Beogram 4002 (5513): Installation of a Modern Universal Voltage Power Supply

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The Meanwell RS25-24 supply used in this post will need 500mA slow blow/time delay fuses installed in the black fuses box of the Beogram if it is to be used with 220-240V outlets. I used a 0-250V variac for testing the supply when I wrote the post below. Since a variac is typically ramped up from 0V to the desired voltage, the inrush current of the supply was lower during my testing than when the supply is directly plugged into a higher voltage outlet. So it worked fine at 240V with the standard 250mA fuses that are installed in the 110V DC motor Beogram types. But they blew when the Beogram was directly plugged into 240V. 500mA fuses seem to alleviate the issue. Live and learn!...;-)

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In recent months I received a few customer requests regarding fully restored Beogram 4002/4004 that I often have for sale. They wanted to know what it would take running US 110V models in Europe or Australia on 220V or 240V (unfortunately, most Beograms offered to me are 110V US models due to geographic constraints). My answer used to be: Get a small 50W 220V-to-110V transformer. Off course, the drawback with this approach is that there is an additional little box somewhere in the setup. Not very Beolovely!

So I set out to find a more elegant solution: The replacement of the internal transformer with a modern universal AC/DC power supply. These supplies are called 'universal' since they can take any grid voltage from 100V to 240V, i.e. they can be plugged in in any country around the globe. Another added benefit of such supplies is that they do not hum. The original transformers occasionally start making a 50/60Hz hum when the encasing resin gets old and shrinks a bit. When that happens the windings are not held firmly in place anymore and so they can start mechanically oscillating in the magnetic field generated by the 50/60Hz AC current. 

Voltage considerations: Modern off-the shelf supplies mostly put out 5, 12, 24, or 48V. The main power rail of the Beogram has a stabilized 21V. But the arm lowering solenoid is powered directly from the voltage coming out of the rectifier/main capacitor before the 21V regulator to give it a bit more voltage. This non-stabilized voltage is usually around 30V and depends on grid fluctuations since the transformer has a fixed conversion ratio, i.e. if the grid voltage goes down a bit, the voltage at the rectifier follows proportionally. This means they gave this setup a bit of 'headroom' so the Beogram would still work properly when everybody turns on their AC on a hot summer day. 

Another important factor for this project was that the footprint of the new supply would need to fit into the space of the transformer. 

With these constrains in mind I finally settled on the Meanwell RS25-24 supply as a promising candidate. Meanwell is an established supplier of power supplies. I have used them in the past for projects and also use them for my 3D printers. I think they have a high reliability.

Their RS25-24 supply is an enclosed type, i.e. is very safe to work with. It can supply 25W (the DC-motor Type 551x/552x Beograms are rated 15W, i.e. it has plenty of overhead for this task). The output voltage is 24V, but it is adjustable over a certain range, i.e. a higher voltage is possible. When I received it, this was the first thing I checked:

It turned out that the maximum voltage was 28V. This is a stabilized voltage, i.e. this will not change, regardless what comes out of the outlet in your wall. For a test, I connected the supply directly to the main reservoir capacitor of the Beogram (The Beogram was of course unplugged at this point!...;-) and pressed START. The Beogram happily came alive, found the LP setdown point and the solenoid solidly activated. It was hard to push back with my finger, very similar to using the original power supply. So it seemed the Meanwell supply was able to run the Beogram!

I started working on replacing the transformer. This shows transformer and fuse box still in place:

Fuse box and transformer are held down by two screws each:

I removed the screws and then I was able to lift both up:

The fuse box contains a dummy voltage selector that only serves as a vessel for routing the gray line cable to one side of the two fuses and the red/yellow wiring to the transformer after the fuses:

This shows the fuses-side of the assembly:

You can see how the wiring is soldered to the two fuse holders. I think they used two fuses since this design is a carry over from the real voltage selector used in earlier models, and for voltage selectors two fuses are needed to cover all the winding connection permutations properly (voltage selectors for transformers are a fascinating topic by itself, I could write a full blog post about it!...;-).

