Beogram 4002 (5513): Full Functional Restoration

This post describes the work done on a Beogram 4002 (Type 5513 with DC platter motor) that I received from a customer in Virginia. My initial assessment of this unit is posted here.

This shows the unit with aluminum panels and platter removed:

As usual with the DC motor Types I started with the platter motor. They all need their Oilite bearings replenished with oil under vacuum. This shows the removed motor:

I took it apart to get the bearings out. They are the two small donuts on the black pad upfront:

This shows them in my oil vat after pulling a vacuum:

The strong bubbling indicates air being drawn from the porous material making room for oil that diffuses into the material during this process. The process is complete when the bubbling stops. This can take up to three days in my experience.

While this was going on, I focused on the remaining restoration tasks. I began with removing all the moving mechanical parts from the carriage assembly. This shows it in its original condition:

And after removing the parts:

This shows the parts ready for the ultrasonic cleaner:

While they were cleaning, I took the arm lowering solenoid apart:

This is an important restoration item. The plunger of these solenoids are often magnetized, which can cause inconsistencies with the arm raising process. Often, when the arm drags across the platter during autoreturn at the end of a record, a magnetized plunger is the root cause. One can test the magnetization with a small iron set screw. If it gets attracted to the plunger, it needs to be de-magnetized:

In this case it was attracted and so I treated the plunger with my tape head de-magnetizer. After the treatment the screw was not attracted anymore:

This shows the cleaned mechanical parts:

I always install a new damper gasket:

This is important since the original ones are often deformed and/or hardened. This can cause inconsistencies with the arm lowering speed. It can be a bit hair-raising when the new $800 cartridge occasionally drops onto the platter like a rock.

After putting the mechanism together I replaced the incandescent light bulb in the tracking sensor under the arms. This shows the black bulb housing still in place:

I removed it, which revealed the tracking aperture:

As the arm moves to the left it increasingly permits light on the photoresistor beneath the aperture, which then initiates carriage motion to keep the arm straight while the record plays. This picture shows both original black bulb housing and the Beolover Tracking Sensor LED Light Source (Beogram 4002 and 4004):

The small SMD LED is located in the same space as the filament of the bulb. This makes exchange of the parts straight forward. This shows the LED assembly in place:

I also replaced the cracked original plastic pulley with a nice new Beolover Aluminum Carriage Pulley for Beogram 4002 and 4004:

Beolovely! This shows the restored assembly:

There is one more linkage whose pivot point needs to be cleaned and re-lubricated: 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 metal piece that connects to the arm counterweight:

To work on it the sensor arm assembly needs to be taken out:

As usual the small copper plate that helps the tonearm move laterally when up was only weakly attached with degraded double sided tape. I removed and cleaned it, and then epoxied it back in place:

After the epoxy cured I installed the sensor arm assembly again and adjusted the arms to be parallel and orthogonal to the rods on which the carriage travels:

Next came the RPM panel. It has two light bulbs inside that back-illuminate the RPM adjustment dials. This shows the panel removed and flipped over:

After prying off the two bulb covers the bulbs are revealed:

The two small green PCBs in front of the part are the Beolover RPM Panel LED Backlights for Beogram 4002 and 4004 (Types 551x/552x) ready for installation. Here a detail shot of one of the lightbulbs:

Clearly a non-spec replacement. I installed the LED panels. They solder directly to the solder pads of the bulbs and act as an extension of the small PCB that connects the wiring:

Here a detail shot of one of the LED panels:

The bulb covers are not obstructed by the LED panels and can be replaced after the installation:

Next I focused on the main PCB. It is best to replace the two power transistors that are mounted on the solder side of the board first when the board is still bolted in. This makes it easy to position the correctly with respect to the mounting holes. This shows the original 1IC1, usually a TIP120:

I usually replace them with stronger TIP102s:

For some reason modern TIP packages need a 100nF emitter capacitor installed in this circuit configuration to prevent high frequent oscillations that are superimposed on the 21V output. This can confuse the record detection circuit. You can see the capacitor in the above picture. It is the small yellow component soldered between the emitter pin of the transistor and a conveniently located GND pad nearby.

After also replacing 1IC4 with a TIP107 I removed the board to get to the components mounted ont he other side. This shows the board in its original condition:

A detail shot of the 'RPM section' consisting of a Siemens relay to switch between 33 and 45 and two trimmers left of it that are used to set the base RPMs:

I replaced all electrolytic capacitors and power transistors, as well as the sensor arm transistor and the RPM components: 

This shows the rebuilt RPM section with 25-turn encapsulated 5k trimmers (blue) and a new Beolover Siemens Relay Replacement for Beogram 4000, 4002, and 4004:

Next came the output PCB located under the keypad:

It contains the output grounding relay and its delay circuit:

I exchanged the relay with another Beolover replacement and installed a new delay capacitor:

I also added a switch (red) in front of the output jack that allows connecting signal and system grounds in case there is a hum after connecting to an amplifier. Connecting the two grounds often cures hum issues, especially when connecting to a RCA input.

