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: Exchanging the Plinth Panels

The Beogram 4000 that I am restoring right now came with a shaved off plinth corner (why can't people be more careful when they lug their Beograms around?? Just walk slowly and watch out for door jambs!...;-). This is how it came:

Since 4000 plinths are rare like the 4000 itself, most likely you will need to get the plinth wood panels from a 4002 or 4004. This means the metal fixtures on the plinth need to be exchanged, since they are slightly different due to the different keypad shapes (see here for more detail on the differences).

The first step is to remove the plinth, which is held by 5 screws to the metal enclosure. One of the screws is under the keypad, i.e. it needs to be taken out if you do this as a separate procedure.

Once the plinth is out the metal fixtures need to be removed. This is best done by 'baking' the plinth for ~30-45 min in an oven set to the 'warm' position, which usually yields about 80C. I usually wrap the plinth in aluminum foil to ensure a more homogeneous temperature distribution.

After the plinth was heated up, I took it out and removed the metal parts by jamming a spatula in-between. The heated old contact cement gives way fairy easily:

Take care to not damage the veneer while doing this.

The next step is the removal of the old glue from the fixtures

which is easily done by wrapping them into isopropyl alcohol drenched paper towel

followed by aluminum foil to prevent evaporation:

After letting the parts 'stew' for an hour, the glue can be wiped off with the drenched paper towel:

The glue on the wood panels needs to be left in place to not damage the veneer, but that is not a problem since it usually seems to be very thin and well distributed. I think the wood absorbed the glue when they applied it.

The next step is to assemble the panels of the replacement plinth from the 4002 or 4004, which of course also had to be liberated from its metal fixtures with the above approach.

I use Gorilla wood glue and some specially designed clamps that can hold the panels precisely in place:

After the glue fully cures (~24 hrs), the next step is to glue the metal fixtures back into the wood frame.

The first step is applying fresh contact cement to the metal parts

 and the wood panels:

I use small foam blocks for distributing the glue

Key is to make a thin homogeneous layer, and one does not have much time with modern contact cements. It is best to do it in separate steps for each side of the plinth.

After the cement is fully cured (~5 min) precise alignment is key during assembly. Otherwise the plinth will not be aligned properly with the aluminum panels of the Beogram.

Luckily one can use the Beogram aluminum panels themselves for the alignment process.

Place them on a flat surface and tape them down in an aligned way. On the outside I use a straight ruler. The aluminum panels have just the right thickness to 'lift' the metal parts to the correct position inside the wood frame:

When assembling the cement coated parts, it is crucial that they are aligned before they are pressed into place. This is difficult with a L-shape, since it needs to be pressed/moved in x- and y- direction at the same time. The trick is to insert a parchment or wax paper strip on one side of the L and then press the other into place:

Once one side is in place, slide the paper out and press the other side into the frame.

And that is the result:

One word of caution, when transferring plinths: They appear to come in two slightly different widths:

This caused an issue with this Beogram 4000, since the first time I did this process I used plinth panels that were the wider type, while the shaved off plinth was the narrower type. This caused the transferred plinth to not align properly with the enclosure, and one of the corners came unglued again due to the stress on the frame. So, the above pictures actually show the second time I did this for this Beogram. A hint if you have to remove metal fixtures that were just glued with modern contact cement: The modern stuff still gets soft when heated in the oven, but does not come off by soaking in isopropyl alcohol anymore. I think it is a different formulation for quicker drying with some probably 'happy making' organic solvents involved...;-). The trick is to replace the isopropyl with 'Goo Gone'...same drenching process with paper towel/aluminum foil.

Anyway, this Beogram 4000 plinth is fixed!

Beogram 4004 (5526): Final Adjustments and Test Drive with Art Farmer

The restoration of the Beogram 4004 (5526) that I have on my bench has come to an end. Today I did some more work on the hood and then the final adjustments, and then it was time for a test drive with Art Farmer ("Crawl Space" on the CTI label).

