beolover: Beogram 4002 (5523): Full Functional and Cosmetic Restoration, and Installation of Upgrades (SyncDrive, Commander Remote and Carriage Motor)

This post discusses the restoration of a Beogram 4002 (Type 5523 with DC platter motor) that I received from a customer in Louisiana. He commissioned a full restoration and upgrade with the Beolover SyncDrive, Commander remote control, and a new Beolover carriage motor for quieter operation.

This shows the final result of my efforts:

The following gives a detailed description of what it took to get there!

This shows the unit as received on my bench with the aluminum panels and platter removed:

I started out with the DC platter motor. They usually need their shaft bearings infused with fresh oil under vacuum. This shows the motor as extracted from the enclosure:

The pulley on this motor was non-spec. It was also lacking a crown, i.e. the run surface was a cylinder instead of having a bulge that keeps the belt centered. Sadly, many replacement pulley offerings on ebay etc... have this defect. This motor received a properly designed Beolover DC Platter Motor Pulley for Beogram 4002 and 4004 after the oil infusion had been completed. This shows the disassembled motor:

I put the bearings (the two small donuts on the black pad upfront in the above picture) into synthetic oil and pulled a vacuum. Immediately, strong bubbling started:

After a minute, the oil had foamed up considerably:

This suggests the bearings were pretty 'thirsty', which matches the screeching sounds the motor made when I briefly tested the unit initially. The infusion process is terminated when the bubbling stops. This usually happens after 2-3 days. So, in the meantime, I focused on the remaining restoration tasks.

First, I worked on restoring the arm lowering and carriage translation mechanisms. This shows the original condition:

I removed all the components for ultrasonic cleaning and re-lubricating:

This shows the liberated carriage:

I usually put it on a soft pad to protect the fragile wiring on the underside. I also removed the solenoid

They often have magnetized plungers from years of actuating the arm-lowering mechanism. I removed the plunger for demagnetization:

This one showed evidence of magnetization: It was able to attract a ferrous setscrew:

I worked on it with my tape head demagnetizer until it did not attract the screw anymore at close distance:

This is an important step of any Beogram restoration. A magnetized plunger is often the root cause of delayed arm lifting during the auto return at the end of a record. Not a happy moment when the new $800 cartridge from tonabnehmerservice.de drags across the record for a few inches until it finally gets lifted up!

While the parts were in the ultrasonic cleaner, I started working on the restoration of the PCBs. The main PCB has two power Darlingtons installed on the solder side. This shows 1IC1, which regulates the 21V power rail. It is usually a TIP120:

I replaced it with a TIP102, its stronger cousin:

I also installed a 100nF capacitor (yellow) between its emitter and a conveniently located GND pad. This capacitor is necessary to quench high-frequency oscillations that can occur with modern TIP transistors in this circuit configuration. The original ones do not seem to have this issue. After replacing the other solder-side-mounted 1IC4 with a TIP107, I removed the board to work on its component side. This shows the board as received:

It already had its capacitors and trimmers replaced.

Here is a detail shot of the RPM section consisting of a new relay looking suspiciously similar (I guess, being copied is the highest form of flattery...;-) to a Beolover Siemens Relay Replacement for Beogram 4000, 4002, and 4004, and the two trimmers to its left were replaced with new single-turn types:

I could not help noticing that there were some incorrect capacitor values installed:

C10 (here 2.2uF) is usually a 0.47uF or 0.33uF value.

I decided to bring all this up to 'Beolover standard,' and I replaced all electrolytic capacitors, power transistors, and the record sensor transistor with new parts. The single-turn RPM trimmers were replaced with modern 25-turn encapsulated trimmers for better adjustment accuracy. I left the relay in place since the copycat also used the exact same relay I am using on his board. So no reason to exchange it. This shows the rebuilt board:

Here is a detail shot of the rebuilt RPM section:

Next, I removed the keypad cluster and extracted the output PCB, which is located beneath the keypad.

This board features the output relay and its delay circuit:

I replaced the relay and its electrolytic capacitor, and I also installed a (red) switch that allows connecting signal and system grounds in case there is a hum in the audio signal when connecting the Beogram to an amplifier:

With the keypad out, it was a good moment to replace the incandescent bulbs in the RPM trimmer panel above the keypad. This shows the extracted panel flipped over:

Removing the covers revealed that a set of Beolover RPM Panel LED Backlights for Beogram 4002 and 4004 (Types 551x/552x) already had been installed:

The installation was less than perfect:

So I removed them and cleaned everything up for reinstallation:

For the best visual effect, these little boards should be installed flat on the original PCB and also fully centered.