After doing the boards and the RPM panel the enclosure was empty except for the floating chassis. I disassembled the transport locks, removed the leaf springs that float the chassis and then removed the chassis. This shows the empty enclosure with the many transport lock bushings fragments distributed around:

I vacuumed it clean and wiped everything with an alcohol drenched cloth:

Nice and clean! Then I installed new Beolover Transport Lock Bushing Set for Beogram 4000, 4002, and 4004. They come in two pieces, which makes installation very straight forward:

Simply stick one half into the lock orifice from below

and the other from the top. This shows the assembled bushing with the lock bolt already installed:

Note that some Beograms have slightly larger orifices and in such cases it makes sense to put a small bead of superglue gel on the vertical parts of the bearings when installing them. This helps keeping them secured in place when the locks are opened.

I also installed a new Beolover Main Reservoir Capacitor for Beogram 4002 and 4004 (Types 551x/552x). It can be used for both single capacitance and dual capacitance setups that 4002s may have. This unit has a dual capacitance setup, as is evident from the wiring on both ends of the capacitor can as well as the small rectifier that is bolted down with the mounting screw that holds everything together:

This shows the red alignment piece of the new capacitor assembly already in place and the unsoldered wires from the original setup:

Installation is easy. Simply tack on the white and black leads from the plug that goes to the main PCB and also connect the green AC wires to the respectively marked pads and bolt the board in:

The final step is soldering the orange wire that goes to the output board to its solder pad. The orange wire is usually of a length that it can be wrapped once around the 5th capacitor on the board for a clean installation:

This shows the leftovers of the original setup that can be discarded:

After re-installing the PCBs I briefly turned the deck on for adjusting the bias of the sensor arm transistor to get 4V at its collector:

Then I moved the trimmer below on the component side of the board:

Before making the platter height and parallelism adjustments I checked on the plastic feet of the unit. Three of them were gone:

I replaced them with rubber feed from the DKsoundparts store in Denmark. This was an important step before doing the adjustments of the floating chassis since the deck needs to be perfectly horizontal. If it is tilted due to missing feet or sitting on an uneven table it is impossible to do a proper adjustment of the platter position within its opening in the large aluminum panel.

After I achieved the correct platter to arm distance across the arms travel range (which basically means that the platter is parallel to the arms across their motion range) and had the platter flush and centered in the aluminum panel it was time to do the other adjustments:

First came the arm lowering limit. The arm should stop lowering when the tip is about 1mm above the lower parts of the platter ribs:

This is an important safety feature in case the record detection mechanism fails and the arm gets lowered accidentally onto an empty spinning platter!

After this was in place, I focused on the tracking weight calibration. My first step is always to replace the flimsy locking washer that holds the counterweight screw in place

with a M3 square nut and a washer:

This allows locking my calibration in place that it survives shipping. Then I adjusted the counterweight position to get 1.2g weight when the weight dial is set to "1.2":

This dial is notoriously imprecise and so it is good to get it to match the actual weight at the setting that is recommended for most B&O cartridges.

In the meantime the oil infusion process of the motor bearings had concluded. I extracted the bearings from the vacuum chamber:

I re-assembled the motor and installed it back in the enclosure. I put on a new Beolover Platter Belt for Beogram 4000, 4002, and 4004 and installed my BeoloverRPM device on the rim of the enclosure:

In its 'slow' mode, the BeoloverRPM is able to log the RPM in 10s intervals for extended periods of time into a serial port of a computer. This is the curve I measured over ~24 hrs:

This is as good as it gets with DC motor Beogram 4002s! A little bit of long-term drift due to temperature changes but overall very stable. This motor is definitely ready for duty again!

In its 'fast' mode the BeoloverRPM logs an RPMK measurement every time a platter rib passes under its sensor:

This allows measuring wow and flutter (the short term RPM fluctuations). The graph below shows a curve I measured during about 90s (45 rotations of the platter):

The busy zigzag pattern is a measurement artifact that results from the fact that the distance between the platter ribs varies a bit around the platter due to manufacturing imperfections. The BeoloverRPM measures the time between ribs as they pass under the sensor and then calculates the RPM from that time. Any distance changes between the ribs results in a small change in the calculated RPM. The pattern repeats every 24 points since there are 24 ribs around the platter.

The sine-wavy pattern superimposed to the 'platter pattern' represents actual RPM changes related to the DC motor feedback process that keeps the motor spinning at a constant RPM. The variations are about 0.1%, which is a typical result for Beogram 4002 DC platter motors.

The final touch of this functional restoration was replacing the grimy original DIN5 output plug. This shows the original plug:

I replaced it with a nice new all-metal plug with gold plated contact pins:

Beogolden! And then it was finally time to give this Beogram a first test spin! I selected an interesting record by Chico Hamilton from 1964 on Impulse (AS-59): "Chico Hamilton – Man From Two Worlds". I really like listening to Gábor Szabó on this one! Of course this vintage record was cleaned on a CleanerVinyl ProXL setup to restore its original sound! Here an impression of it playing on this restored Beogram 4002:

I will now play this unit for a bit longer until I get some more input from my customer about cosmetic repairs and/or upgrades.