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 4000: Installation of a New Reed Relay

This is the third installment of my 'this Beogram keeps on giving' series about the Beogram 4000 from Australia that I have on my bench currently (in other words the Beolover is having some fun!..;-):

After fixing the tonearm wiring and the broken photocell in the sensor arm, this Beogram decided to give me a never experienced before new phenomenon:

After pressing OFF, the carriage returned home as it should, but after touching base, it decided to go back for an inch or so until it decided to finally come to rest. As if someone pressed ON again and then after a few milliseconds one of the < or > keys to bring the carriage to a premature stop before setting down on the record. Very strange! This was completely reproducible, i.e. happened every time I tried. Otherwise the deck seemed to perform normally.

After a bit of head scratching it occurred to me that maybe the 24V rail that controls the analog part of the control system did not shut down properly after the carriage triggered the off switch. I examined the reed relays that control the power in the Beogram 4000 and it became quickly clear that the one responsible for this 24V rail was stuck on closed.

The power supply setup in the Beogram 4000 can be a bit confusing, so a while ago I already made a schematic labeling some of the 'ingredients':

There are four reed relays (i.e. relays that are activated by a magnetic field generated by a surrounding coil to ensure galvanic separation of the circuits) that are controlled by two coils. These coils are the two big yellow items in the picture above. Each coil has two round passages into which the glass relay tubes are inserted. On either side the relays are connected with solder tabs that are inserted into the circuit board below and soldered to it on the backside. 

The upper coil relays control the 24V platter motor power and the power to the strobe light. Since the strobe light runs on about 90V that come from a dedicated secondary winding in the transformer this relay is fully insulated with shrink tubing.

The lower coil contains the 6V relay that controls the power to the digital control system inside the keypad cluster (basically the 'brain' of the 4000...;-), and the 24V relay that supplies power to the analog part of the control system (the 'muscle'...;-). 

This latter 24V relay is the one that was the root cause for the observed phenomenon. This was quickly confirmed with a multimeter, showing continuity across it even when the power plug was pulled.

Luckily there are replacements available. This shows a new Beolover Reed relay for Beogram 4000 Power Supply:

The relay exchange is slightly messy. This shows the original setup with the 24V relay still in place:

For removal of an old relay, it seems best to remove its solder tab on the left side first and then unsolder the other end of the relay from the solder tab on the right. This makes it easy to pull the relay out towards the left which is less obstructed. Be careful to not damage the very fine magnet wire that connects to the coils when you try this at home.

The first step is to remove the solder at the point where the relay connects to the tab with a solder sucker. Then the tab can be bend a bit away from the relay pin and then from the backside of the board the tab can be unsoldered and removed. The next step is to unsolder the other end of the relay and then it can be pulled out. Note that it is easy to damage the wire insulation of the red wires that are also attached to this tab. This shows the setup after removal of the relay tube:

Here a picture of the extracted original relay (top) together with the new one:

The new ones are slightly shorter but have longer pins. This makes installation relatively simple. The first step is to cut the right side pin to the proper length and then insert the relay followed by soldering it to the right tab. Then the left solder tab can be slid over the relay pin and pushed back into the PCB followed by soldering in place. The final step is soldering the relay pin to the tab and cutting the excess of the pin off. This shows the final result of the implantation:

After this procedure the Beogram performed again normally. On to finishing this project up!

Beogram 4000: An Interesting Tracking Issue and Installation of a Beolover Efficient 24V Power Supply and Main Capacitor Array

I recently received a Beogram 4000 back that I restored in February 2024 for a customer in Massachusetts due to an issue with the tracking system.

The phenomenon described was that the carriage occasionally would not track after the needle was lowered into the run in groove. I tried for some time unsuccessfully to reproduce this issue until it finally happened after I put a new record on the deck. It became clear to me at this point that it depended on the particular record played since the problem was fully reproducible with this particular record, i.e. happened every time I started the deck.