I replaced the bulb covers:

It was time to reassemble the carriage. This shows the shiny,

cleaned mechanical parts back from the ultrasonic cleaner:

I always install a new damper gasket:

Replacing this gasket is an important item since the arm lowering speed depends on it. The original gaskets are usually hardened and/or deformed, and that can cause episodes of undamped arm lowering. Not a happy moment when that newly rebuilt cartridge crashes on the platter!

I installed all the other components. My customer opted for upgrading the carriage motor with a new Beolover Carriage Motor for Beogram 4000, 4002, and 4004. This shows the original motor still in place:

I unsoldered the leads and took it out. This shows the opened enclosure:

And with the new motor inserted:

It is vibration-insulated by two EPDM rubber rings that also increase the motor's diameter to match the enclosure.

This shows the new motor installed together with a new Beolover Aluminum Carriage Pulley for Beogram 4002 and 4004 and a new belt"

This unit already had a Tracking Sensor LED Light Source (Beogram 4002 and 4004) installed:

Unfortunately, the plastic housing was damaged by overtightening the screws. So I removed it, which revealed the tracking aperture:

and replaced the plastic part with a nice new one:

Next, I replaced the light bulb in the sensor arm with a Beolover Sensor Arm LED Light Source (Beogram 4002, 4004 and 4000). This shows the small compartment at the end of the sensor arm pulled out with the bulb still installed:

Next to the bulb compartment is the small LED board together with its alignment aid.

This shows it installed:

The final task on the arm lowering system was cleaning and re-lubricating the pivot point of the damper-to-arm linkage. It is located between the tone- and sensor arms. You can see it stick out from the V-cut in the small plate that is bolted to the counterweight in the picture below:

I removed the two screws that hold the sensor arm down. Then I removed the linkage:

After cleaning and lubricating the linkage, I put everything back together and then reattached the little copper plate that helps the arm move laterally when it is in its up position:

The final step was adjusting the arm alignment to get everything perpendicular to the rods the carriage travels on. I now always use my very convenient recently developed Beolover Arm Alignment Tool for Beogram 4000, 4002 and 4004:

It makes it a snap to align the sensor arm base with the rods and then the sensor arm. Once that is in place, the tonearm can be parallelized using a caliper.

This concluded my work on the carriage. It was time to empty the enclosure and vacuum

out the remaining transport lock bushing fragments. They need to be removed since they can impede the free movement of the floating chassis. This shows the cleaned-out enclosure:

Then it was time to install a set of new Beolover Transport Lock Bushing Set for Beogram 4000, 4002, and 4004 on the floating chassis. The three bushings come in two halves each. This makes installation very easy. Simply insert one of the halves from below

and the other from the top:

Note that some Beograms have slightly larger orifices for the bushings. It is generally a good idea to use a bead of superglue gel on the vertical parts of the bushing halves to lock them in place.

This shows one of the transport locks partially re-assembled around the new bushing:

After completing the transport locks, I installed a Beolover Main Reservoir Capacitor for Beogram 4002 and 4004 (Types 551x/552x). This shows the original single capacitance setup:

Since this Beogram came with a standard reservoir capacitor, i.e., the installation of the new Beolover assembly was easy. All I had to do was solder the white and black wires to the respectively labeled solder pads on the capacitor board:

My next task was replacing the very grimy power cord:

After the cord enters the enclosure, it connects to the fuse box. This shows the box opened up:

It is good to leave the fuses in place when soldering connections in the fuse box. The heat can loosen the attachment of the terminals to the plastic, and the fuses help keep things straight until the plastic hardens again. I unsoldered the power cable:

Then I removed the screws that hold the fuse box to the enclosure bottom and flipped the box around. After removing the cover, the wiring can be seen:

Before the old cable can be removed, the cable gland that secures the cable against getting pulled out needs to be extracted from the feedthrough orifice. This can be done with suitable pliers. Pressing the locking piece further into the cable allows pulling the gland out:

Then the gland can be removed from the cable:

Installation of the new cable is in reverse: After feeding it through the enclosure orifice, it can be pushed into the fuse box and soldered to the terminals:

This shows the fuse box bolted back in and the cable routed to the orifice:

For installing the gland on the new cable, a 'bigger gun' is necessary since the cable needs to be deformed so that the gland can reach its design diameter:

Once the gland has been pressed together suitably, it can be installed in the orifice:

Beolovely! On to replacing the equally grimy RCA output cable:

Luckily, I had an original B&O fully shielded RCA cable from a recent partout of a hopelessly damaged Beogram 4004:

These original cables are of great quality compared to most things they sell these days: Multistranded signal wire and a fully braided signal return in each separately insulated wire. Nowadays, you can count yourself lucky if there is an aluminum foil shield. Two RCA jumper cables that I initially bought on Amazon for this project, with the plan to cut the plugs on one side for installation, had no shielding at all. They looked good from the outside, but on the inside, there were just two individually insulated straight wires for signal and return. I guess this can work as long as the cable is short enough and the external stray fields from the environment are not very strong. In such cases, the EMI cancels out on both of the wires due to their close proximity and the opposing direction of the current.

