Canada Beomaster 8000: Power Check Milestone Reached

I mentioned in the last post on this Beomaster 8000 from Canada restoration that my next step was to check the restoration work so far by performing some power checks. That means connecting up all of the boards, plugging the Beomaster power plug in and checking the DC supply voltages.

That milestone has now been reached. Plugging in the Beomaster yielded no surprises and the expected red dot standby LED illuminated.

Pressing the PH (phono) button on the control panel illuminated the volume level and PH segments on the display.

The Beomaster appears to have power so it is time to measure the DC supply voltages.

First is the +5 VDC supply reservoir and the output of the +5 VDC regulator.

Very good. That check was pretty much redundant as the red LED dot would not have illuminated if the +5 VDC supply wasn't working. But I like to see what the actual voltage is.

Next are the ±15 VDC supply reservoirs and voltage regulators.

Those all check out. Now for the ±55 VDC rail voltages for the left and right channel output amplifiers.

All voltages are present and accounted for. That is a major milestone in the Beomaster 8000 restoration. From here it is to return and complete the work on the microcomputer and display boards.  After that I will reassemble the Beomaster 8000 for functional testing.

With the power applied to the Beomaster I was able to see that there are some failed display segments. The plan was to rebuild those displays anyway so that confirms it is necessary.

Beogram 4002: DC Motor Restoration

A Beogram 4002 DC motor from London in need of restoration recently arrived. Most Beogram 4002/4004 DC motors are in need of getting their Oilite brass bearings re-infused with fresh oil at this point in time. The oil stored in these porous brass bearings is drawn out over the years, resulting in dry bearings that are the main cause of RPM variations in Beograms. This shows the motor as received:

Extraction of the bearings requires disassembly of the motor:

The two small donuts on the black pad are the bearings. I put them in motor oil and pulled a vacuum:

The air bubbles emerging from the bearings indicate the air drawn from the bearings due to the vacuum. This makes room for oil diffusion into the bearings. After about 48 hours the bubbling stopped and I extracted the bearings from the oil:

Then I re-assembled the motor and installed it in one of my Beogram 4002s for a 24 hrs RPM stability test with my BeoloverRPM device,

which allows logging of the RPM over extended periods of time. A great tool to check the health of a platter motor, since RPM fluctuations usually are inconsistent over time, and it is difficult to pinpoint issues by listening to records alone.

This is the RPM graph that I obtained after about 24 hrs:

This is as good as it gets...this motor is back in business and will soon travel back to its Beogram in London!

Texas Beomaster 8000: Final four capacitors replaced

Like the Beomaster 8000 from Canada I replaced the last four capacitors on the Texas Beomaster.  My original plan was to run some power supply checks with the recapped Beomasters. Unfortunately this Beomaster 8000 from Texas has a few additional problems with the last two boards. The problems aren't anything that can't be fixed but rather some things that must be reworked. This Beomaster from Texas was worked on before. Whoever put a soldering iron to this receiver did a poor job. I already have had to fix some bad solder joints on other boards in this unit. The microcomputer and display boards also have some ugly solder joints.

I started with the microcomputer board.

Removing the top and bottom covers of the metal shield box reveal the microcomputer components.
This Beomaster is missing a paper insulator piece that fits on the inside of the bottom cover. I will make a replacement for that.

There are quite a few jumper wires on this board compared to the pristine board from the Canada Beomaster unit.  That doesn't mean the wiring is incorrect.  I have seen several other Beomaster 8000 units where updates to circuit boards were made in service centers after the units had left the factory.

The problem with this wiring though is that it looks pretty sloppy.  Here is a closer look at some of the soldering on the wiring.

There is no way that was done by a professional B&O technician.

I will go ahead and get the two capacitors on this board replaced but will have to do a bunch of rework on the sloppy solder joints before I begin using this board.

Here are the two capacitors being replaced.

Here are the replacements installed.

The display board is next. It is in decent shape.

This board had a bad soldering pad for one of the capacitors being recapped and I found a diode lead that was barely attached to its pad.  I fixed both problems.

I still need to reflow all of the solder joints on this board before using it.

Canada Beomaster 8000: Final four capacitors replaced

There are just four remaining capacitors to replace on the Beomaster 8000 from Canada. Two capacitors each on the microcomputer board and the display board.

The microcomputer board on this Beomaster is about as pristine as you will find. No need for any board cleaning on this beauty.

The two capacitors to replace on this board are inside the metal shield box. There is a top piece to the shield box (shown above) and a bottom piece shown here.

The inside of the bottom cover has a paper insulator to keep the metal cover from shorting component leads.

Here is the inside of the box (front and rear)

I will say it again...this board is in beautiful condition. The two capacitors to change out are a 1uF and a 22uF capacitor.

I am only doing the two capacitors on this board for now. I want to check the Beomaster 8000 power supply so I will re-install this recapped microcomputer board for that test. Once the power supply test is verified I will come back to this board and change the two oscillators as well as reflow a number of solder joints.

I will do a similar thing with this Beomaster's display board.  For now I will just change out two capacitors on that board but will return to it later for the restoration of the segmented displays, replacing the four incandescent lamps and reflowing solder joints.

Here is the display board as I received it.

The two capacitors are easy to get to so I quickly changed them out.

Here is the completed board.

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.

Canada Beomaster 8000: FM and FM Interface Boards

The Beomaster 8000 FM section is on two boards, the FM board and FM Interface board. The restoration task on these two boards is primarily cleaning, replacing capacitors and reflowing solder joints on the board connectors.

Here are the two boards as they were received.

I removed the components that are being replaced then cleaned the boards.

I didn't run into anything dramatic on these two boards which is how I like it. Several of the removed capacitors were out of tolerance.

I replaced the capacitors 2.2uF and under with WIMA MKS capacitors. For values higher I replaced using 105°C rated electrolytic capacitors.

Here are the completed boards ready to be reinstalled in the Beomaster.