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

*************************************************Note Added in Proof:*********************************************

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 Precision Machined Solid Teak Frame

I recently received a lovely new CNC machined solid Teak plinth from Christian Hakansson, to be installed on the Beogram 4000 that I recently functionally restored.

Unfortunately, this Beogram had an original plinth that was damaged at the corners (please, watch out for door jambs when you carry your Beograms around!!...;-):

I removed the plinth:

If you do this at home, please, note that there is a 5th bolt under the keypad, i.e. the keypad needs to be removed before the plinth can be extracted. 

The deformed particle board under the veneer suggested that this plinth not only had damaged corners, but also had been in contact with too much moisture at some point in time:

The installation of a new plinth requires that the metal fixtures be removed from the old plinth to be transferred to the new one. I usually wrap the plinth in aluminum foil and then I put it into the oven for an hour at 200-250F. Once it comes out the metal parts can be separated with a suitable spatula or similar:

Once the parts are off, the residual contact cement

needs to be removed. I usually soak paper towel with isopropanol or goo gone and wrap the metal parts in it:

I put aluminum foil around it to prevent evaporation:

After 24 hrs the glue can be rubbed off with the drenched paper towels:

This shows one of the cleaned metal fixtures:

I use ultra thin 3M 300LSE adhesive tape for the installation. This makes the process much cleaner than with contact cement. The tape can be cut out with a razor blade to match the frame shape:

It is important to not cover the little spring tabs that are in the back of the frame:

Otherwise they can get glued to the wood and are not able to perform their duty (holding the plinth in place once it is pushed back) anymore.

Now comes the moment where the metal parts are glued to the wood. This is probably the most difficult task since one only has one try and the parts need to be placed precisely at the right level on the frame. This is greatly simplified by using the aluminum panels of the Beogram. They have the right thickness and can be used to align the metal parts with the frame.

It can be challenging to get the metal parts all the way into the corners since there is adhesive on both sides. I usually deal this issue by using some parchment or wax paper to prevent one side from sticking, while I push in the part all the way into the corner:

This shows one side glued while the other still has the paper in:

Sometimes the metal parts are not entirely conform with the frame in the corners. Many Beograms actually came with this issue 'factory installed'...;-). I sometimes use tongue-and-groove pliers to help seating the metal parts in the corners. Be careful not to damage the frame if you do this at home: 

This shows the new frame with installed metal parts:

And here a couple happy shots of the Beogram 4000 with the new frame installed. Beolovely!!:

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: Installation of a Brand New Beautiful Solid Oak Plinth! - Very Beolovely!!

Another Happy Day in the Beolover's life! Recently I received a shipment with two new Beogram plinths from Matt Spangler in Oregon, who is the owner of Vintage HiFi Nut. He specializes among other things in restoring/replacing wood cabinets of vintage HiFi. 

A while ago I sent him each a Beogram 4000 and a Beogram 4002 plinth. Both had been mashed up during shipping due to poor packaging. Unfortunately, this is a common issue since many people underestimate the raw forces in play during the handling of packages in sorting centers and on trucks etc...

Anyway, I received these two plinths back a few days ago. Today I had a look:

The top one is the 4002 type and the bottom one the 4000 type. Wile they look very similar, the metal frames are different in 4000s and 4002/4s due to the different size of the keypad clusters and aluminum plates. Here is a detail shot of the very well defined corners:

The top frame was made from solid Granadillo (aka 'Mexican Rosewood'), while the bottom frame was made from solid Oak. The original hardwoods that B&O used, Brazilian Rosewood and Teak are protected species these days due to over-harvesting, and so one has to use alternative hardwood types if hardwood looks are desired.

B&O did use oak in 'the day' on a smaller number of Beograms, i.e. an oak replacement can be considered 'original'. Personally, I think with wood cabinets one can have a bit of an open mind, and whatever looks great on these iconic vintage designs is great!

This is the sad look of the Beogram 4000 that I received recently:

I bought this Beogram 4000 from a seller in Germany. Unfortunately, despite pointing him to my packaging video, he did not believe in double-boxing and foam padding, and so the unit got mashed up a bit on one corner. The padding he used was less than an inch and so this was almost predictable.

While the right side only came unglued, the left was damaged beyond repair:

So when I received Matt's new frames, I decided to try out the solid oak 4000 frame on this unit. I removed the aluminum panels, platter and keypad to be able to remove the damaged plinth:

Then I installed the solid oak one that carries the 4000 metal frame. Here are a few impressions of the awesome look of this new plinth:

I absolutely love this fresh and happy oak look! A perfect complement to the bright aluminum plates. In my opinion it looks better than the original teak frame (oh, what heresy!!...;-). Matt really did a wonderful job with this cabinet! I cannot wait to install the Granadillo frame on a needy 4002.

This Beogram 4000 is on its way to a like-new look and performance! I will fully restore it and then it will be available to another B&O enthusiast! Stay tuned!