Texas Beomaster 8000: FM and FM Interface Boards

The two FM boards on the Beomaster 8000 were a slightly different story than the Canada Beomaster. The restoration task was the same as the two from Canada....cleaning, reflow solder joints and replace capacitors.  However, I discovered some corrosion on the board around one of the board connectors so that had to be dealt with.

Here they are as I received them.

I removed the board components I was replacing.  You can see the corroded area I am talking about.

I continued with the cleaning to see how much of the corroded area cleaned up.

Not bad but there is still some corrosion residue present. The board connectors on that side of the FM board don't look all that healthy to me either.  I will most likely replace the trimmer resistors nearby but I will wait until I am into the Beomaster functional testing.

On the trace side of the board you can see some corrosion on the metal shield plate.

Fortunately I did have a couple spare Beomaster 8000 FM boards. They are a couple of boards that have damage board traces so they won't be needing their shield plate and connectors any longer.

I replaced the old, corroded parts with the spare boards.

These two boards are now completed.  That is much better.

Beogram 4002: New Project From Houston

I get to switch gears from Beomaster restorations back to a Beogram project next. I love working on both so either way it is a treat for me. A gentleman from Houston brought me a couple of Beogram 4002 Type 5513 turntables he had acquired some years ago. Eventually they began to age and stop functioning correctly.  Like most Beogram 4002 owners he found that he missed playing vinyl records on them so he had to get them restored.  I am lucky enough to receive the task and look forward to getting these back 100% working again.

One at a time though.

These were functioning well for the owner not too long ago so the Beograms are in decent shape. Here is the first Beogram turntable opened up.

I already removed the DC platter motors back in March and sent them to Beolover for a full restoration. I have those motors back and they have been waiting for the rest of the Beogram restoration to catch up.

There are a few areas inside this Beogram where rust is starting to look bad. I will clean those up and put a stop to the rust. 

The Beogram phono DIN plug is badly corroded as well and the best solution there is to replace it.

Here are a couple of pictures of some of the chassis components that have rust.

Interestingly this Beogram 4002 is one of the rare few I have seen where the plastic transport bushings around the floating suspension locking screw are still intact. They are still soft and in good shape. Most of the units I see have brittle bushings that have cracked and are in a million little pieces scattered throughout the Beogram. I will treat the bushings with some plastic restoration fluid that will keep them from drying out.

The main circuit board looks in great shape. No signs of heat stress or corrosion there.

The tangential arm assembly also looks to be in good condition. 

Recapping the main board, replacing relays and speed trimmers along with cleaning and adjusting the tonearm mechanics should get this turntable back to working the way it was designed. The restored platter motor along with the replacement of the trimmers and speed indicator lamps (with Beolover's LED replacement modules) will have this Beogram spinning vinyl better than ever.

Time to get to work.

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!

Beomaster 8000: PCB 1 and 2 (Tuner) Recapping

Today was Tuner Day of the current Beomaster 8000 restoration project. The tuner worked basically fine, but there was an intermittency on the right channel, seemingly depending on the moon phase...;-). Tracing the signal with the oscilloscope, revealed immediately that one of the contacts in plug P6 was poor. I pulled the boards apart (they come out together...), and cleaned the contacts with a fiberglass pen and bent them a bit for added contact pressure. Then I added a coat of DeoxIT D100. As usual, this seemed to do the trick. Wiggling the boards did not cause problems in the right channel anymore! Here is a pic of the contacts before cleaning...some black oxide spots are clearly visible where the female headers made contact:

Such black spots come easily off when using a fiberglass pen on them. I forgot to take a picture, but one can achieve as-new looks that way. The DeoxIT further cleans the contacts and provides a protective layer against future oxidation.

While the boards were out, I also recapped them with quality 105C caps. An uneventful procedure. Here is a picture of the boards before the procedure:

And after:

And a detail shot of the region around the IF stage (CA3189E):

Well, almost done!! On to the preamp board (PCB #3)...

Beomaster 8000: Rebuilding the Filter and Tone Controls Board (PCB #4)

Today I took the filter and tone controls PCB of the Beomaster 8000 out and replaced the capacitors. This required unsoldering the signal strength meter leads from the PCB, and unscrewing the plastic panel that holds the switches, buttons and sliders. Here is a pic from the bottom of the PCB before taking it out:

The meter in the lower left corner needs to be unsoldered to be able to remove the PCB from the plastic cover. Five screws hold the PCB to the plastic cover. It is important that these screws do not get tightened too much when re-installing the board. The plastic standoffs can easily crack.

Here is a photo of the meter after unsoldering the leads:

This is a pic of the board after removing it before replacing the capacitors:

And with new caps:

Several of them needed to be tilted to accommodate for the low clearance between the plastic cover and the board. This PCB also had one cracked ceramic capacitor (C207).

I replaced it with a new 10nF type:

After screwing the plastic cover back on (it is a bit difficult to get all the buttons and sliders slotted at the same time - patience helps...;-) I soldered the meter leads back onto the board, and tested the Beomaster...seems all works fine. On to the tuner boards.

Beomaster 8000: Replacing the Speaker Switches

Time for the Beomaster 8000 speaker switches while the heat sink cover is off. Another 'standard rebuilding task'. These switches are corroded in most 8000 units, and when used consistently will fail soon. I often switch between headphone and normal speaker operation, and these switches failed in all three of my personal 8000s after a few dozens switchings. Hence, they must go. Luckily, there are almost identically looking modern encapsulated replacements available. See here for more details on part numbers etc...:

http://beolover.blogspot.com/2011/10/beomaster-8000-speaker-switch-repair.html

I used pretty much the same procedure in the current restoration project, except that I directly drilled holes into the base plates, instead of messing with the Dremel tool...can't beat experience! Here are some pics:

Original switches from bottom:

After I removed the bottom plates from the old switches and drilled holes into them to permit the pins of the new switches to protrude:

After glueing them together. This establishes the original form factor that they fit into their compartments:

After soldering them in:

And in their compartments: Like it never happened...;-)!

The control panel is next! Slightly dicey affair due to the often cracked plastic receptacles for the screws, and the buttons and sliders that need to be refitted in their proper places during re-assembly. I always wish I had four hands to do that!

Beomaster 8000: Speaker Switch Replacement

Further inspection of the Beomaster 8000 yielded difficult to switch speaker switches. As in most 8000s of this vintage these switches are corroded and most fail within a short time if used consistently. We decided that the switches needed to be replaced with new ones. Here a couple pics of the old ones:

and bottom view:

Unfortunately these switches are not made anymore. Technology has progressed, enabling fully enclosed plastic packages. To fit new switches to the compartments of the Beomaster 8000, the old-style PCBs that formed the bottoms of the old switches need to be transferred to the new ones. I took the old switches apart by Dremeling the plastic 'buttons' off that hold the PCBs to the plastic  enclosures, and drilled holes into them to allow the pins of the new switches to protrude:



Then I glued the PCBs to the new switches:

And the final product:

Time to solder them in:

And installed in the 'compartments':

Testing yielded a smooth operation. Much better than the old ones! Time to give the Beomaster 8000 a spin!