Mechanically the RS25 is pretty similar to the transformer

In fact, the mounting holes are identically spaced by 55 mm and both are holes for 3 mm bolts (albeit the Meanwell has threaded M3 holes, while the transformer uses self-tapping screws!). Maybe there is a standard for power supply mounting hole spacing depending on supply size! Unfortunately, this supply cannot be bolted in directly since it has a slightly different footprint that interferes with the power cable and the enclosure itself were the mounting holes used directly.

For this reason I designed a 3D printed adapter plate that allows placing the supply in the proper location while providing a 'channel' for the power cable to run under it and be out of the way:

The supply bolts on with two socket head M3x10 bolts:

I used a ~110mm long double stranded wire to make the connection from line-in to fuse box 

and cut the blue transformer output wiring at a suitable length so the other end of the wiring would fit perfectly to the output terminals of the supply:

I fitted two 3 mm solder lugs to the blue wires and secured them with some shrink tubing:

Here you can see the wires bolted to the supply terminals:

You may wonder at this point, why is the Beolover connecting wiring formerly conducting an AC voltage to the rectifier on the main PCB to the DC output of the new supply!? I could have of course done a clumsy soldered connection between the DC output of the supply and the output of the rectifier on the main PCB, since the rectifier is not necessary anymore for this setup. But why make something messy, if I can simply use the existing wiring harness which makes this a nice and clean install? A rectifier can naturally take DC, too. In fact it allows connecting the blue wires in either polarity to the supply since it will happily convert a negative voltage into a positive one, like it did it 50/60 times a second with the original AC input. The only slight drawback is that the current flows though two diodes in the rectifier, i.e. it will be lowered by about 2x 0.6V and the board only gets around 27V instead of 28V. But it seems 27V still works very solidly (see below), so this is not really a concern for this setup.

The next step was soldering the red/black line-in wiring to the fuse terminals. For this I stuck them through the holes that previously accommodated the red/yellow input wiring of the transformer

and then soldered the leads to the fuse terminals:

This shows everything placed for a preliminary fit:

I had to adjust the length of line-in wiring inside the enclosure since it now runs through that 'channel' in my adapter piece. This is easily done: Just pull out the cable gland by squeezing it with suitable pliers 

Here you see it pulled out:

And inserted back with the cable length adjusted:

Then I bolted everything in:

And tested whether the carriage would still have enough room to move completely beyond the end switch (ES) that turns it around when it sweeps an empty platter:

This experiment showed all good in the carriage movement department. I think I will move the Meanwell supply over to the left a couple mm more in my 'production' version of this setup. There is still a bit of room on the terminals side of the supply. Just in case...

An interesting item to look at after this conversion is the solenoid voltage behavior during engagement. This shows the voltage measured at the collector of 1IC4 (the pnp Darlington that drives the solenoid) with the original transformer setup:

This pretty much matches the schematic curve shown in the 5513 circuit diagram. When the solenoid activates the voltage starts out at ~30V and then caves to ~20V within ~20ms as the main capacitor depletes. Then the electronic limiting circuit kicks in and the voltage drops to ~2V for protecting the solenoid coil. 2V are apparently enough to keep the solenoid safely engaged against the return spring while the record is playing.

This shows the same measurement with the Meanwell supply installed:

The voltage starts out at about 26V and then also drops to 20V like in the original setup as current is drawn from the capacitor. In both cases the supplies are not able to fully provide the inrush current to the solenoid (~4 Amps), i.e. the main capacitor is essential for providing electrons for the brief moment while the solenoid engages. I think this is a very solid result for the RS-25 supply indicating that it is a good replacement for the original transformer setup.

In summary, I think this setup is ready for prime time and it can safely be implanted into single voltage DC motor Beograms to make them 'global players' (pun intended!...;-).

Note that this will not work for earlier AC motor models, since they require more power due to their wasteful (but great!...;-) synchronous AC platter motors. The AC motor Types (550x) are generally rated 50W, i.e. the RS25 series of supplies would not be powerful enough. Even though I am wondering if they might do the trick if the energy saving Beolover Efficient 22.8V Power Supply and Main Capacitors for Beogram 4002 (Types 550x) would be installed along with it.

