Beogram 4000: Final Adjustments, Some Odds and Ends and a Test Drive with Cal Tjader

After exchanging the black painted plinth with a teak plinth from a Beogram 4002, it was time to do the final adjustments and give this beautiful Beogram 4000 a first test drive. After adjusting the platter height, tilt and alignment with the surrounding aluminum panels, I adjusted the arm lowering limit to ensure that the needle will miss the black ribs on the platter should there ever be a malfunction in the platter detection mechanism. The limit needs to be adjusted that the needle misses the lower parts of the ribs by about 1 mm:

The next step was to adjust the tracking sensor feedback that the arm would track parallel to the sensor arm:

Then came the motor waveform adjustment. Essentially, the trimmers need to be adjusted until a nice sinusoidal is achieved at the highest possible amplitude. An oscilloscope is helpful, but in absence of one it is possible to adjust the motor simply by listening to it. Increase the amplitude until it starts getting noisy, and then reduce it until the noise goes away. This is the measured waveform:

While I still had it open, I also installed a grounding switch that allows connecting signal and system grounds. This can be helpful for hum reduction, especially if RCA cables are used like in this Beogram (RCA does not carry the system ground, that is why there is usually a separate wire to connect the system grounds of amplifier and turntable when RCAs are fitted). This is how the output terminals looked like before implantation of the switch:

And after installing the switch:

Then I installed a nut on the screw that holds the counter weight of the arm in place. Originally, this screw is only held in place with a flimsy retaining washer allowing it to move a bit:

I took the retaining washer out and replaced it with a M3 nut and a washer:

This allows fixing the calibration in place in a more permanent way, which is a necessity if it is to survive the shipping process intact. Now it was time to calibrate the tracking weight:

This is done best with a digital gauge since they are very accurate and do not cost much money anymore. One last thing: One of the mounting bolts for the hood had a 'custom fashioned' spring that did not work very well. I replaced it with a new one to ensure trouble free hood installation:

And then it was finally time to give this lovely Beogram 4000 its first post-restoration spin!

I selected a recently obtained record by Cal Tjader from 1971, simply called "Tjader". His output from the 70s usually earns less raving reviews than what he did earlier, but I really like this record. Especially the tune "What Are You Doing The Rest Of Your Life" (one of my big questions, too!...;-) is a very nice and smooth tune. Here is an impression of Cal together with the Beogram:

A lovely combination! I will now play this Beogram a bit longer and then it will be time for it to travel back to Germany!

Beogram 4000: Exchange of Black Painted Plinth with a Teak Plinth from a Beogram 4002

The Beogram 4000 that I am restoring right now came with a black painted plinth. Not sure why some people have the need to mess with a piece of iconic industrial design, but I guess "before you criticize a man, walk a mile in his shoes" (Steve Martin - the quote actually goes on: "That way, when you do criticize him, you'll be a mile away and have his shoes.'...an important point if you live in a country that has more guns than people...;-).

Anyway, here is a picture of the sad state of affairs:

As usual this plinth also had cracked guidance washers:

I removed the plinth. For this one has to remove the keypad since one of the bolts that hold it down is underneath.

Unfortunately, it is not possible to just take a plinth from a 4002 and bolt it into the 4000. Due to the slightly different sizes of 4000 keypad and the small aluminum panel that sits behind it, the metal fixtures that are glued to the plinth on the right side are different. You can see this here:

The top fixture is from the 4000, the bottom from the 4002. At the front of the plinth another small difference can be noted:

The tabs that hold the keypad down are a bit wider spaced in the 4000.

This means that the fixtures need to be exchanged. Removal is pretty easy since the glue gives when heated to moderate temperatures. I resorted to wrapping the plinths in aluminum foil and 'baking' them on the lowest setting in our oven (~85C) for half an hour. After taking them out, it was straight forward to remove the metal fixtures on both with a paint scraper that is pressed in-between the wood and the metal and then moved along until the parts are separated. The glue can be removed with Goo-B-Gone (thanks for this tip, Sonavor!).

One the parts are separated the most difficult part of the procedure begins: Butting them back together in a precise and straight way. This is critical, otherwise the plinth will not sit straight and of course that would be un-Beolovely!

In the past I used industrial strength adhesive tape for reattaching partially delaminated fixtures from plinths, and so this was my goto here, too. I put strips on the wood and trimmed them with a razor blade to match the footprint of the wood parts:

The key to attaching the fixture to the wood is to align it perfectly with the milled out groove that is in the lower part of the plinth. It turns out that the aluminum panels of the Beograms have exactly the same height as this groove, and so can be used as a 'natural' guide for reassembling the plinth!

I used the small aluminum panel of the Beogram and borrowed one from one of my 4002s to cover the entire right side of the plinth. Then I removed the tape backing on the front (and left the backing on on the side that no gluing wold occur while I aligned the fixture at the front) and pressed it in:

The Aluminum panels kept the fixture at exactly the same height front and back, ensuring a horizontal alignment.

Then I removed the tape backing from the strips on the side and pressed the fixture in:

Then I clamped everything together and let it sit for a while to ensure that the bond was solid:

Then it was time to bolt the plinth into the 4000. For this I used new 3D printed guidance washers:

They are available via the Beolover Shapeways store if you need some.

It is a good idea to get one manufactured in black to be mounted in the front center spot. This washer can be seen through the crack between the plinth and the aluminum panel if it is white.

