Beogram 4002 (5513): Full Functional Restoration and a Test Spin with Earl Klugh

This post discusses the work done during the restoration of a Beogram 4002 that I received from a customer in California. My initial assessment of this unit is posted here. 

This shows the unit at the beginning of my process with the aluminum panels and platter removed:

As usual for this type of Beogram I started with the restoration of the DC platter motor. Most have dry shaft bearings that need to be re-infused with oil under vacuum. This process usually takes 2-3 days and so it is a good idea to start it at the begin of the restoration process. This shows the removed motor:

I completely disassembled it to get to the bearings. They are the two small donuts on the black pad upfront:

I submerged the bearings in synthetic oil and pulled a vacuum. Immediately strong bubbling started:

The bubbling represents air being drawn from the porous bearing material. As the air leaves oil can diffuse into the evacuated space. The bearings are full again when the bubbling stops.

While this was going on, I focused on the remaining restoration tasks. First came the restoration of the carriage. This shows it in its original condition:

I removed all moving parts that constitute the arm lowering and carriage translation systems. They usually are encrusted with hardened or wrong lubricants, which often has adverse effects on the operation of the turntable. This shows the liberated carriage with the parts removed:

First I tended to the arm lowering solenoid:

In many cases the plunger is magnetized, which can delay arm lifting. This is often the root cause when the needle is dragged across the record during the automatic arm return at the end of a record.

I removed the plunger:

I tested it with a black steel set screw. If the plunger attracts it like in this case it is magnetized:

I treated the plunger with my tape head de-magnetizer and after that the set screw did not get attracted anymore:

Then I put everything (except the coil) in my ultrasonic cleaner. This shows the parts as extracted

and after the cleaning process:

Beoshiny! Then it was time to re-assemble the mechanism. First I installed a new Damper Gasket for Beogram 4000, 4002, and 4004 in the damper plunger:

This is an important detail of my process. The original gaskets are often deformed or hardened, and that causes inconsistencies in the arm lowering speed. It can be pretty harrowing when the new $800 cartridge crashes onto the record!...;-).

After putting the arm lowering and carriage drive mechanisms back together I also replaced the cracked original plastic pulley with a new Beolover Aluminum Carriage Pulley for Beogram 4002 and 4004 and a EPDM belt:

Beolovely! This shows the entire setup back together:

There was one more mechanical item that needed to be addressed, the damper to arm linkage. It is often the reason for arm lowering issues due to hardened lubricants on its pivot point. You can see it stick out from the v-cut in the small metal plate that is bolted to the back of the counterweight in this photo:

In order to remove the part the sensor arm needs to be liberated:

I cleaned and re-lubricating the pivot point and glued back the small copper plate that helps smoothing the lateral arm motion when the arm is up. Then it was time for replacing the incandescent light bulb in the tracking sensor under the arms. The bulb is in the small black housing in the center of this picture:

I removed the bulb housing, which revealed the tracking sensor aperture:

This shows the original bulb setup on the left and the Beolover Tracking Sensor LED Light Source (Beogram 4002 and 4004) on the right:

The small SMD LED on the board is in the same spot like the bulb filament, making the exchange straight forward. This shows the LED part in place: 

This concluded my work on the carriage assembly and I moved on to rebuilding the circuit boards. First came the main PCB. It is best to replace the two power transistors that are mounted on the solder side first. This makes it straight forward positioning the replacements correctly. This shows one of them, 1IC1, which is configured as the voltage regulator for the 21V rail. It is usually a TIP120: 

I replaced it with a TIP102 that has a higher current capability. I hope this will make it last longer! For some reason modern TIP packages need a 100nF capacitor at the emitter in this circuit configuration. Without it there is often a high frequent oscillation superimposed on the power rail that confuses the record detection circuit. I usually add the capacitor (yellowish package north of the TIP next to the mounting screw) between the emitter pin and a convenient GND terminal nearby:

After replacing 1IC4 with a TIP107 I removed the board. This photo shows it in its original condition:

