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Beolover SyncDrive: DC Platter Motor Replacement for Beogram 4002 and 4004 (Type 551x and 552x)

Late Beogram 4002 and the 4004 (Types 551x and 552x), which have DC platter motors instead of the earlier synchronous AC motors usually suff...

Saturday, August 28, 2021

Bay Area Beogram 8002: Capacitor Replacement

On this latest Beogram 8002 turntable project I decided to tackle the capacitor replacement tasks first. I also replaced the phono muting relay while I was doing these electrical tasks...and my soldering iron was hot.

The sequence of working the tasks isn't too important here and I often vary it.

I will start showing the replacement of the two electrolytic capacitors on the floating chassis. They are part of the Beogram 8002 +5 VDC power supply regulation.

These photos go through the replacement from beginning to finish.

As I typically do, I replace capacitors that have values 4.7uF and less with WIMA MKS capacitors. On the capacitors greater than 4.7uF I use high quality Japanese 105°C electrolytic capacitors. 

Next, here is the old and the new muting relay.  The new relay is an Omron relay as was the original.  The new relay however it fully sealed.

I changed out the 4C1 capacitor, inside the transformer box next. It is a bipolar type capacitor used in the tangential drive platter motor circuit of the Beogram 8002. 

The original 4C1 capacitor is quite large which is probably why it ended up inside the transformer box.
The modern replacement capacitor is a much smaller physical size so we like using a 3D printed mounting plate for it when we do the replacement.

Here are the before and after photos.

When I start on the PCB1 and PCB2 capacitor replacement I do usually begin with the microcomputer board (PCB2) first. So that is the case here.

There is only one electrolytic capacitor to replace on PCB2.  That is 2C28 and it is quite important. It is a filter capacitor for the +5 VDC to the microcomputer IC.  

The fit is very tight inside PCB2.  My method of replacing 2C28 now is to cut the leads first to remove it.  Then I desolder the remaining leads.  It is much easier that way with 2C28 out of the way.

I also like to remove the microcomputer IC and replace its 40-pin socket at the same time.

One thing to notice regarding 2C28 is that the negative lead has to be soldered to both sides of the board.  That is important of course and is easy to overlook.

Here are the new and original 40-pin 2IC1 sockets side-by-side.  The new socket is a beefier design with tulip style pins.

Here is the new 2C28 capacitor installed followed by the new 2IC1 socket.

Here is 2IC1 reinstalled. 

It is always worth mentioning that you need to follow good electronic precautions for static electricity when handling delicate integrated circuit devices.

Finally, here are the before and after photos of the main board (PCB1) capacitor replacements.



Another important note regarding the capacitor replacement tasks on PCB1 and PBC2...
A problem we have seen before on the two boards is with the solder connections where the board connectors mount to the circuit boards.  For that reason we always reflow all of the solder points for all the board connector pins.  That is true for other vintage B&O audio components as well.

The main electrical work is done.  I still need to add my test connector to the button control panel that makes the service manual adjustment for the scanning LDR devices easier.  I will do that in the next step along with cleaning the floating chassis, lubricating and adjusting the tangential arm assembly and changing the servo motor belt.

Sunday, August 22, 2021

Bay Area Beogram 8002: Initial Assessment

Another Beogram 8002 is on the workbench for restoration and repair.  

I have found that it is easier to work on repeat Bang & Olufsen audio component types rather than switching from component type to component type. The main reason being it requires configuring the workbenches with replacement parts for a given component so when repeating a component type I have less setup :-).

This new Beogram 8002 restoration project comes from the Bay Area of California.  

The owner looked at our Beolover Blog recommendation for packing and did a great job of preparing the Beogram for shipment.

He double-boxed the turntable and used nice polyethylene foam for the first level of protection.  Polyethylene foam has a little bit of give for cushioning but is very firm so it can protect against punctures and drops. Fortunately this shipment doesn't look like any extreme trauma was incurred.

The inner box containing the Beogram 8002 used softer protective foam that is held in place with shipping wrap. That works really well.

The turntable itself was in a foam bag. Very nice.

Finally, the Beogram 8002 with the dustcover and tonearm compartment lids taped down with good painter's tape.

Inside the dustcover and tonearm compartment foam pieces were in place to prevent any movement of internal parts.  That is extremely important when shipping a turntable. The tonearm and platter can and will move during shipment if they are not secured in place.

My only criticism here was the use of the old fashioned type of styro-foam over the platter area. That type of foam breaks off in small pieces that get everywhere.  I recommend using pieces of polyethylene foam instead. But...I am assuming the owner ran out of polyethylene foam so sometimes you have to make due with what you have :-).

The result is the turntable arrived safely.

One thing I immediately noticed in opening up the Beogram was that the metal lid over the tonearm would not stay up on its own.

The lever piece that fits into the hinge assembly with the damping grease is not attached to the lid.

I have never seen that before. It seems like every project has something new and interesting.

I can also tell that the metal lid attachment to the hinge plate is still the original B&O double sided tape.
It is surprising that it is still attached.  I will address the metal lid issue later.

At this point I wanted to see what state the Beogram 8002 is electrically.
Plugging it in I got the Standby dot. That is a good sign.

Pressing the Turn button started the platter turning.
So I went ahead and pressed the Play button.