Another interesting experiment for a lazy Sunday afternoon!...;-)

Beogram 4004: Repair of Transport Damage

A Beogram 4004 that I had restored in December of 2023 came back to my bench with some significant mechanical damage. After I removed the aluminum panels I found a strongly bent carriage spindle bearing bracket:

Some fairly brutal force must have whacked the deck on its left side to cause the carriage weight to bend the bearing bracket. This basically created so much friction that the carriage was not able to move again. An examination of the enclosure yielded that there is also some damage on the plinth. It seems it was hit by some object on the left side close to the corner where an indentation can be seen:

More scrutiny yielded that the off-switch had a dislocated return spring, which immediately explained why the deck would not shut down anymore:

I did my best to bend the bearing bracket back into shape and I restored the switch:

This essentially allowed the carriage to move again unobstructed and the deck shut properly down again. At this point the deck would still not track properly, however. I realized that the arms were also out of alignment. I restored their orthogonality and parallelism, and then adjusted the tracking feedback. This made the deck work again properly.

I will now play a few records on this deck to make sure I did not miss anything, and then it should be time to send it back to its owner in the UK.

New Replacement Keypad Plates for Beogram 4002 and 4004 are in the House!!

A happy day in Beolover world!!:

After about three years of time consuming and costly effort one of us (Beomazed) finally figured out how to manufacture faithful reproductions of the often worn keypads of Beogram 4002/4004/6000.

Finally, another milestone on the way to perfect cosmetic restorations achieved!...;-).

Here a couple impressions of one of the new keypads recently installed in a Beogram 6000:

The challenges were twofold:

1) First, a manufacturer had to be found who could make faithful reproductions of the original metal plates. A number of materials and processes were tried out until finally a perfect keypad plate emerged that had the proper springy feel and the perfect brushed look.

2) Then a coating material had to be found that would give the new metal plates the characteristic look of the original ones. This was pretty difficult due to the color and hue changes the original pads exhibit when observed under different viewing angles and in changing lighting situations. After many trials finally a coating was found that matched the original behavior well. While looking great, it is also an advanced material that is very durable.

It is pretty difficult to take pictures of finished metal surfaces that faithfully show the actual look observed directly.

Therefore, I removed the slightly worn keypad of my bench 4002 for taking some pictures in direct comparison under different light and camera angles. This direct comparison allows a better impression how close the new pads are to the original look.

These pictures were taken in diffused natural light:

And this one with a more harsh LED light coming in from the back on my work bench:

I think it is obvious that the new pads match the originals quite well.

Of course there are small differences as should be expected with any reproduction process. Also keep in mind that the original keypads probably looked slightly different when they were new. Most materials slowly change their optical properties as they age due to chemical and surface structure changes.

Stay tuned for updates. We will soon offer a restoration service for worn keypads.

New Beolover Carriage Position PCB for DC-Motor Beogram 4002/4004s (Types 551x and 552x)

I always found the repair and adjustment of the carriage position sensor on the PCB underneath the carriage somewhat tedious. The board and circuit are designed in a way that make a precise alignment of the LED, sensor and plexiglass ruler across the entire travel of the carriage necessary to ensure proper functioning. At the same time photosensor failures and mechanical failures of the sensor housing or the two switches on this board were sometimes difficult to fix, while broken off wires occasionally caused operational issues.

So I decided designing an improved board that would provide a reliable fix for all these issues at least in DC-motor Beogram 4002/4004s (Types 551x and 552x), where this board can be easily replaced. This shows the final design of the board:

The board features new SO and ES switches, as well as a modern monolithic IR photo-interrupter whose signal is cleaned up and shaped by an opamp in combination with a Schmitt trigger. It connects with a modern harness using a 2.54mm 8pin adapter to match the classic Molex jack on the main PCB. This connection should last much better than the original soldered wires.

