Beogram 4002 (5513): Replacement of a Dead Transformer with a Modern Universal Power Supply

****Note added in proof: This solution will not work in earlier AC-motor Beograms (Types 550x). The Meanwell power supply used in this post is not powerful enough for those. There is now a dedicated solution available for the earlier Beograms. Please, see here.****

I am making good progress with the Beogram 4002 (Type 5513) from Louisiana. The unit had a short circuited transformer that needed replacement. During my initial inspection of the unit I found blown fuses and that some grey slime had leaked out from the transformer.

I decided to install a Meanwell RS-25-24 universal power supply like I did it recently with a couple of Beograms that I sent to the UK and Australia. Such modern supplies have a few advantages over the original transformers. They run on any input voltage between 100 and 240V and are short circuit protected. They also do not hum much, unlike some of the original transformers that often produce a noticeable 50/60 Hz hum when they are plugged in.

This shows the final result of my efforts:

The Beolover Transformer Replacement Kit for Beogram 4002 and 4004 (Types 551x/552x) is shown ere:

The Meanwell supply is shown flipped over with the adapter plate facing up. The plate allows the supply to be bolted to the same bolt holes that are used to hold the transformer in place. 

The wire harness connects the line-input of the supply to the fuses box. The additional solder lugs are used to connect the blue or blue/green wiring to the Beogram circuit to the Meanwell 24V output. The two screws are used to bolt the supply in place.

The provided 500mA fuses need to be installed in the fuses box of the Beogram. This ensures that the inrush current of the new supply does not overwhelm the fuses. The original 250mA fuses are not strong enough if the supply is plugged into 220/240 outlets.

Let's discuss the installation process:

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Safety first: Potentially lethal voltages can be present during the installation of this part. Unplug your Beogram before installation. Ensure that the terminal cover of the universal power supply and the fuse box cover are in place before powering the unit up after installation.

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This shows the primary wiring of the original transformer. Some cataclysmic event caused grey slime to emanate from the wiring orifice:

I removed the screws that fixed the transformer and the fuses box to the enclosure bottom. This released both components:

I first unsoldered the primary wires of the transformer from the fuse box terminals (be careful to not melt the black fuse box housing with the solder tip). Then I cut off the green and blue secondary wiring at the transformer housing. Next I installed 3 mm solder lugs on the secondary wires so they can be bolted to the output terminals of the new supply:

Make sure that the solder lugs connect to one green and one blue wire each. Both green and blue wires connect to rectifiers, i.e. their polarity is not important. Note that there are Beograms that have only the blue wires. In this case simply connect one lug to each of the blue wire ends.

The next step was soldering the grey wires to the fuse box terminals:

This is how it looks from the bottom side of the fuse box:

Both of the in and out wiring of the box need to be routed thought the 'exit channel' of the box:

Then the bottom cover of the fuse box can be stuck back on:

The next step is bolting the fuse box back to the enclosure:

Now it is time to connect the power supply terminals. The first step is removing the bolts from the two terminals on the left and the two on the right:

Then the wiring can be bolted to the terminals with the solder lugs:

The line-in wiring goes to the terminals labeled L and N.  and the gree/blue wires to the -V and +V labeled ones. The polarity of the wires is not important. Note that the ground connector in the center of the power supply does not need to be connected. The Beogram is a floating design based on galvanic separation via the power supply. 

Important: Make sure that the white trimmer potentiometer next to the terminals is turned all the way clockwise. This increases the output voltage to about 27-28V, which is beneficial for the operation of the arm lowering solenoid. In case you are worried about the performance of these modern supplies with regard to driving the solenoid, please, see here for some measurements that I did when I developed this upgrade.

Once the terminals are connected the new supply can be bolted in. The two small holes in the adapter plate fit to the original mounting holes of the transformer:

Just hold the new supply in place and put in the supplied screws from the bottom:

Then tighten them:

This shows the bolted in supply. Make sure the terminals cover is in place before plugging in the beogram!

This photo shows how the line input wire is routed from the cable gland at the enclosure orifice around the adapter plate to the fuses box. Also note how the green/blue wires go around the floating chassis and transport lock assembly towards the Beogram circuit board and Beolover reservoir capacitor assembly.

After the installation I made sure the terminals of the new supply were covered by the supplied plexiglass cover and that the cover was back in place on the fuses box. Then I plugged the Beogram in and pressed START. The carriage started moving and the arm dropped at the LP set down point! All good again in the power supply department of this Beogram! 