After a bit of head scratching I figured out that when facing a 'fast' run in groove, the arm would move so fast to the left, that the carriage motor was not able to keep up moving the carriage along before the tracking sensor aperture had already completely passed past the photo resistor opening in the sensor, in effect turning off the motor. The motor voltage is directly controlled by the resistance of the photo resistor and if it is dark the motor stops running.

The big question at this point was why this would happen with this particular Beogram 4000 and not with all the other ones I restored so far. 

I set out to measure the motor voltage with my oscilloscope. This trace shows the evolution of the motor voltage during regular play of a track on this Beogram 4000 as I received it:

What we see on this graph is that the motor voltage 'oscillates' and that there are larger jumps every few oscillations. It turns out that the oscillations correspond to the rotation of the platter: Note the 4s per unit time constant and that there are two oscillations per scale unit. It takes about 2s for a rotation at 33 RPM...

The voltage fluctuations are essentially a result of the eccentricity that most vinyls have to varying degree. The graph means that the carriage only weakly moves during ~6 or 7 rotations and then in one large burst after the voltage gets big enough for the motor to overcome stiction. Then the carriage drives forward until the arms are almost parallel and then the process starts again.

This suggested that the amount of light falling on the photoresistor was not enough to generate a high enough motor voltage through the H-bridge.

I decided to modify one of my standard Beolover Tracking Sensor LEDs to give the LED a bit more current to make it light up more:

After I installed the modified light source I re-calibrated the tracking feedback gain to start moving the carriage after about 3-4 rotations and measured again:

This time the curve looked like this and the carriage reacted speedily after hitting the run in groove of the record that caused the above issue. During play of the same track as above it gave me this trace on the oscilloscope. This shows that the carriage is now basically moving every rotation of the platter.

There are still a few variations between the peaks, which probably indicates a variation of the friction the motor encounters as the spindle rotates. Most spindles are not completely straight and so there is some change in friction during a rotation. It appears that each rotation of the spindle corresponds to maybe 4-5 turns of the platter. Of course this depends on the particular record since the groove density varies from record to record.

It seems this issue is fixed, but of course I am wondering why this particular Beogram 4000 needs a higher light intensity. It may be that the carriage motor itself is a bit different and turns less easily than others at a given voltage. Another possibility is that the photo resistors in the sensor are different, or from a different batch. The Beogram 4000 has two photo resistors in the tracking sensor that allow the carriage to actually track both forward and backward (this was discontinued in the later 4002 and 4004 models which only have one resistor for forward movement).

This unit seemed to track about the same in both directions when the arm was moved to the right or left manually, so I think it is not an issue with one of the resistors. If it were, I would expect that only one direction be affected. B&O has a history of making small circuit changes over the manufacturing run of a design. Maybe they simply used somewhat different resistors or there was variation between batches of them. Possibly the potentiometer for adjusting the voltage into the bulb that is normally found on the original configuration of the tracking sensor of the 4000 is an indicator that they already had this issue when they produced them, and someone calibrated the bulb intensity before Beograms were shipped out.

We may never know!...;-). Anyway, let's hope this tracking mechanism is fit for duty again!

While the unit was on my bench my customer decided to let me install one of my new efficient 24V power supply and main capacitors boards for Beogram 4000:

These boards elegantly replace the big reservoir and motor capacitor mess that is normally found in Beogram 4000s. It also updates the old-fashioned linear regulator based 24V power supply that causes a lot of power loss and heat emission in Beogram 4000s. This board will make any 4000 run more efficiently and the unit will get much less warm.

This Beogram of course already had my previous capacitor replacement kit implemented:

Out with the old

and in with the new! This shows the board bolted in. The solder pads are clearly labeled and in the right spots for easy connections:

This shows all the leads soldered to the board and the motor re-installed:

All good now with this Beogram 4000!

I will play it a bit more and then it will be time to send it back to my customer!

