Beomaster 8000: Step Seven - Replacement of the Speaker Switches with Modern Encapsulated Units and Laser Cut Adapter Plates

The final 'standard restoration task' for a Beomaster 8000 is to replace the speaker switches. My own personal statistics are that in about 50% of all Beomaster 8000s these switches will go bad in the near future if they are used regularly, like for headphone listening etc...They are usually corroded on the inside and frequently when a Beomaster is used again after a long period of storage, they break after a few uses and then the outputs are no longer connected to the speaker jacks. This shows the speaker switches flipped out of their 'compartments' for accessing the solder points:

Note the brown PCB-like base plates that hold the contacts...this switch style has long gone out of fashion in favor of fully encapsulated modern designs that are capable of millions of switchings before they need to be replaced. Unfortunately, these modern switches do not have this base board anymore, and hence they do not fit into the compartments under the heatsink cover. I designed laser-cut adapter plates that mimic the original base plates while snugly fitting the footprint of the modern switches:

This shows them after soldering them in:

And situated in their compartments:

All good now in switch land!

Unfortunately, when I gave this Beomaster a subsequent testing of all functions, I realized that the phono jack in the contact box was broken out and also disconnected. Very beo-unlovely! The next post will report about my repair process of these DIN7 jacks.

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!

Beogram 4000: Installation of New Reservoir and Motor Phase Capacitors Using a 3D Printed Adapter

It was time to replace the big capacitors in the Beogram 4000 that I am rebuilding right now. I always enjoy this procedure, especially due to the clean install enabled by my 3D printed adapter. It accommodates smaller modern capacitor units, while giving the entire set-up an organized look. I made an earlier post that shows in detail what leads are connected where, in case you get confused while doing this procedure...there are a quite a few jumpers to re-solder...;-).

Here is a picture of my capacitor kit with adapter (this is available to other enthusiasts - just send me an email). The two back-to-back caps on the left replace the original bipolar AC motor phase capacitor. The adapter has notches that fit to the original capacitor mounting strap holding everything firmly in place:

I used this kit to replace this fairly messy original set-up:

This is how it looks now after installation:

And here a detail picture of the connections:

On to recapping the PCBs and adjusting the motor trimmers.

Beomaster 8000: Replacing the Speaker Switches with Modern Encapsulated Units and Laser Cut Adapter Plates

After my second round of output PCB troubles in the Beomaster 8000 that I am restoring right now, I put in new speaker switches. The heatsink cover was still off, so this was a 'good moment'. I implemented modern encapsulated switches and laser cut adapter plates that make them fit into the original bays for the switches. A while ago I made a short video about this process, that also shows the laser cutter in action...what's not to like about digital manufacturing methods!:

These pictures document the procedure on the particular Beomaster 8000 that I am rebuilding. This shows the original switches in place:

Here they are 'folded' out and the original mounting plates are visible:

This shows the original switches in comparison with the new replacements and their adapter plates. Note that the here used most recent design iteration has laser etched tabs on the narrow sides of the plates since I was not able to find plexiglass sheets of the same thickness as the original base plates of the switches:

These switches and adapter plates are available to other enthusiasts, just send me a message.

Here they are soldered in place:

This picture shows them held in place in their bays. The laser cut plates exactly fit in the cutouts and the precisely laser etched thickness of the tabs ensures that the switches are at the right height when the heatsink cover is installed:

Beomaster 8000: Replacing the Output Reservoir Capacitors

SinceI had the Beomaster 8000 heat sink cover off while working on the output stages it was a good moment to also replace the original 10000uF reservoir capacitors. I always enjoy replacing these with modern units and my custom designed 3D printed adapters to make them fit snugly into the original bays. Here are a few pictures:

Here is a shot of the replacement units with their 3D printed adapters (these adapters are available to other enthusiasts - just send me an email). I currently use quality Japanese 105C caps from United Chemi-Con (EKMH630VSN103MA50M):

This shows the original capacitors of the left channel:

And after installation of the replacements:

Here is the original right channel:

And the replacements installed. I had to put on shrink tubing (yellow in the photo) onto the original leads to make them short circuit proof. Some amateur overheated the insulation while messing with something back there and it was a bit frayed at the ends.