And here a detail shot of the 'RPM section' consisting of the RPM switching relay and the two RPM calibration trimmers to the left of the relay:

I went ahead and replaced all electrolytic capacitors, power transistors, RPM relay and trimmers, and the sensor arm transistor that often lost part of its gain. This shows the rebuilt board and the extracted parts:

In the RPM section I implanted a new Beolover Siemens Relay Replacement for Beogram 4000, 4002, and 4004 and two 25-turn encapsulated trimmers for improved consistency and adjustment precision:

Then it was time to take the output PCB out. It is located under the keypad assembly. This shows it in its original condition:

The muting relay was also a Siemens type:

I replaced the relay and the capacitor that is responsible for the time constant of the relay delay. I also installed a (red) switch that allows connecting signal and system grounds (in case there is a hum issue, especially when connecting to RCA based receivers:

At this point pretty much everything had been removed from the enclosure except the floating chassis. This made it the perfect moment for removal of the chassis and the installation of a new Beolover Transport Lock Bushing Set for Beogram 4000, 4002, and 4004. This shows one of the 'beautifully' degraded original bushings:

After removal of the floating chassis the enclosure was empty except for the many bushing fragments:

I vacuumed everything out:

And then it was time to install the new bushings. They are composed of two parts, one that pushes into the orifice from below and the other from the top. This makes it very easy to install them. This shows one of them in place with the lock screw installed already:

After re-installing the floating chassis with its new bushings I replaced the reservoir capacitor with a new Beolover Main Reservoir Capacitor for Beogram 4002 and 4004 (Types 551x/552x). This shows the original setup before I removed it from the enclosure:

This Beogram 4002 has the earlier double-capacitances (4000uF and 1000uF) capacitor installed. In this configuration the 4000uF capacitance serves to stabilize the 21V power rail of the main PCB, while the 1000uF capacitance is used for stabilizing the optional CD-4 board that could be installed to make the Beogram 4-channel capable. In later 4002 this was replaced by a single 4000uF capacitor that did both.

The Beolover capacitor replacement can be installed in both 4002 versions. For the double capacitor setup it is best to remove the green AC leads, the orange lead coming from the output board and the white and black leads coming from the PCB plug from the capacitor can:

The next step is to remove the old capacitor with the rectifier attached:

Then the green, white and black leads are soldered to the new board after which the new board can be bolted in:

It is best to tack the orange lead on after the board has been installed. Usually the orange lead can be wrapped around the capacitor in the back right and then tacked on. This makes for a nice and clean setup:

Next I installed the remaining parts. And then it was time to adjust the new bias trimmer of the sensor arm transistor to get 4V at the collector of the transistor:

After the adjustment I moved the trimmer to the component side of the board. 

Then I replaced the incandescent light bulb in the sensor arm with a Beolover Sensor Arm LED Light Source (Beogram 4002, 4004 and 4000). This picture shows the small compartment at the arm pulled out with the original bulb still installed. The LED assembly can be seen to the right:

And here a shot of the LED board installed:

This is how the B&O logo looks like illuminated by the LED:

Very 'original'! A result of me using a warm white LED that emits enough red photons to mimick an incandescent bulb.

There were still two remaining bulbs that needed to be replaced. They were located in the RPM panel that sits above the keypad. This shows the panel removed and flipped around:

After removal of the two bulb covers, the bulbs can be seen in their aluminum holders:

The two Beolover RPM Panel LED Backlights for Beogram 4002 and 4004 (Types 551x/552x) are in front of the panel ready for installation. They solder directly to the solder pads of the bulbs, i.e. function as an extension of the small PCB that makes the connections to the bulbs and the trimmers in the panel:

The LED panels do not obstruct the bulb covers, which can be installed like before:

This shows the 33 RPM LED backlight in action:

Looks very much like an incandescent bulb! Beolovely!