Beogram 4002 (Type 550x): New Main Capacitor Array with Integrated Efficient 22.8V Power Supply

Immediately after offering the new Beolover Efficient 24V Power Supply and Main Capacitors for Beogram 4000 component, I received inquiries about whether this part could also be used in AC platter motor Beogram 4002s (i.e. Types 550x).

The earlier AC-motor 4002s have a fairly similar setup when it comes to their main power supply. But there are minor differences: The rail voltage is only ~22.8V instead of 24V, and they do not splurge on a continuously powered standby mode like the Beogram 4000. But they also waste a similar amount of energy during operation due to the fact that the 45V transformer voltage is regulated down to the specified 22.8V with a Zener stabilized power transistor. This results in a nearly 50% energy loss in the 22.8V rail in the transistor.

In my design for the Beogram 4000 I replaced this setup with a modern buck converter-based design that has a DC-DC conversion efficiency in the 90-95% range. This causes the Beogram 4000 to run much cooler due to the reduced heat load. I provided a basic analysis and explanation of this setup in my original post about this design.

While the voltage difference is not really an issue, unfortunately, the different turn-on method in the 4002s without stand-by prevents the direct use of the Beogram 4000 board in the 4002s. Therefore, I designed a dedicated board for 4002s that also directly replaces the main capacitors and the voltage regulator setup. This is how the new board looks (it is available for purchase at the Beolover Store):

The many round capacitors are high-quality 105C rated Panasonic electrolytic capacitor arrays that provide the new power supply with appropriate reservoirs and couple the motor to the Wien oscillator amplifier. The row of small 'boxes' on the left is an array of Samsung X7R type ceramic capacitors that add up to the 150uF of the non-polar original electrolytic motor phase capacitor. Ceramic capacitors are much better for this application since they are inherently non-polar and they can take AC current much more easily than electrolytic capacitors. The circuit on the far end of the board is the buck converter based 22.8V power supply.

It replaces is this original setup:

The two larger capacitors on the right (0C1/2) are the in parallel connected reservoirs for feeding the voltage regulator whose transistor (0TR1) is bolted directly to the chassis right of the motor. The reason that this transistor is not on the main PCB is its significant heat dissipation that needs to be sinked efficiently. A significant part of the energy going into the Beogram is leaving it as heat at this front corner. That is the main reason that this area gets pretty hot after playing a couple records. Motor and transistor pretty much divide maybe 40% of the total heat load of the deck between them. The rest is mostly dissipated from the transformer, the solenoid (when the arm is down), the Zener that controls the regulating transistor, the incandescent light bulbs and the electronics.

The other two capacitor cans are to couple power into the motor (0C3) and to shift the motor phase by about 90% for the second winding (0C4).

This is a snippet from the circuit diagram showing the setup of the original power supply:

The buck converter that is integrated on the board basically replaces the 0TR1 transistor eliminating most of its power dissipation.

Replacing this setup with the new Beolover board is straight forward. Simply remove the capacitors and then unsolder all the wires from them and the transistor:

The transistor can/should be left in place.

Then solder the wires that were connected to the transistor to the respectively labeled pads at the bottom end of the board:

Then connect the four wires from the motor according to their color:

Here a shot from a bit further away:

Then solder the red and black wires from the rectifier:

A detail photo:

Next are the wires that go towards the PCBs: The green wire goes to the pad next to the motor wires, and the two orange and black wires to the pads on the right of the rectifier wires:

And that is it: This shows the board fully connected and bolted in:

And with the main board replaced:

Beolovely!

Like for the Beogram 4000 setup, I also measured the temperatures and currents before and after. This is what I got (33RPM, 13.2V motor voltage, arm up and carriage at rest):

Similar to the results for the Beogram 4000, a significant drop in temperatures occurred: The motor temperature dropped from 47C to 38.4C, while the temperature at the transformer went down from 38C to 34.8C. As a consequence the deck does not feel unusually warm anymore to the touch.