On to the speaker switches!

Beogram 4000: Replacing the Reservoir and Motor Phase Capacitors

I completed the recap of the Beogram 4000 on my bench by replacing the reservoir and the motor phase capacitor. I recently developed a 3D printed adapter for that, which secures the new smaller capacitors in the location of the old ones using the original mounting strap. This post gives more detail about the replacement process and a detailed 'wire map' of all the connections that go to these capacitors. It can get a bit confusing when doing this for the first time. Here are a few impressions from this particular Beogram 4000:

This shows the original cans:

This is the replacement assembly with the new capacitors placed into the 3D printed adapter. This shows how to prepare the capacitors to accept the wiring. Note that the two capacitors on the left are the replacement for the unipolar original 150 uF motor capacitor. I use two 300uF caps back to back:

And here is a shot of the installed assembly:

Like all the parts that I develop, this is assembly is available as a kit to other enthusiasts. Just send me an email.

Beogram 4000: Replacement of a Stuck RPM Relay with a Modern Encapsulated SMD Relay

The Beogram 4000 that I am currently restoring was not able to switch the AC motor to 45 RPM. After replacing the incandescent light bulbs in the control panel it became clear that, while the 45 RPM button would properly illuminate the 45 trimmer pot, the motor would not change its speed. I traced the signal, and it turned out that the relay was broken. The relay simply switches different resistor networks into the feedback of the Wien oscillator thereby changing its resonance frequency.

The issue with replacing vintage relays is that modern units usually are much smaller and also have a more standardized footprint. This vintage relay actually has an unusual pinout in that the two throws are not mirrored across the relay like in modern units, but are different. The translation between modern and vintage relays was made with a breakout board that matches the pinout of the original relay.

I made a short video about this process. It explains the circuit and gives a demo of the new relay click. This is important in my opinion, due to need to get an audible feedback when pressing one of the RPM buttons. All other buttons give a direct mechanical feedback, i.e. this seemed important. Here is the video:

Here are a couple high res shots of the breakout board. Front:

And back:

This design drops directly into the solder points of the original relay.

Beogram 4000: Reservoir and Motor Phase Capacitors Replacement

I recently supplied a customer with reservoir and motor phase capacitors together with my 3D printed adapter for his Beogram 4000.

He reported that he was only able to measure half waveforms at the AC motor of his newly acquired Beogram 4000. This indicated issues with the phase capacitor or the power supply reservoir capacitors. He installed my kit and the problem was fixed. Here is the link to my original post about this procedure. Another Beogram 4000 back in service! He sent me these great pictures:

This shows the new capacitors and the red 3D printed adapter that holds them in place using the original mounting strap of the original, much larger, capacitors:

And here some impressions of the deck back in service. What a beautiful design!

 

 

 

Beogram 4000: Replacing the Reservoir and Motor Capacitors Using a 3D Printed Adapter

Today I received the 3D printed adapter for the new reservoir and motor capacitors of the Beogram 4000 that I am currently rebuilding. Modern capacitors are considerably smaller than the original  1970s types, so a 3D printed adapter makes for a clean implementation with no wiggly or loose parts. 

Here are a couple impressions of the assembly with the new caps:

I replaced the original 150uF unipolar motor capacitor with two axial 300uF types back to back. The other capacitors are Rubycon, Panasonic and Multicomp 105C types for a long lasting setup. 

********Update: See here for a detailed view of how to prepare the replacement capacitor assembly before soldering the wires to it***********

This is the first time that I work on a 4000, hence, before I took the original setup apart, I made a detailed schematic of the wiring for the record in case there is confusion at some point during the operation. Mixing up some of the wires could potentially cause considerable havoc:

Then I unsoldered everything and put in the new capacitor assemblies:

Here is a detail shot of the classic Zener diode-based 24V emitter follower regulator setup. The regulating transistor is directly bolted (via an insulation pad) to the cabinet metal bottom for heat dissipation. The metal bar across the setup also serves as collector terminal. The Zener diode is the short can that is soldered between the current limiting resistor/transistor base node and the negative ends of the 3300uF reservoir caps that serve as system ground:

After a thorough double check of all connections, I plugged the Beogram in, and started it up. Everything seems happy! This is Beolove!

