Beogram 4002 (5513): Complete Functional Restoration and Installation of the Commander Remote Control Module

This post is the follow up to an initial post I made about a Beogram 4002 (5513) that arrived from West Virginia a while ago. In the above post I discussed the overall condition of this unit. Here I will show what was done to the unit to bring it back to like-new performance.

This shows the unit as I received it:

As usual, I first rebuilt the carriage. Most Beograms of this vintage have hardened lubricants that need to be removed and replaced. I removed the moving components of the arm lowering mechanism, the rods the carriage slides on, and the threaded rod that drives the carriage:

This shows the cleaned parts:

The next step was to replace the tracking sensor light bulb with a LED based replacement. This shows the original setup:

I removed the original bulb housing and installed the Beolover LED replacement. It has a built in trimmer (blue) that allows regulating the brightness of the LED:

The trimmer is useful for fine-tuning the tracking sensor responsiveness.

Another 'carriage task' is the replacement of the usually cracked original plastic pulley. This shows the precision machined aluminum replacement:

Beolovely! On to the damper to arm linkage that has its often stuck pivot point on the sensor arm assembly. This shows the linkage on the removed sensor arm. It lacked the circlip that holds the linkage on its pin. 

I replaced the missing clip with a new one:

As usual, the small copper plate that is glued to the sensor arm base to reduce friction of the of the upper limit adjustment screw for the tone arm fell off when I worked on the assembly:

It is originally attached with degraded double sided tape. I cleaned the tape residues off and reinstalled it with a dab of epoxy:

The next step was to rebuild the PCBs. This shows the main PCB in original condition:

This detail shot shows the 'RPM section' of the board with the RPM relay and the corroded RPM trimmers:

I replaced these parts with modern ones, to ensure RPM stability and easy calibration with encapsulated multi-turn trimmers:

I also replaced all electrolytic capacitors and the sensor arm photodetector transistor:

I also replaced the power transistors: This shows, as an example, the replaced 24V rail TIP120 Darlington transistor:

Next in line was the output board with the output muting relay and its delay circuit:

I replaced the relay and the electrolytic capacitor that is part of the time constant of the delay circuit. I also implemented a switch that allows connecting system and signal grounds in case there is a hum problem (often the case with RCA versions, which this Beogram is):

When I took out the board I realized that the clamp that holds the output cable in place as well as the PCB upper end was cracked:

This happens frequently in these models, and so I have a replacement part available, which I installed:

While I had the boards out It was a good moment to have a look at the transport lock bushings, which are usually degraded in this Beogram vintage. This shows the left bushing after removing the upper part of the transport lock:

Since the fragments of these degraded bearings are often distributed all over the enclosure it is necessary to remove the floating chassis and clean out the debris. Otherwise they can get lodged beneath the floating chassis and impede its free movement, which is detrimental to the main purpose of the floating chassis: Vibration damping. I removed the chassis and also the original reservoir capacitor shown here:

This shows the emptied enclosure:

After installing the new bushings (3D printed replacements - this shows again the left lock as an example)

and re-installing the chassis it was time to put a new reservoir capacitor in place:

This Beogram is a version that is ready for CD-4 upgrade, i.e. it has a dual capacitance reservoir capacitor, which needs to be replaced with two individual modern capacitors, since dual capacitance models seem to have gone out of fashion these days.

The next step was the replacement of the two light bulbs in the RPM adjustment panel above the keypad. These bulbs illuminate the adjuster scales and have the potential to cause RPM variations since they heat up the potentiometers inside this panel. This shows the original bulbs installed:

I replaced them with the latest iteration of the Beolover RPM panel LED assemblies:

They solder directly to the wire terminals of the bulbs. Then it was time to replace the last of the 4 incandescent bulbs of this Beogram, the sensor arm bulb. This shows the original bulb in place with its replacement next to the arms:

This shows the LED assembly in place and 'in action':

Next came the various mechanical adjustments like floating chassis position, arm parallelism, platter alignment, and finally the adjustments on the tonearm. This shows the original circlip on the counterweight adjustment screw:

This arrangement is a bit flimsy and does not hold the counterweight firmly in position. Therefore, I usually replace the circlip with a M3 square nut:

Then it was time to calibrate the tracking weight with a digital gauge:

Once the weight was calibrated I adjusted the arm lowering limit:

This is an important adjustment since it ensures that there is no damage to the stylus should the arm drop on the empty spinning platter due to a malfunction in the record detection circuit.

Then I calibrated the RPM for 33 and 45 settings and adjusted the tracking feedback. At this point the only thing separating me from a test spin were the very corroded original RCA plugs:

I replaced them with nice all-metal gold plated units:

Then it was time to install the Beolover Commander remote control module, which was recently redesigned (see here for more info):

The Commander is an important addition since it enables operating the Beogram entirely without touching the precious keypad. These keypads often loose their coating due to contact with the acids and fats in the skin. The Commander uses an Apple remote and it mirrors all functions of the keypad, plus it adds a dynamic slow/fast scanning feature and an auto-repeat mode, similar to that found in the later Beogram 8000 and 8002. 

Then it was finally time for a test spin. I selected one of my favorite CTI recordings, "Cherry" by Stanley Turrentine and Milt Jackson (CTI 6017). It was recorded in 1972. A perfect period-correct match for this beautiful Beogram 4002! Of course this album was cleaned ultrasonically before play with on a CleanerVinyl ProXL setup. 

I will now play this Beogram for a couple of weeks aiming to make as sure as possible that there are no intermittent issues. Then it will be time to send it back to its owner in West Virginia!