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!