The part is now available at the Beolover Store. I also gave this board a built in sensor test feature. Flip the switch to the right and an integrated LED will light up every time a black band on the ruler is properly identified by the sensor:

This shows the board installed:

My tests yielded a proper carriage position detection, while the SO and ES switch were in the correct location and performed perfectly. It seems that the modern photo interrupter due to its fixed alignment between LED and phototransistor is much more forgiving regarding the distance between ruler and photosensor. This makes the alignment between ruler and sensor across the entire translation range of the carriage much easier.

A good test for the proper functioning of the position sensor is whether it can read out the run out groove detection pattern at the end of the ruler. I measured the signal at the collector of TR17 while this section passed through the sensor:

A nice clean trace! All good in the carriage position detection department!

Beogram 4000/4002/4004: Test of New Custom Manufactured Beolover Carriage Motor

Sometimes carriage motors in Beogram 4000, 4002 and 4004 can be pretty noisy. Most likely their bearings are also in need of an oil infusion under vacuum, like the DC platter motors. Unfortunately, both the original Faulhaber and Maxon motors cannot be opened easily. So the remedy until now was a drop of oil on the shaft and hoping that this would do the trick for some time. After all these motors run much less than the platter motors.

But I always thought this was a less-than-Beolovely solution. Therefore, during the last couple years I tried out a variety of small motors with similar footprint but had to find out that all standard motors were way too noisy and vibration generating. Only after I sent one of the original motors to the supplier of the motors that I use in the Beolover SyncDrive for evaluation it became clear that the carriage motors used in the Beogram 400x are something special:

They are so called "coreless DC motors". Such motors have a rotor constructed as a hollow, self-supporting coil, often in a basket or honeycomb pattern, which eliminates the need for an iron core. This results in reduced mass, reduced eddy currents, lower inertia, and smoother torque/lower vibrations. The result is a motor that runs much more quietly and draws less current compared to normal motors with iron cores for the same performance (but that also has a significantly higher price - you get what you pay for!...;-). The quietness is crucial for driving the carriage since the slightest vibrations on the floating chassis can translate into sound audible in the speakers since they directly couple into the pickup. During my trials of standard motors the carriage drive was quite audible while listening to music at moderate volumes.

My supplier was able to design a modern coreless replacement that has a torque and voltage that is close to the original motors. I had a few samples manufactured and recently received them.

Here is a picture of the new Beolover carriage motor fitted with a custom pulley::

These motors are now available at the Beolover store.

The motor is easily mounted in the original motor enclosure using two EPDM rubber O-rings that help dampen any vibrations the motor may emit and also align it with the enclosure:

Since the new motor is a bit shorter than the original Maxon and Faulhaber motors, the leads can be fed though the cutout in the bottom of the enclosure:

This makes for a nice and clean installation:

It is a good idea to replace the original usually wobbly plastic pulley on the carriage spindle with a new precision machined Beolover aluminum pulley when exchanging the motor.

I performed some measurements that compare an original Maxon motor in one of my Beogram 4002s with the new motors. These oscilloscope traces show the voltage at the motor terminals while playing a record. The first curve corresponds to the original motor:

And the second one to the new Beolover motor:

The oscilloscope settings were the same for both measurements. We see that the new motor responds at a lower voltage, which corresponds to a smaller deflection of the tonearm necessary to get the motor to move. This is most likely a result of the lower friction inside the motor due to its fresh bearings that provide optimal lubrication. The consequence is that after implantation of the new motor the tracking feedback may need to be adjusted slightly to get the specified sensitivity. If a Beolover Tracking Sensor LED Light Source has been already installed in the tracking sensor, this can be achieved by simply reducing the light intensity of the LED slightly by adjusting the built in trimmer.

An important factor in motor replacements is the current draw under identical operational conditions. The H-bridge on the main board already struggles a bit with the current consumption of the original carriage motors, which is evident in the occasional need to replace the power transistors, especially those providing the current for the travel direction towards the home position (>>). So I definitely did not want replacements that would draw more current than the originals.

These are my measurement results for the two motors:

The only difference between the two columns is that the original motor was replaced with a new one. All other parameters like the <, > speed trimmers were kept the same.