Anyway, my first step was cutting off the corroded original plugs for replacement:

For the record: the yellow wire/gray plug is the left channel if the cable is connected in the factory way on the other end.

I installed two nice new all-metal RCA plugs with gold-plated terminals:

This shows how I implemented it on the other end:

In the meantime, the oil infusion of the bearings had concluded. I extracted the bearings from the oil vat in the vacuum chamber:

Then I re-assembled the motor and installed a new Beolover DC Platter Motor Pulley for Beogram 4002 and 4004:

Note the bulge in the center of the run surface. This is called a crown and serves the purpose of keeping the belt centered when the pulley turns. If the shape is a flat cylinder, the belt will scrape either on top or on the bottom and make noises. This, of course, also affects wow and flutter. I installed the motor in the Beogram and ran a 24 hrs RPM stability measurement with my BeoloverRPM device:

The BeoloverRPM has two operational modes. In 'slow' mode (shown above), it measures the RPM in 10-second intervals and sends the data to a serial port of a computer, where it can be recorded with any generic terminal software. This allows plotting the RPM over long periods of time using Excel or similar software. This shows the result of my 24 hrs measurement:

This is quite a nice result for any Beogram DC platter motor! As good as it gets! Next, I collected some high-resolution data in the 'fast' mode of the BeoloverRPM:

In this mode, the device sends an RPM measurement every time a platter rib passes underneath the sensor. This results in 24 RPM measurements per platter turn (there are 24 ribs). This allows visualizing short-term RPM changes caused by the feedback-based motor control circuitry. This graph contains the data covering ~35 platter turns (~70 sec):

The prominent zig-zag pattern is a measurement artifact that comes from the fact that the spacing of the platter ribs around the platter is slightly irregular due to manufacturing imperfections. This generates a repeating pattern for every platter turn (sort of a 'platter fingerprint'), which is superimposed on the real RPM changes that are introduced by the feedback system that keeps the motor RPM stable over time. This real RPM change is essentially the sine-wave-like pattern that modulates the zig-zag pattern. An evaluation of the wavy component yields a wow and flutter estimate of about 0.1%.

This is 2x the 0.05% value stated in the specs list in the service manual. This difference is most likely systematic due to the entirely different way wow and flutter were measured in the 1970s when these turntables were produced. I see it for all Beogram motors that I restore. Back then, the measurement was carried out with a test tone on a test record. In these measurements, deviations from the tone center were measured with an analog spectrum analyzer and then converted into a wow and flutter number. It should be pointed out that this discussion is pretty academic in the first place since humans typically start recognizing frequency fluctuations above the 0.7% threshold, i.e., the RPM fluctuations of this Beogram are well below this value, whether the number is 0.05% or 0.1%. This motor is definitely ready for duty again!

After this successful test of the motor, I did the electrical adjustments: First,

I adjusted the bias of the sensor arm transistor to yield 4V on the collector:

Then I moved the adjusted trimmer below deck to the component side:

Then it was time to measure the sensor response:

The above oscilloscope trace was measured on the collector of the sensor arm transistor while I spun the platter manually with my finger. Each dip corresponds to a black platter rib passing underneath the sensor. The measured amplitude is 7V, which is a very solid result. This record detection sensor is in great shape again!

This Beogram was nearing completion, and it was the moment for doing all the mechanical adjustments to align the platter and arms and get the floating chassis situated properly. But before I was able to do that, I still needed to install the new wood plinth and keypad so I could seat the aluminum plates properly, a prerequisite for doing the adjustments.