Beogram 4004 (5526): Installation of A New Output Cable

After replacing the light bulb in the sensor arm with an LED assembly it was time to look into the RCA plug 'conversion' of this Beogram 4004 (5526). This shows the output cable in the condition when I received this Beogram:

Not a very inspiring sight. The blue and yellow leads are the Beolink signal lines that allow controlling the 4004 via a Beomaster 2400. We decided to return this 4004 to its original DIN7 output scheme. Originally the 4004 came with a convertible male DIN7 plug, which can be turned into a standard DIN5 by unscrewing the two pins that are extra in the DIN7 format. This shows a plug as seen on a 4004 I restored a few years ago:

The two outer pins were removed so that the plug essentially acted like a standard DIN5 phono output. Unfortunately, such DIN7 plugs are not available anymore. A solution I came up with is to install female DIN7 plug that has all the signals on it. If extended with a DIN7 cable it turns into a DIN7 male output that will properly work with a Beomaster 2400. Extend it with a DIN5 or a DIN5-to-RCA adapter and a standard non-B&O phono output is achieved.

This shows the female DIN7 plug during the installation:

Note that the leads need to be soldered in a mirrored pattern compared to that applied for a male DIN7 plug, since male-male DIN5 and DIN5-RCA jumper cables mirror the leads for symmetry reasons.

This shows the DIN7 connected to a DIN5-to-RCA jumper cable:

The system ground connection is on a separate wire (not visible on this photo) that it can be connected to the GND terminal of the RCA input amplifier.

Beogram 4000: Upgrade of Signal Path with New DIN5 Plug and a Grounding Switch

As usual the original DIN5 plug on the Beogram 4000 that I am currently restoring was badly oxidized. This shows the original plug:

I replaced it with a new all-metal plug that has gold coated terminals:

Another useful upgrade of the signal output of any Beogram is the installation of a switch that allows connecting signal and system grounds. This is a useful feature if the Beogram is ever to be used with a DIN5 to RCA adapter. Since RCA cables do not carry the system ground, connecting it to the signal ground on the Beogram often eliminates humming. This shows the output terminal assembly of the Beogram 4000 in its original condition:

This open layout makes it very convenient to add a switch:

The shown switch position connects the two ground. Flipping the switch would open the connection.

Beogram 4002 (5523): Replacement of Corroded RCA Plugs

The Beogram 4002 (5523) that I am restoring right now was outfitted with RCA plugs and a grounding wire instead of the standard DIN 5 connector. As usual the plugs and the grounding terminal were grimy and corroded:

I replaced the RCA with all-metal gold plated plugs and I installed a new grounding terminal:

For some reason these nice compact RCA plugs do not come with a color coding, so a while back when I started using them in my restorations I designed 3D printed inserts that close off the back of the plugs and give them a distinguishing mark for the left and right channels:

On to the final adjustments and a test drive of this lovely Beogram!

Beogram 4004 (5526): Replacement of Convertible DIN7 Plug with DIN7 Socket and an RCA Adapter Cable

Any restoration of a Beogram should include the replacement of the DIN connector to ensure a low impedance signal path on the way to the amplifier. In the case of a Beogram 4004, the DIN connector is a convertible male DIN 7 plug, where the two additional pins can be unscrewed from small sockets. These two pins would carry the remote control signals from a Beomaster 2400, which is designed to control the 'start' and 'stop' operations of the Beogram 4004. An early form of Beolink, so to speak. But of course, if one does not connect to a 2400, these pins are not needed, hence the convertibility. This shows the plug with the empty two sockets at the ends of the 5 pin half-circle:

This type of plug is no longer available, and so I resorted to replacing it with a DIN 7 female socket, which then connects to a jumper cable with the desired number of pins or RCA termination. In essence this approach converts the Beogram 4004 output scheme to that found in the later Beogram 800x models, who have a DIN 7 socket mounted in the back of their enclosures. That way one can connect with both DIN 5 and DIN 7 jumper cables to a non-B&O or B&O amplifier.

