Beomaster 8000: Step Three - Replacing the Main Reservoir Caps

No power supply restoration of a Beomaster 8000 is complete without also replacing the four big cans in the back. They are the reservoir capacitors for the output amplifier ±54V power rails. One 10000 uF capacitor per polarity and channel - massive! That gives the Beomaster 8000 its excellent output stability at 150W per channel. Awesome!

Here are a few impressions of my process:

This shows the original capacitors on the right side:

I unsoldered and pulled them out and replaced them with modern 105C grade Japanese units. As usual, modern capacitors are a bit more compact than 1980s types. That is why I use 3D printed adapters to fit them into the capacitor bays of the Beomaster 8000. This picture shows the original capacitors and the modern replacements with their 3D printed adapters:

The adapters and capacitors are available as a kit, just send me a message using the contact form on the right

After the installation it turned out that I broke off one of the resistors at the thermal switch for the right side:

This happens frequently when pulling out the capacitors, since the resistors are in the way, and they cannot take much bending. I replaced both resistors with new ones:

Then it was time to turn this 8000 around and do the left side:

After replacement:

After this I measured the capacitance of the original caps and of course they were out of spec (they usually are at this point):

4000uF is less than half of the specced 10000uF, but this would still have worked at moderate volume settings. But of course, the caps would have failed in the near future. So it was the right thing to replace them now for piece of mind. 

An then it was finally time to turn this Beomaster 8000 on for the first time:

And of course, one of the segments in the input display was a no-show. No problem, since I usually rebuild these displays anyway with SMD LEDs to ensure stability in the years to come. These displays all will fail in the near future, i.e. it is almost better to buy a Beomaster with failed display for less money and then fix it. That way one has a Beomaster with displays that will likely last another 30 years.

On to recapping the rest of the unit!

Beomaster 4400: Replacing the Main Reservoir Capacitors

Today was output capacitor day in my Beomaster 4400 restoration process. I always enjoy replacing the 'big cans'. It certainly has something satisfying to it. Also, it turned out that this Beomaster definitely needed new ones. It is a fairly painless operation in these units, since the capacitors are only held in place with one clamp, and the grounding wires are well organized on the center bridge of the capacitor assembly. The clamp is even adjustable, i.e. new smaller diameter capacitors can be fitted without the need for adapters. Here is a picture of the original setup:

Here is a shot of the empty bay after removal of the old caps:

This shows the new ones loosely fitted:

After fixing them in place with the clamp it was time to solder them in. I usually use 'helping hands' to hold the wires in place. It is important to insulate the wires from the alligator clamp with some cardboard to avoid them melting through the insulation while the leads get hot during soldering:

And don't forget to put the cable tie back in!..;-). Done:

As usual I measured the old caps, and this ones, while looking o.k. definitely showed signs of their endgame. Their capacitance was out of spec (should be 10,000uF). The 4400 still worked with them, but would have probably shown signs of distortion if played loudly:

On to replacing the remaining electrolytic capacitors in this vintage beauty!