was lucky and I found the broken off part under the keypad when I removed it for restoration. I immediately saw an easy way to fix it by designing a small 3D printed splint from translucent red filament. The printer filament I found has a very similar color like the indicator. Here you can see the fractured parts and the splint together:

I fused everything together with a bit of epoxy glue:

Looks almost like new!...;-):

And here you can see it installed:

Next came the exchange of the messed up plinth:

Luckily there are now very nice new CNC machined wood frames available designed by Christian Hakansson. I chose to use a new oak plinth with updated joints featuring splines similar to what B&O did for their refurbished Type 5513 Beogram 4002s (rebranded as "Beogram 4000c").

I removed the metal fixtures from the broken frame and transferred them to the new oak plinth. I usually use Beogram aluminum panels for aligning the metal fixtures so they have the correct height on the wood parts:

And then it was finally time to play a first record on this beautifully resurrected Beogram 4000!

I selected one of my all-time favorite records, "Sunflower" by Milt Jackson. It was released on the CTI label in 1973 as CTI6024. A perfect contemporary companion for this lovely Beogram 4000!

My favorite track is 'People make the world go round' on side 2. A very relaxing track with an almost hypnotic groove. Perfect for restoring Beograms!

Of course this great vintage vinyl was cleaned to an almost new condition using a CleanerVinyl ProXL ultrasonic cleaning setup. Here an impression of the Beogram 4000 together with this record: