Beogram 4000: Hood Restoration - Polishing and Exchange of the Hinge

The Beogram 4000 that I completed recently still needed its hood restored. Of the two hoods I received, one had a crack up front at the left corner, while the other had a decent plexiglass body, but the hinge showed corrosion blooming under the black paint:

This is a frequent issue with Beogram 4000 hinges, and one can fix it by sanding the hinge down and then repainting it with black matte spray paint. But the better solution is to find a hinge that does not have this issue, since spray paint is never perfect. Luckily, the cracked hood had a near perfect hinge, and so I decided to exchange them.

Taking the hinge out is not difficult, but one has to get under the easily damaged aluminum  strip that graces the hoods in the back. This can be done by carefully inserting a razor blade between the plexiglass and the strip:

One needs to be careful to not damage the plexiglass around the strip or the strip itself. They easily break off at the bend. So it is best to not bend them out too much. This is enough:

It is important that it also comes off a bit at the bottom, which usually happens due to the age of the glue - if it does not: It may be best to heat the hood to ~70C in the oven and then carefully pushing the strip down at the bottom. The heat softens the glue making it come off much more easily. But let it get too hot, and the plexiglass starts deforming, so it is a bit of a scary thing to do. Luckily in this case the strip came off fairly easily without too much convincing necessary, so I did not have to go to the oven treatment. Once the strip is off, just remove the two screws on both sides and the hinge comes off. The replacement is easily bolted in and then the remaining task is to glue the aluminum strip back on. 

In the past I used double sided tape, but I had to realize that in some cases the strips lifted off again after a few months. Pretty un-beolovely! Therefore, this time I decided to try out contact cement, which, I think they also used initially when they made these hoods.

The first step is to remove the old glue, which can be softened by placing paper towel wads drenched with isopropyl alcohol into the gap and let it sit for ~30 min:

After this treatment, the glue can be scraped off with a razor blade:

Now it was time to apply a thin layer of contact cement to both sides with a tooth pick. I use this (Amazon):

It is important to not apply too much cement, and also stay ~1mm away from the front edge of the strip, since some glue can be squeezed out there when the parts are pressed together. 

After the cement is fully dry (~15 min) the strip can be pressed into place. Since the strength of contact cement bonds strongly depends on the force and duration applied when pressing the parts together, I developed a set of clamps specially designed for the task (it is difficult to just use carpenter clamps or similar due to the irregular shape of the hinge mechanism):

I pressed the strips back into place by hand and then applied the clamps:

I let everything sit for a day, and then removed the clamps:

Nice how precisely the strip conforms around the corners! Beolovely!

After this it was time to polish the hood, since it was pretty scratched on top:

I started out with sanding it with a 320 grit until all the scratches were gone, and then I polished it back up to translucency in 10 steps with ever finer grit and finally with polishing compounds. A nice 2 hrs workout in the garage, and then the hood looked pretty nice again:

The final touch was to install new rubber bumpers for that satisfying 'plonk' when closing the hood. The original ones are usually gone at this point in time since the rubber degrades over time:

The sticky remnants of the old rubber can be drilled out with a 2 mm drill bit:

(be careful when you try this at home - it is easy to break out the plexiglass corner if one is not careful during this procedure). Once the old stuff is gone, a new piece of 2 mm O-ring can be glued into place with super glue gel. Once the glue is hardened, cut the O-ring snippet to 1mm length above the plexiglass:

Allright! Another Beogram 4000 re-hooded! Soon I will send this beauty back to its owner!