The platter started again and the tonearm moved to the first set down position (since I don't have a top platter installed yet).

The speed locks in without any trouble but the arm assembly will not move either forward or backward.
The Stop button does not result in the arm returning.  

These type of issues are typical and can be due to a number of things.  All will get resolved in the restoration process.

With the tonearm assembly stuck out over the platter area it sometimes requires unplugging the Beogarm and manually turning the spindle to get it back home.

In this case I tried another trick that sometimes works. 
I unplugged the Beogram and installed a top platter.
When I plugged the Beogram back in the fixed arm detector saw the empty platter and the logic in the Beogram determined it needed to return back to the home position.

That exercise gives me a little information of the electrical problems with this Beogram 8002.

I can now proceed with disassembling the rest of the components and continue the assessment.

Looking under the removable deck lid for the tonearm compartment I discovered that the B&O double-sided tape holding that panel assembly had deteriorated. No surprise there.

Before getting to the point of opening this Beogram 8002 up into the service position I want to look at the dustcover assembly.  I already know the tonearm compartment lid has a problem so I plan on removing both the dustcover and tonearm compartment lid before opening up the cabinet for service.

The dustcover opening mechanism is working perfectly on this Beogram.

With the dustcover raised I disconnected the spring mechanism that controls opening and closing the lid.

I removed the leaf spring assembly for the dustcover lid to get it out of the way.

I lowered the dustcover back down and checked the back panel of the cabinet.

Many Beogram 8002 units have had the back panel of the hinge assembly pulled off where the plastic tabs are broken.  In those cases the dustcover/tonearm compartment lids easily come off together with the back panel.

In this case the back panel hinge assembly is good and tight. It looks like the mounting tabs are still intact.  

For that reason I prefer not to disturb it and risk damaging any of the mounting tabs. It is a bonus if the back panel is this nice and secure to the cabinet.

My method to remove the dustcover and tonearm compartment lid in this case is to pull the metal bar for the hinge. That releases the lids and doesn't disturb and any of the attachment pieces.

Interestingly, on the hinge area for the tonearm compartment lid there appears to be a bunch of glue residue. I can't tell if that is from some previous technician gluing the back panel in place or glue from an attempted repair of the lid hinge (that is detached).

In either case, I have some glue residue to clean.

Now that the tonearm compartment lid is removed I am thinking that the best restoration step for that component is to replace the lid with a spare that has the lowering hinge mechanism intact.  

The dustcover and tonearm compartment lids are now removed and put away for later.

I am about ready to detach the floating chassis so I can open up the Beogram to its service position.
I decided to go ahead and remove the Beogram's transformer assembly first. 

Inside the compartment where the transformer came out of there were the remains of an intruder.  Fortunately it is no longer alive.

It is surprising where spiders end up.  They seem to like Bang & Olufsen though.

After removing the three floating suspension spring clips I opened the Beogram into the service position.

I removed all of the internal components from the Beogram 8002 cabinet and laid them out for restoration.

I didn't find anything unusual or any surprises with the internal components. They appear to be mostly original parts. One capacitor looks like it might have been replaced in the past but that is all.

Here is the Microcomputer box opened up. The thermal grease is pretty dried out.  Replacing that is part of a normal restoration anyway.

The transformer compartment looks good. The capacitor for the platter motor drive will get replaced.

The two capacitors on the floating chassis for the +5 VDC power supply regulation will get replaced.

I will check the forward and reverse scanning sensors as well as install a test connector for their adjustment. They are located on the underside of the control panel.

The small phono output board with the muting relay looks good.  I will replace the relay with a new, sealed one.

The servo motor pulley for the tangential arm spindle worked but it is cracked and will be replaced.

It looks like the tonearm is not horizontally parallel with the fixed arm. That will get adjusted correctly when I do the service manual adjustments.

To remove the subplatter (or rotor in the case of the Beogram 8002) I had to move the speed sensor out of the way because the rotor component would not detach from the center hub.

With the speed sensor assembly rotated out of the way I could remove the hub and rotor.

It looks like the rotor was glued to the hub with some sort of epoxy.  I was able to separate the components but normally the rotor is attached to the hub with some tacky type glue that removes easily.

I will use a removable, tacky type glue when I reassemble it.

I don't see any real problems with the Beogram 8002 inner components though. Nothing that can't be made like new again.

Here is the floating chassis with the rotor and hub removed.

The areas with problems on this Beogram are cosmetic.
The tonearm compartment lid most likely needs replacing.
The tonearm compartment deck lid needs the old double-sided tape residue removed and reattachment with some new, VHB type tape.
The dustcover fixed-hinge mount for the raising and lowering mechanism is securely attached but with the original B&O double-sided tape.  That should be replaced with epoxy.

Finally there is this.

The aluminum deck around the platter area seems secure but I can see a gap and a closer look shows that it has been replaced by some white, foam type, insulation tape. I have seen that on other Beogram 8002 units. It will hold but it doesn't look right.
I recommend pulling the deck off, removing the white, foam type tape and replacing it with some 0.8mm VHB tape.

This is a nice Beomaster 8002. The electronic issues are all things that I have seen before and should easily go away with replacing the old electrolytic capacitors, reflowing solder joints and performing the service manual adjustments.