The hood needed some more attention after I polished it. The aluminum trim had come off on one side of it. I softened the old glue with a paper towel piece drenched in isopropanol:

After about 30 min the glue came off pretty easily:

I usually glue these side parts with 3M adhesive tape:

After cutting it to size with a razor blade

I removed the protective tape

This tape is ultra thin, i.e. can hardly be discerned. Then I clamped the pieces together:

And after a day of clamping the trim was attached again:

On to the adjustments:

After adjusting the sub-chassis and the platter, and the arms to be horizontally parallel to the enclosure, it was time to adjust the tone arm. First I did the arm lowering limit:

This makes sure the needle misses the ribs on the platter should the electronics malfunction and the arm be lowered onto an empty platter. Then I fixed the counter weight in place. The first step was to replace the flimsy locking washer on the bolt

with a M3 nut and a washer:

This allows locking the counter weight position in place by tightening the nut. Great for shipping a turntable. The next step was to adjust and calibrate the tracking force adjustment wheel:

Most B&O cartridges are specified for 1.2g tracking weight.

The final adjustment was the tracking feedback:

The light intensity trimmer on the Beolover LED light source makes the fine tuning very easy.

After cleaning the aluminum panels and the platter, it was finally time to play this Beogram!

I selected a recent acquisition to my collection, Art Farmer's "Crawl Space" Album, which I prepared for play with a thorough clean with the new CleanerVinyl EasyOne ultrasonic vinyl record cleaner.  Art Farmer recorded this album for the CTI label in 1977. This record has quickly become one of my favorites. Very smooth and melodic. Beautiful trumpet play...another awesome CTI release. What a beolovely sight and sound!:

I will play this Beogram a bit longer to make sure there are no intermittent issues, and then it will be time for it to return to its owner!

Beogram 4004 (5526): Tracking Sensor LED, Non-Working Carriage Switches, Final Adjustments and Test Drive with Eddie Henderson

The restoration of the Beogram 4004 (5526) that is on my bench is coming to an end. This post describes the final tasks of the project. After replacing the sensor arm bulb with an LED, I tested the carriage functionality and it behaved like the end switch and the turn off switch both did not work. It turned out that the wires that connect the switches to the main PCB had broken off from their solder points (white and grey wires):

I reconnected them (the grey wire needed to be extended a bit since it was pretty short after taking some insulation off for re-soldering):

After this repair everything seemed to work in terms of carriage motion.

The owner decided to also let me replace the bulb in the tracking sensor compartment with a LED assembly. I recommended this since this is also an essential light source, whose failure would disable the Beogram.

This shows the original tracking sensor light source in place:

I removed the bulb housing, which reveals the aperture that activates the sensor in the lower half of the assembly:

This shows the original bulb and the LED replacement in comparison:

The LED is in the same location like the filament of the bulb. This shows the LED assembly in place:

The blue trimmer allows fine tuning of the tracking sensor response, which makes it easier to adjust the system to spec. I also replaced the standard often rusty sheet metal screw that secures the aperture assembly in place with a M2 stainless socket head screw and a matching nut. This makes the initial coarse adjustment of the aperture position much easier.

Now it was time to adjust the platter height and the floating chassis horizontality. Then I moved on to the tonearm adjustments. An important item is adjusting the arm lowering limit. It needs to be set in a way that the needle 'misses' the ribs on the platter at the setdown points as an additional safeguard against needle damage should the record detection mechanism ever fail and the arm gets lowered onto the naked platter. This shows the adjustment result:

Then I moved on to the tracking weight. The first step is usually replacing the flimsy retaining clip on the counterweight screw with a M3 nut. This allows tightening the counter weight position down, which preserves the calibration over time and during shipping. This shows the original setup:

And with M3 nut:

Then it was time to calibrate the measured weight with the adjustment scale. I usually do it at 1.2g, since that is the weight at which most B&O cartridges track best. The weight scale on the adjustment wheel is notoriously imprecise, i.e. it is always best to confirm the weight with a digital gauge:

After this I adjusted the tracking feedback:

And then I tried to play a record...and all I got was a very loud hum from the speakers! Unbeolovely, entirely!

Hum usually means a broken connection in the grounding system between amplifier and turntable. It turned out that the shield connection in the DIN plug was disconnected:

Since the original DIN plugs cannot be opened up without destroying them, I needed to install a new plug:

The gold coated pins are a nice improvement in the signal path over the original corroded pins. This quenched the hum and the deck started sounding properly.

So it was time to listen to a nice record and enjoy this lovely 4004! I picked a recent addition to my collection, "Comin' Through" by Eddie Henderson. Of course this vinyl was cleaned with a CleanerVinyl Easy6 before I played it! Henderson recorded this album in 1977, and there are a few great funky tunes on it. My favorite is "Movin' On" on the first side. 

Beolovely! I will play this Beogram 4004 for a few more days and then it will be time for the return trip to its owner!