Beomaster 8000: Replacing the 10mF Reservoir Caps

After doing the speaker switches of the Beomaster 8000, the logical progression is to replace the main reservoir capacitors for the output stages. These 10000uF capacitors often loose part of their capacitance at this age, which causes ripple in the power supply and limits the responsiveness of the outputs during loud impulses. Since new capacitors tend to be considerably smaller, I use 3D printed adapters (on a Makerbot II) for the new 105C types:

At this stage the Beomaster is typically completely opened up:

This are the original capacitors of the right channel:

And after replacement with the new ones:

And here the left channel:

And after installing the new ones:

After I was done I measured the old capacitors, and found that two of them had very low (~2.4mF) capacitance values, definitely out of spec:

I expected this since their tops look slightly bulged, usually a sign for trouble.

The remaining tasks with this Beomaster are recapping the preamp, filter and tone control and the two FM boards, and then fixing the latch of the control panel cover. I am curious how this will turn out...I just received the 3D printed replacement parts for the maimed latch this Beomaster came with, but I can only try the parts out, after I put the Beomaster back together. We will see soon!

Beolover 8000: Speaker Switch Replacement with Modern Switches

A fellow B&O fan asked me if my recently developed speaker switch adapter plates for the Beomaster 8000 would be available. I was happy to oblige, but felt like I needed to improve my design a bit for a more satisfying experience. I wanted larger holes for a bit for a better fit of the solder tabs of the switches. I also wanted to cut them from thinner plexiglass to avoid the Dremel step for thinning the tabs for precise fit into the switch compartments of the Beomaster. Another goal was to achieve a press-fit of the adapters onto the PCB board alignment tabs of the switches to avoid the glueing-step to affix the plates to the switches.

Here is a picture of the redesigned adapters with fitted switches (the adapters were cut from 1/16 strain relieved plexiglass):

I also made a video about the process (including a shot of the laser cutter in action - awesome!!..;-). Enjoy!:

Beomaster 8000: Replacement of Speaker Switches - Laser Cut Plexiglass Switch Adapters

I always replace the speaker switches when I restore a Beomaster 8000. They are often corroded, and I experienced several failures in my own Beomasters (I often use my Sennheiser RS180s, and therefore need to switch the speakers on and off fairly frequently...). The issue with these switches is that the original model was designed with a high density board base, which had installation guide tabs on the side. The Beomaster housing is designed with bays that fit these tabs exactly. All new switches seem to be fully enclosed in plastic. While the general form factor is still available, in the past I had to extract the high density boards from the old switches, modify them with a Dremel, and then glue them to the bottom of the new switches. See this post for the original procedure:

http://beolover.blogspot.com/2014/03/beomaster-8000-speaker-switch.html

I never really liked the Dremel job...not precise enough for my taste. Recently, I learned to operate a laser cutter. What better first project than designing a nice adapter plate, which would align the new switches precisely to their compartments??

I cut the adapter platelets from 5/64 plexiglass (this is a bit too thick, but that is all I had at that point). That meant I still had to put the Dremel to them to reduce the thickness of the tab areas to about 3/64, the thickness of the high density board. If I do it again, I will cut the entire adapter board from 3/64 plexi or something similar. This shows the new switches in comparison with one of the old ones and the laser cut adapters. Note the slits, the board mounting guides of the switches fit snugly into them, aligning the switch (BTW: I used No.: 611-S201031MS02Q from Mouser) with the adapters.

Here after glueing the adapters to the switches and Dremeling the tabs thinner:

Here are a few pictures from the installation process:

Original switches removed from their compartments for desoldering:

New switches installed (it surprised me how durable the plexiglass was during soldering...no issues with melting, warping etc...):

In their compartments:

And with heat sink cover installed:

Perfect!! These new switches are much smoother than the old ones and are guaranteed for a few million switchings! On to the display board!