It is clear that the new motors draw considerably less current in the same setting. Their performance however is very similar to the original motors as can be seen from the time it takes to complete a full platter sweep. This was done with an empty platter and measuring the time it takes between pressing Start and the moment the deck shuts off after the carriage came home again. The original motor did it in 18.0 seconds while the new motor was slightly faster at 17.5 sec. It should be noted that these absolute numbers will be somewhat different in every Beogram due to friction variations caused by adjustments and lubricants etc...But it is clear that the new motors will result in much less heat load in the H-bridge.

Another happy aspect of the new motors is that during these tests it became apparent that the new motors run noticeably quieter than the original ones. Which may have to do with their more modern design, but also with their fresh bearings and better lubrication.

In summary, it appears that the Beolover carriage motors are an easily installed cure for noisy original motors.

Beo4 Enabled Commander Remote Control: Seamless Integration of Beogram 4002 or 4004 with More Recent B&O Systems

A few months ago, Dirk, a fellow Beolover in Berlin, contacted me and suggested that it would be a nice thing being able controlling his Beogram 4004 with a Beo4 remote control. He has a Beosound 9000 in his living room, and wanted to integrate his Beogram in a way that it ideally would behave as a 'Beolinked' source.

I appreciated this idea and figured out how to modify the existing Beolover Commander remote. Basically, it needed a 455kHz capable IR receiver for communicating with a Beo4 and then I had to figure out how the Beo4 'ticks' in terms of codes it sends out in certain operational circumstances and rewrite the firmware.

Since the Beo4 is a fairly complex remote control with many modes, this was not trivial. But in the end I think I was able to arrive at a useful point, where the Commander equipped Beogram would pretty much behave as if it were connected to the Beosound via Beolink. 

I made a short video that demonstrates this system. The video contains footage that Dirk sent me. It shows how his Beogram interacts with his Beosound. He even figured out how to make a Beoremote One work with the Beo4 Commander! Very awesome! Enjoy:

The Beo4 Commander is available at the Beolover Store if you want to try this at home!..;-).

Beogram 4002/4004 (551x/552x): New Reservoir Capacitor Design

I thought it was time to redesign my main capacitor replacement for Beogram 4002 and 4004 (Types 551x and 552x) with DC platter motor.

This shows the new Beolover part (available at the Beolover Store):

It is built using 1000uF 105F type Rubicon Made in Japan capacitors. The assembly can replace both single capacitance and dual capacitance original capacitors. It has the rectifier for the second voltage rail (orange wires) built in.

This shows an original dual-capacitance setup:

It is different from the standard single capacitance setup in that it has two separate capacitors in a single can. They share a common negative connector (on the right end in the picture below). On the opposite side there are two positive terminals one for each capacitor. The capacitors have 4000uF and 1000uF values: 

The little round object bolted to the screw that holds the capacitor in place is a rectifier for the second (orange) power rail that is supported by the 1000uF capacitance. The two green wires are the AC inputs from the transformer and the orange and black wires are the DC output. The blue wires are the AC input to the rectifier that makes DC for the main PCB. That is the reason they terminte in the 4P plug that connects to the main PCB.

This shows the front of the capacitor with the orange wire and the regular white one that connects to the rectifier that is on the main PCB:

Here a detail shot of the rectifier:

The first step for installing the new Beolover main capacitor is to remove the original capacitor. The rectifier is not needed anymore, it is integrated on the Beolover main capacitor:

The next step is to solder the black and white wires to the respectively marked terminals. Then solder on the two green wires to the terminals marked 'green':

Then insert the base of the assembly into the 'compartments' of the enclosure bottom like so:

Then put the main capacitor board on top:

and then bolt it in with the screw that held the original cap in place:

The final step is to solder on the orange wire:

Usually it is just long enough to wrap it around one of the capacitors. This keeps it nicely organized.

And that is pretty much it. The main capacitor is now ready for duty! If the Beogram has the standard single capacitance 4000uF capacitor the installation sequence is the same, except that only the white and black wire need to be soldered to the capacitor terminals.