Even cable mount DIN 7 sockets are difficult to find these days, but Steve at soundsheavenly.com can provide them. Here are a couple impressions: This shows the socket soldered on:

and with its shield in place:

And finally with a DIN 5 to RCA adapter cable:

Beogram 4004: Replacement of Convertible DIN 7 Plug with a Female Socket and Adapter Cables

While enjoying the Beogram 4004 that I recently restored I was looking for an adequate modern replacement for its convertible DIN 7 plug. This plug is a special design that does not seem to be made anymore. Here is a picture of its business end:

The picture shows the plug in its DIN5 configuration, i.e. it can now connect with any standard DIN5 amplifier input. The two (threaded) orifices above the pins can hold two more pins, which can be bolted in if the Beogram is to be connected to a Beomaster 2400 to take advantage of its remote control, which can be used to start/stop the Beogram. In essence these two additional pins carry the remote control signals for the Beogram. But, of course, since this is a male plug, the pins have to be removable if the Beogram is to be used in a standard DIN 5 setting.

Sadly, these plugs are nowhere to be found these days, and so, if a new plug is desired, another approach needs to be found to preserve the above 'convertibility'. My solution was to replace the plug with a female DIN 7 socket. That way DIN5 (or DIN5-to-RCA) jumper cables can be used for non-B&O set-ups and DIN7 jumpers can be used to connect to B&O setups. In essence, this modification gives the Beogram 4004 the same connectivity design like the later Beogram 800x, which have a panel mount DIN7 socket in their back panel to receive a suitable jumper cable.

It was pretty difficult to find a decent female cable mount DIN7 socket, but finally Steve at soundsheavenly.com saved the day by providing me with a few DIN7 Deltron sockets for cable mounting.

Here are a few impressions: This shows the socket installed. The red and white leads are the signals and the yellow and blue leads carry the remote control.

It is important to note that the signal leads on a female sockets need to be soldered to the other side of the connectors since male and female plugs have mirrored pin assignments to properly maintain the signal chain through the connections. This shows the fully assembled socket:

This is how it looks with a DIN5 jumper cable (also provided by Steve) plugged in:

This Beogram 4004 is finally ready to be shipped back to its owner!

Beogram 4000: A New DIN 5 Plug and Installation of a Grounding Switch

The Beogram 4000 that I am restoring right now had a badly corroded and poorly installed DIN 5 plug. Obviously not the original plug. Here are a couple pictures of the sorry state of this plug:

I think the dangling black lead may have been an attempt to reduce some humming issues (no surprise, considering the way this plug was installed...;-). Besides this strange construction, one of the signal leads was also disconnected due to a sad soldering job. 

I cut off the plug and prepared the leads for the new plug:

This picture shows the advantage of DIN connections over RCA: The entire cable and connectors are double shielded. Each lead is shielded by the signal ground lead and then there is an outer shield that connects the enclosures of amplifier and turntable. That way the shielding is complete, which gives the best defense against EMI. RCA usually only have a single shield via the signal ground. That is why there is usually a separate wire that connects the amplifier and turntable system/enclosure grounds.

Then I soldered it on:

And this is how it looks with the shield on:

Beogolden I'd say!

The final step of refurbishing the signal path was to install a switch that allows connecting signal and system grounds. This is a convenient features if there is a hum when connecting to RCA inputs via an adapter.

Switch to the left (as shown) and the grounds are connected. Switch to the right and the grounds are disconnected as in the original configuration. 

Beogram 6000 (5512): Replacement of a Corroded DIN5 Plug with a New Gold Plated Unit

Practically all Beogram 4002/4 and 6000 need their DIN5 plugs replaced due to various levels of  corrosion on the contacts, which were not gold plated back in the 1970s. This Beogram 6000 (5512) is a 'beautiful' example:

and with the shield removed:

I cut the rusty plug off and installed a new gold plated all metal plug:

and with the shield on:

Beolovely! The CD-4 preamp board is next!

Beogram 4000: Replacement of Corroded DIN5 Plug and Installation of a Grounding Switch

After rebuilding the control cluster the next step of my current Beogram 4000 restoration was to replace the original corroded DIN 5 plug with a modern gold plated all-metal plug, and to install a switch that allows connecting system and signal grounds in case there is a ground loop causing a hum in connection with the amplifier. This shows the rusty original plug:

And here the replacement:

Pretty! On to the grounding switch. This shows the terminals where the DIN cable is connected to the internal cartridge wiring:

This is the perfect spot to install the switch:

This switch allows to toggle between the B&O-original setup, where signal and system grounds are kept separate, and a configuration where both grounds are connected. B&O actually adopted this configuration in later 4002 and the 4004 Beograms. My experience is that if there is a hum, this connection in most cases suppresses it.