First, I worked on the wood plinth: I removed the metal pieces from the original wood frame by baking the frame for an hour at 250F in my oven. This softens the old adhesives, and one can cut the pieces from the wood with a carpet knife. This was followed by soaking the parts in isopropyl alcohol overnight and then rubbing off the old glue. After the metal pieces were clean, I applied 3M adhesive to them:

Then it was time to attach the metal pieces to the new 4000c style oak frame. I use two of the small aluminum plates for aligning the metal piecers with the frame. The aluminum plates have exactly the thickness needed for this process:

The challenge is to get the metal pieces all the way into the corners while they are sticky. My solution is to use strips of parchment paper to keep one side from sticking while the other is pushed all the way into the corner and pressed to the wood. Once this bond has been made, the parchment paper can be removed, and the other leg of the piece can be pressed into place using the aluminum surface as a guide.

The other side is done the same way:

This shows the completed transfer to the new oak frame:

Then it was time to replace the worn keypad with a newly restored one (see here if you are interested in getting your keypad fixed). This shows the original keypad and restored replacement in direct comparison:

It is obvious that the original keypad is way too shiny, indicating that the coating had been removed.

The original keypad had cracked RPM panel alignment pieces. Luckily, there are exact reproductions available at the dksoundparts store in Denmark. This shows old and new in direct comparison:

The new pieces do not come with the metal springs installed, so one has to transfer the original springs:

It is an easy process to put them in place:

This shows the new pieces installed on the new keypad assembly:

When I was about to stick the keypad PCB into the new assembly, I realized that the plastic plunger assemblies were all caked up with old lubricants. So I removed them and put them in the ultrasonic cleaner for a few minutes. This shows the cleaned parts:

I plugged them back into the PCB:

This shows everything back together:

With the keypad out, it was the perfect moment to install the first upgrade, the Beolover Commander Remote Control for Beogram 4002 and 4004. The module plugs directly into the keypad header on the main PCB:

Once the Commander board is installed, the keypad cluster can be seated:

The LED auto-repeat indicator of the Commander system bolts in under the mounting screw of the keypad.

It is a good idea to hold the RPM panel wiring in place with a strip of adhesive tape:

This prevents interference with the harness connecting the small LED panel and the RPM panel can be seated properly:

With frame and keypad in place, I started the process of aligning arms, platter, and floating chassis to get the platter parallel to the arms across their travel, and the platter flush with the surrounding aluminum panels. This can be an iterative process that takes a few passes to yield proper alignment.

Once this is completed, the arm adjustments can be done. I usually replace the flimsy locking washer that holds the counterweight screw in place

with a square M3 nut:

This allows locking my tracking weight calibration in place so it can survive the shipping process. Before I did the weight calibration, I adjusted the arm lowering limit:

The tip should stop about 1 mm above the lower parts of the platter ribs as shown above. Then I used a digital weight gauge to adjust the arm counterweight to get 1.2g weight at the 1.2g mark of the adjustment wheel:

The adjustment wheel is not very precise, and it is a good idea to check the tracking weight occasionally with a gauge to make sure the weight is still correct.

Then I adjusted the tracking feedback:

My customer decided to replace the original platter motor with the SyncDrive. The SyncDrive puts DC motor Beograms on par with the older AC motor models in terms of RPM stability and wow and flutter, while giving them the absolute RPM accuracy of the later 8000/8002 models. This shows the SyncDrive installed:

Time to give this restored Beogram a first spin! I selected one of my favorite CTI albums: Stanley Turrentine's "Cherry", which he released in 1972 together with Milt Jackson (CTI 6017). I love the cover art of CTI albums! This shows this lovely album playing on this perfectly restored Beogram 4002:

The Beogram played perfectly!

It was time to install the new hood and aluminum trim to complete this project! I used a razor blade for prying off the side parts of the aluminum trim. This revealed the mounting screws:

This shows the new Dust Cover for Beogram 4002, 4004 and 6000 and reproduction aluminum trim together with the liberated metal hinge part:

A while ago, I cracked a hood due to interference between plexiglass and metal hinge. For this reason, I always test new hoods if they scrape on the metal or not before I install them. This hood passed with a minimum gap of about 1 mm:

There is a little flaw in the design of these new hoods: They have a recess in the plexiglass just where the aluminum trim bends down on the sides. That makes it difficult to get a precise bend of the trim since there is a void right at the edge. I alleviate this issue by epoxying 3D-printed plastic bits into the upper end of the recess to fill the void.

Once the epoxy is hardened, I trim the bits with a razor blade to get them flush with the plexiglass edge.

After this design improvement, it was time to install the hood! I removed the hinge assembly and set up my alignment tools for the aluminum trim:

I used a strip of blue tape to make an alignment mark:

Then I bolted the hood in again. This time I put some white glue into the threads to prevent the bolts from coming loose. They cannot be tightened very much since it is easy to crack the plastic when the bolts are too tight: