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Beolover SyncDrive: DC Platter Motor Replacement for Beogram 4002 and 4004 (Type 551x and 552x)

Late Beogram 4002 and the 4004 (Types 551x and 552x), which have DC platter motors instead of the earlier synchronous AC motors usually suff...

Thursday, August 24, 2023

Beogram 4002 (5513): Full Functional Restoration and Installation of Beolover Commander Remote

This post describes the work I did on the Beogram 4002 (Type 5513) that I recently received from California. See here for my initial assessment of this unit.

This shows the unit with the aluminum panels off as I received it:

As usual I started with the platter motor since the oil infusion of the bearings can take up to 72 hrs. This shows the extracted motor:
I took it apart and removed the bearings:
The bearings are the two small donuts on the black pad. I immersed them in motor oil and pulled a vacuum. Immediately vigorous bubbling started:
The bubbles coming from the bearings are air that is drawn into the oil due to the vacuum. This makes room for oil to diffuse into the porous bearing material. While this process was going on I focused on the remaining restoration tasks. First I removed all 'motion critical' parts from the carriage assembly for cleaning:
This shows the removed parts:
And after cleaning in an ultrasonic bath:
Beolovely! Then I put everything back together. A critical update is the replacement of the damper gasket:
They tend to harden over time, which can make the arm lowering process inconsistent. Another task to do while working on the carriage is the replacement of the tracking sensor light source. The original incandescent bulb sits in the black box under the arms:
I replaced it with a Beolover LED based replacement (left):
The SMD LED is placed in the same approximate location as the filament of the original light bulb.
This show the LED replacement implanted:
And here a shot of the restored carriage assembly:
There is one more mechanical part that needs to be re-lubricated. It is the damper to arm linkage, whose pivot point is located on the sensor arm assembly. This shows the arms from the back. The linkage pokes out via the V-shaped cut on the small arm that is attached to the counterweight assembly:
The re-lubrication of the pivot point requires that the sensor arm assembly is removed:
While working on this I also re-glued the small copper plate that eases the lateral movement of the tonearm when it is up. This small plate usually is about to fall off since it is only attached with decaying double sided tape:
This completed my work on the carriage. 

The next step was restoring the PCBs. As usual I started with replacing the two power Darlingtons that are mounted on the solder side of the main PCB. It is best to replace them while the board is still installed, which makes their correct placement easy. This shows the original TIP125 (IC4) which is responsible for activating the solenoid:
I replaced it with a stronger TIP107 since this transistor is probably the most stressed electronic component of this circuit:
After also replacing IC1, I removed the PCB:
This is a detail shot of the 'RPM section' comprised of the original Siemens RPM relay and the two RPM adjustment trimmers in the corner:
I replaced the relay and the trimmers, all electrolytic capacitors and the remaining power transistors (especially replacing the original H-bridge transistor is advisable - they often go bad once the decks are used again for a while). This shows the rebuilt board:
And again a detail shot of the RPM section:
The new 25-turn precision RPM trimmers are installed in a way that the adjustment screws are accessible from the solder side of the board, allowing adjustment while the board is installed.
The next step was restoring the output board. This shows it in its original condition:
And with a new output relay, a new capacitor for the relay activation timing, and a switch (red) that allows connecting system and signal grounds in case there is an audible hum during record playing. This feature is often handy if a Beogram is used with an amplifier with RCA inputs:
After having removed the boards and the keypad I also removed the main reservoir capacitor. This shows the original unit:
It is a dual-capacitance design, which was used for Beograms that could be upgraded with a CD-4 output board. I also removed the plinth, which had a metal fixture that was about to fall off:
This shows the completely empty enclosure after vacuuming out all the fragments from the completely decayed transport lock bushings:
It is important to remove such fragments since they can get lodged under the floating chassis and impede its floating motion.
After the enclosure was prepared I started the re-assembly of the components. First I installed new transport lock bushings. My replacement bushings are designed in two parts. This makes it very easy to install them: 
Simply stick one half into the lock opening from the bottom, and the other from the top, and that is it:
This shows one of the locks re-assembled:
After the floating chassis was back in place I installed a new reservoir capacitor assembly. Since the original dual-capacitance units are no longer manufactured, I came up with a 3D printed replacement part that holds two standard capacitors:
This shows the assembly installed:
The next step was installing the re-guled plinth. Since the deck had lost four of its plinth guidance washers, I replaced them with 3D printed nylon replicas:
This shows one of them installed:
Next I focused on replacing the remaining incandescent light bulbs with LED based assemblies. This shows the sensor arm compartment pulled out from the arm tube. Next to it is the Beolover LED replacement with its alignment template:
I removed the bulb and installed the LED board:
This shows it in action:
The remaining bulbs were in the RPM adjustment panel. This shows it belly up. The bulbs are behind the two covers on the back:
This shows the bulbs after I removed the covers:
I unsoldered the bulbs and pulled them out. The two LED replacement boards are shown up front:
They solder directly to the bulb terminals:
They do not interfere with the original covers, i.e. they can be replaced:
Now it was time to focus on adjustments:
The first step is usually to adjust the platter that it is parallel to the arms travel and at the correct height. Once that is done the floating chassis needs to be adjusted that the platter is flush with the aluminum panels and centered inside the round opening in the main panel. This can be a bit of a challenge and several iterations are necessary until everything is straightened out properly. 

After this is done one can focus on calibrating the tracking weight as well as the arm lowering limit. My first step is usually to replace the flimsy locking washer on the counterweight screw with a nut, which allows locking the calibration in place so it survives shipping. 
On this deck someone had beaten me to this issue by glueing the screw into place:
Messy! I used the hot air blower of my soldering station to soften the glue, which finally allowed me to remove it and with that the screw so I could install the nut:
Then I was able to calibrate the tracking weight to yield the proper 1.2g when the small weight dial is set to 1.2. The scale on this dial is notoriously imprecise, i.e. it is best to check the weight occasionally with a digital scale:
After the tracking weight was properly set, I adjusted the arm lowering limit:
This is an important adjustment since it is the 'fail safe' in case the control system develops an issue and the arm gets lowered on an empty spinning platter. The limit prevents a crash of the needle onto the ribs of the platter.
On to electronic adjustments. First I adjusted the bias of the sensor transistor to get 4V at its collector:
After the trimmer was set, I removed it and soldered it into place 'below deck' on the component side of the main board:
Then I adjusted the tracking sensor feedback:
At this point the bubbling of the motor bearings had stopped, and I extracted them from the oil:
Then I reassembled the motor and implanted it back into the enclosure. Then it was time for a 24 hrs RPM stability test using the BeoloverRPM device:
The BeoloverRPM allows measuring the RPM in 10s intervals for extended periods of time. Ideal for detecting intermittent RPM variations. In this case the motor performed perfectly and I measured this curve after about 24 hrs:
This is probably one of the best RPM curves I ever measured on a DC motor Beogram! Beolovely!
Unfortunately, the measurement of the sensor response was decidedly un-Belovely:
The curve was flat, indicating that the sensor did not respond at all!
I removed the sensor compartment and had a closer look. What I found was that one of the electrodes of the photo cell that measures the reflected light from the platter had come off:
I removed the photo cell:
This will need some more attention down the road. I decided to 'borrow' a restored sensor compartment from one of my working Beograms and install it in this unit so I would be able to run and test it, while I work on a solution for the broken photo cell. With the replacement sensor compartment I was able to measure an excellent sensor response, indicating that the circuit works well:

The final step of the functional restoration was the replacement of the corroded original DIN5 plug
with a modern all-metal unit with gold plated terminals:
My customer wanted a Beolover Commander remote control module installed. This shows the module in place:
It is a simple plug-and play installation, which can easily be done 'in the field' without soldering or other special tools. Please, see here for more information.
Since this deck came with a hood that was beyond repair, a new hood needed to be installed. This shows the replacement hood (from the beoparts store in Denmark) with a properly labeled reproduction aluminum trim strip:
I installed the hood on the original hinge, and glued the aluminum trim into place.
And then it was finally time for a test spin of this restored Beogram 4002! I selected one of my favorite CTI label releases (CTI 7073), 'Crawl Space' by Art Farmer, which he recorded in 1977. Of course this album was cleaned ultrasonically on a CleanerVinyl ProXL setup before play! This shows the Beogram together with this lovely album:
A perfect combination! Stay tuned for an update on the photocell replacement. Once that has been accomplished this deck will be ready for its trip back to California.

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