Now it was time to focus on the remaining adjustments. The first step is usually to align arms, platter and subchassis to achieve a 23 mm top-of-the-arms-to-platter distance and to get the platter and arms parallel, while leveling the subchassis to get the platter flush with the surrounding panels. This can be a pretty tedious and iterative process, depending on how out of alignment things are. I usually start with getting the aluminum panels properly aligned and settled on their alignment pins together with the keypad. Then I get the arms parallel and in 23 mm distance with the aluminum panels. Then the platter can be adjusted to be in the same distance. If everything is done right at that point everything is parallel and in the right distance.

After the above was in place, I focused on the tonearm adjustments. First, however, I replaced the flimsy circlip that holds the counterweight adjustment screw in place

with a M3 square nut and a washer:

This allows locking in my calibration so it survives shipping.

Then I adjusted the counterweight to get 1.2g tracking weight at the 1.2g setting of the adjustment wheel:

The adjustment wheel scale is notoriously imprecise, so I try getting it calibrated at the 1.2g point, which is the trackging weight for most B&O cartridges. Generally, it is best to use a digital tracking weight scale occasionally to check if things are still right.

The next step was adjusting the arm lowering limit. This is an important adjustment since it is the last resort to save the needle if the record detection circuit fails and the needle gets accidentally lowered on an empty rotating platter. The limit needs to be adjusted that the needle misses the lower parts of the ribs by about 1 mm:

In the meantime the oil infusion process had come to an end. I extracted the motor bearings from the vacuum chamber:

I re-assembled the motor and implanted it back in the Beogram. Then I ran a 24 hrs RPM stability test with the BeoloverRPM device:

The BeoloverRPM measures the time between platter ribs passing under its sensor. From this measurement the RPM is calculated. In its 'slow' mode the BeoloverRPM sends an RPM measurement every 10 seconds to the serial port of a computer. This allows measuring the RPM over long periods of time, which is great for detecting intermittent RPM variations. This is the curve I measured after about 24 hrs:

This is as good as it gets for the DC motor Beograms! The BeoloverRPM has a second mode, 'fast', which sends a measurement every time a rib passes under the sensor:

This high resolution data allows seeing the feedback control mechanism in action. This graph shows a measurement over about 43 rotations of the platter (~1.5 min runtime):

The observed graph is a superposition between a slow sine-like wave and a fast repeating pattern. The fast pattern is a measurement artifact caused by the slightly varying distance between the ribs around the platter. It repeats exactly every 24 data points, corresponding to the number of ribs.

This is a manufacturing 'defect' that can be regarded as a 'finger print' that is unique to each platter. This particular platter has a very clear pattern meaning that the variation of the rib distances is smoothly in- and decreasing around the platter.

The sine-wave like superimposed pattern reflects actual RPM variations. An evaluation of this line shape reveals RPM variations of about 0.1%. This is about double the <0.05 number stated in the service manual, but this may well be a result of the entirely different measurement methods used here and back in the 1970s, when digital technology was still in its early beginning and wow and flutter was measured with test records and analog frequency analysis. In any event these variations are much too small for humans to notice. Only RPM variations above about 0.7% can be detected by most people.

Before it was time for a first test spin of this restored Beogram 4002, I needed to replace the badly corroded original RCA plugs (this deck is one of the few 'factory RCA' units that seem to be around):

I replaced them with two nice all-metal new RCA plugs with gold plated contact terminals:

Beogolden! I usually fit the plugs with 3D printed red and black inserts for identifying right and left channels:

And then it was finally time to sit back and spin a nice record! When buying records on discogs recently, I found a very smooth record by Earl Klugh when I checked what else a seller had (free shipping and a great way of discovering new music!...;-): "Magic in Your Eyes" (UA-LA877H). He recorded it in 1978, which makes this a perfect complement for the Beogram 4002. Perfect music for listening while restoring Beograms! Smooth and calm! Perfect! Of course this record was ultrasonically cleaned on a CleanerVinyl ProXL setup after I received it. Here a picture of this album playing on this newly restored Beogram 4002:

My customer decided to get this unit also cosmetically restored with a new hood and keypad. It will also receive the Beo4 enabled Beolover Commander remote control system and the Beolover internal RIAA pre-amplifier so it can be smoothly connected to more modern amplifiers without Phono input. Stay tuned!