This shows two of them installed:

Below the keypad -

and center front:

When I took out the original plinth, the mirror came off from the keypad cluster:

I am glad this happened so I had a chance to glue it back on in a lasting way with a couple dabs of epoxy:

Without this mirror in place it is impossible to see the strobe markings underneath the platter that are illuminated by the wonderful fluorescent orange bulb that is run at the AC grid frequency.

Allright, here is an impression of the Beogram with the new plinth on!

Beolovely! This looks so much better than the 'black ops' version! All that is left are a few final adjustments, and then it will be time for a first spin! I am looking forward to that! Playing a 4000 for the first time is always a special moment!

Beogram 4000: Replacement of the Sensor Arm Bulb with a LED Assembly

After replacing the cracked MMC cartridge mount in the Beogram 4000 that I am restoring right now, it was time to exchange the last remaining incandescent light bulb with a LED based assembly. This shows the bulb compartment extracted from the sensor arm:

This shows the wiring on the bottom side of the small PCB:

The LED assembly is based on a flexPCB circuit that imitates the power profile of a light bulb to not confuse the control electronics of the Beogram (which checks whether the bulb is functioning or not).

I extracted the bulb. This shows the bulb in comparison with the folded flexPCB based drop-in ready LED assembly 

This assembly is available to other B&O enthusiasts. If you are interested, send me an email of use the contact form on the right. This shows the LED assembly installed:

And in action:

The small 3D printed red wedge on top of the PCB ensures that the LED is in the right location to project its light properly through the lens in the bottom of the bulb compartment.

Beogram 4000: Replacement of a Cracked Cartridge Mount with a 3D Printed Assembly

Like so many Beogram 4000s, the one I am working on right now had a cracked MMC cartridge mount. In the 4000 this part was made from a more brittle plastic than in the later 4002s, and it seems this material is not aging well. This is how this issue manifests itself:

The first step of this repair procedure is to take the arm out that the original part can be extracted. For this the screw in the back needs to be removed, and then the arm can be pulled out:

after pulling it forward a bit the part that holds the excenter down can be removed, revealing the excenter and the spring that pushes it down:

Pulling the arm further releases a spring that holds the wiring in place:

The the arm comes off and one can see the board where the wires to the cartridge mount are soldered on:

The next step was to unsolder the wires. Two of them are soldered to the bottom side of the small board:

These can be unsoldered using a mirror and carefully operating the soldering iron to get underneath from the side. After unsoldering the wires it was time to 'cook' the arm for a while to soften the glue that holds the MMC mount in place:

This one needed to be heated for an hour or so until I was able to finally push the cartridge out with a metal rod that fits into the square arm profile:

Unfortunately, this 'pushing out procedure' often results in damaged wires since there is no way to keep them out of the way while pushing the mount out from the back. In this case I had to replace two of them...this shows the 3D printed replacement part with the transferred wires soldered on:

The next step is to install the mount together with the original bottom part:

I usually glue the parts back into the arm with white wood glue (Alene's, but any other will do, too). When doing this, care needs to be taken when the mount assembly is pushed into the arm that it is inserted precisely at a depth that allows to mount the cartridge snugly. This is best done by putting a cartridge on and then pushing the mount in with the cartridge:

After letting the glue harden for 24 hrs, the cartridge can be removed:

Now the arm can be installed again:

And bolted to the carriage:

Allright! On to replacing the sensor arm light bulb with an LED assembly...

Beogram 4000: Restoration of the AC Motor and Replacement of the Reservoir and Motor Capacitors

After restoring the PCBs of the Beogram 4000 that is currently on my bench it was time to look after the reservoir and motor capacitors, and the AC motor itself. This shows the capacitor and motor section of the deck in original condition: 

I started removing the old cans and found that the big ones had started leaking:

So it was definitely high time to get this done. This shows the capacitor bay after removing them:

I also removed the motor (this was a good moment since its leads were already unsoldered from the capacitors):

The motor is held together by threaded rivets. If one wants to open the motor to re-lubricate the bearings, these rivets need to be drilled out. This is how the motor looked like after returning from my drill press:

I opened it up

A very simple yet elegant construction! Made in Switzerland...those were the days...;-).

This is a close up of the rotor with everything that sticks on the shaft:

I immersed the two halves of the motor housing with the bearings in oil (it seems there is no obvious way to get the bearings out without doing major damage) and pulled a vacuum to draw oil into the bearings.

I have actually at this point no evidence that these bearings are indeed Oilite bearings. It seems no significant bubbles form after the vacuum is up. But the treatment has so far permanently cured all motors that were knocking, so I am continuing doing it....

While the bearings were in the oil I installed my capacitor replacement assembly:

It consists of a 3D printed plastic shell that holds the new capacitors in place, and that fits into the mounting strap of the original capacitor assembly:

The motor was reinstalled using two 3D printed 'nut arresters' that are used to replace the drilled out threaded rivets, that allowed to adjust the tilt of the motor relative to the platter axis (this allows to adjust the height at which the belt sits on the platter):

These plastic parts hold the M3 nuts in place that one can adjust the tilt screws agains the motor housing:

I also usually replace the original slotted adjustment screws with modern stainless hex socket head bolts. They make the tilt adjustment so much more straight forward when the platter is installed since one can use a ball end hex screwdriver at an angle turning them while the platter is rotating.

Unfortunately, in the meantime I had to realize that the MMC cartridge mount of this Beogram has the (frequently found) cracked MMC cartridge mount, so the next step is to replace it with one of my (you guessed it!...;-) 3D printed replacements.