Replace the capacitors in the crossover network

Bipolar capacitors produced for more than 50 years ago are dried out and need replacement.

I will replace the capacitors with some (expensive) MKT film capacitors (metallised polyester film)

I am using some from Bennic and Monacor

Here you can see the old bipolar caps and the new film capacitors.

/Frede

I am going to start the process by replacing these capacitors.

You need to remove the bass speaker and some damping material.

Then you can see the crossover filter.

You can then remove the 4 bolts and careful remove the filter for a more easy restoration.

I don’t remove any wires at this stage.

I only pace the filter at the top of the cabinet and do the work here. I suggest using some protection between the filter and your Beovox 5000.

The process require a few changes to the filter because the new caps are physical much bigger and more heavy.

I will rearrange and I will use hot melt gluing of the caps.

This is the result of the rearranged part for the crossover filter.

The reason for gluing the parts is of course avoiding noise and vibrations.

more to come 🙂

Fascinating - I should really do mine sometime! I am not convinced that the bass units in mine are original though - smaller dust caps.

I think yours are original Peter, the MKIII have been sold with 2 types of bass units - one with 'big dust cap' and one with small dust cap'

/Frede

You may well find there is a significant advantage in replacing the wirewound resistors, modern ones are much more accurrate.

If you measure the values of these resistors, you may well get a shock, mine had drifted massively, you might imagine that a drift of a few Ohm isn't much, but when you are dealing with the low values found in crossover netowrks, that dirft can be over 100%.

How do I know, because I did this same exact thing a few years back.

Make sure to refix those chokes too, the glue will be on the way out.

Don't forget to check out the components on the crossover frequency adjustment controls too.

Casdave,

First, thanks for your suggestions, I will certenly check - and remplacer if needed.

This is really interesting.

What was the final result of your restoration ?

/Frede

The sound was pretty dull and lifeless, and this did improve things, however the addition of the cubes made all the differance in the world.Bass seems to go a bit deeper and less boomy.

It was not a massive improvement, but noticeable. Add up all these little improvements and it can make a big difference.

I also did a pair of Type Ks, the cones were gone at te edges, not an easy repair due to them being corrugated paper types. Now sorting these and the crossovers made a huge difference.The bass response is so much better. I would even argue that they sound nicer than the Beovox 5000.

The type S only needed the capacitors doing, but while you have the speakers apart, it is a good time to refinish the wood too. You'd be amaazed at just how grotty the cloth grilles have become.