Canada Beomaster 8000: Reassembly of Rear Cabinet Components

The rust on this Beomaster 8000 unit is neutralized and the affected metal pieces have been repainted. This receiver is ready for the reassembly of the left and right output amplifier boards, speaker switches and the power supply board.

First though, here are some final pictures of the rust cleanup. Nothing really to say here other than to reiterate that it is better to completely remove the frame parts in order to find any rust areas hiding in the seams.

While everything is open and out of the way I like to change the speaker switches at this point. We do that just to avoid any problems with the old switches in the future. I am using a Beolover speaker switch part for the replacement on this Beomaster 8000 unit.

Here is the speaker switch wiring for the two original switches.

Here is the new switch for Speaker 1

Here are both new speaker switches installed.

Now on to the reinstallation of the left and right output amplifier assemblies I restored and tested earlier.

Starting with the left channel output amplifier assembly...

The opening has a small shelf for the lid damper molded into the cabinet frame. That makes it nearly impossible to slide the output amplifier board into the cabinet oriented the way it will be when installed.

The left channel output amplifier board must be turned 90° sideways to fit through the opening in the frame, then rotated back 90° to its installed position.

Now that the left channel board is in place I will finally solder down the left channel reservoir capacitor wires.

The right channel output amplifier assembly installation is a little easier. The cabinet frame opening for the right channel is much less obstructed.

The final steps are to mount the left and right channel output amplifier assembly heat sinks back on the cabinet frame.

The Beomaster 8000 power supply board assembly is installed and I can now move on to the next part of the restoration.

Note in the above picture that I have temporarily left the metal shield box off the remote control receiver (on the power supply board) until I test that it is working.

Canada Beomaster 8000: More rust to neutralize

While reviewing the last couple of blog posts on this Beomaster 8000 unit from Canada I started to question whether I was sure I got all of the rust. I neutralized the areas I saw inside the cabinet but when I turned the Beomaster over to look at the cabinet's outside bottom plate I saw the same type of suspicious corrosion on the left channel side of the Beomaster.

Maybe at some point in its life this Beomaster cabinet's left channel side was subjected to some corrosive liquid.

I removed the base plate's mounting screws and found some rust areas that were hidden by the molded frame of the Beomaster.

On the frame and rear cabinet panel you can see additional rust and some rust staining.

The frame is non-metallic so I will try some products to remove those. The rear panel is metal so it will need some rust neutralizing treatment.

Again, the right channel side is fine (other than some dust). That reinforces my theory that there was some liquid spilled on the left channel side.

I am glad I removed the bottom plate to check for more rust. This will be easy to fix and while the rust neutralizing treatment is drying I can continue restoring the other Beomaster boards.

Canada Beomaster 8000: Changing the reservoir capacitors and some rust (?)

After an unscheduled little break over the Labor Day holiday it is time to get cracking on these Beomaster 8000 restorations.

This weekend I started on the Beomaster 8000 from Canada, replacing the four 10,000uF reservoir capacitors. These are the reservoirs for the left and right channel ±55V rails.

Starting with the left channel

The solder posts on the replacement capacitors are just a small post and do not provide the nice mounting terminal the original reservoir capacitors had.

To compensate I add a small, flat terminal at each end of the connecting bus-bar.

After that I added mounting terminals to the five wires that connect to the left channel reservoir capacitors. I won't connect those yet because I will need the slack in the wires when I reinstall the left channel output amplifier assembly.

On to the right channel reservoir capacitors.

There is the same issue with the new capacitors and mounting the bus-bar.

Solved the same way.

I went ahead and connected up the five supply wires with their new terminals on the right channel. They won't be in the way for the right channel output amplifier installation later.

I was actually hoping to reinstall the left and right channel output amplifiers after their respective reservoir capacitors were replaced. However, when working on the left channel reservoir capacitors I noticed something odd on the cabinet base that looked like corrosion.

So I took a little detour on my restoration step order.  I went ahead and removed all of the Beomaster 8000 boards from the cabinet so I could fully inspect the inside of the cabinet base.

The corrosion was rather strange. It is only on the left side of the cabinet (when looking at the Beomaster from the front). The areas with the corrosion remove the cabinet black paint when I wipe it with a paper towel.

There is no corrosion on the right side. Just some dust that needs cleaning up.

Back to the left side of the Beomaster cabinet I wiped all of the nooks and crannies that had the rust.

On this type of problem I apply three coats of a rust neutralizer. It will turn the rust black. After twenty-four hours I will check the result and see if any rust has reformed. If it does then I will retreat the areas again. Once the treatment is satisfactory I will be able to paint the inside of the cabinet with black, rust protective paint.

This detour doesn't really hold up progress on this Beomaster project. I can proceed to work on the Beomaster 8000 boards I removed.  I will return to the cabinet in twenty-four hours though to see if it is satisfactory to paint.

Beomaster 4400 (2419): Final Touches and Testing

While starting on the two Beomaster 8000 restorations the Beomaster 4400 has been playing away in my office for several days without a hiccup.  A final series of listening tests are in store for this Beomaster before I pack it up and send it home.

The owner of this Beomaster 4400 receiver has a pair of Beovox M100.2 and Beovox MC120.2 speakers. It so happens that I do as well. So while he may not hook things up like this we felt a nice final test on this restoration would be to spend a couple of days with this Beomaster driving my two pairs of speakers.

But first....
I have been test playing the Beomaster 4400 in my office with the top cover still off. That was so I could monitor the inside as I played it. I wanted to know immediately if the problem with the two main board resistors returned.  That was three weeks ago.  No such problem since and I have been using the heck out this receiver.

Now to the Beomaster cabinet. It turns out it had a very weak rear trim panel and it finally broke.  That called for a cosmetic repair.  I also noticed that the bottom metal cabinet plate had bad rust areas around the cabinet feet.

First the cabinet.
Here is the damaged cabinet piece dry fitted back in place.

For this type of repair I use a slow drying wood glue and clamp the broken piece tightly into place. That will cause excess glue to ooze out the break seam.  While it is wet I wipe all of the excess completely off.  Then I rub in rosewood sanding dust that I collect from some pieces of rosewood veneer I keep handy for these type of situations. The rosewood sanding dust particles darken the light color of the break seam.

There is still a scar but when the cabinet is resanded and treated with fresh oil (boiled linseed oil) it looks quite acceptable in my opinion. It also helps that the break is at the back of the cabinet and on the side.

We thought about substituting a spare Beomaster 4400 cabinet but this is a really pretty cabinet.

Another cabinet fix I tended to was the left front edge. The inner particle board had started to wear away.  It wasn't visible but I felt the amount of material was kind of thin and needed reinforcement.  I made a little mold and used some JB Weld gray epoxy to build the area up again.  It turned out quite nicely.

The last bit of cabinet repair business was the bottom panel rust.
Here is one side of the cabinet base. The screws that attach the feet to the base are rusted and areas all around the rubber feet have rust corrosion.

I was surprised the screws came out without any of them breaking.

Interestingly the bottom panel was the only place this cabinet had any rust.
My fix for this type of problem is to sand down the rust damage until all of the reddish brown rust is gone. Then I wipe away the dust and start applying a rust neutralizer.  I do three coats of neutralizer wiping away each coat about fifteen minutes apart. I leave the third coat on for twenty-four hours.  Then I lightly sand it again.

Now it is ready for some satin black Rustoleum spray paint and new feet.
Speaking of the feet here are the original rubber feet next to the four new feet I am going to install. The feet are about 16mm in diameter and 6mm high.

The new feet have a nice metal sleeve to keep the mounting screw from digging into the rubber.

Here is the bottom panel re-painted and re-installed with new rubber feet and new screws.

There is some visible scarring from the rust corrosion but this is the bottom of the cabinet and the corrosive elements have been neutralized. I feel good about the fix. I could not stand leaving the old feet in place especially with that corrosion going on.

I moved the re-assembled Beomaster to a spare room where I often do some additional listening tests.
That is one reason you can see a lot of wires under the MC40 B&O cabinet.

Speaker placement is (almost) everything when listening to music. I figured I would experiment with various speaker positions during this Beomaster 4400 test but sometimes it just sounds perfect the first time.

This was one of those cases.  The combination of the M100.2 speakers on the inside and the MC120.2 speakers just a little forward and to the side work amazing in this room.  I listened to music for about an hour so far (at around 60dB from 10 feet away).  The dynamics of the music are really good.  The next few days should be a lot of fun.