Beogram 4004 (5526): Installation of New Transport Lock Bushings

The Beogram 4004 (5526) that I am restoring right now had the orange type of transport lock bushings, which are prone to degradation. This was evident immediately after taking the Beogram out of the box, since there were telltale orange plastic fragments all over the place:

This shows the left transport lock without its bushing:

I removed the floating sub-chassis of the Beogram, which revealed the degraded remnants of all three transport lock bushings:

I vacuumed the enclosure, and then it was time to install the new 3D printed bushings:

Each bushing has two parts, one to be inserted from each side of the lock orifice. Like all parts featured on this blog they are available to other B&O enthusiasts. Order them directly via the Beolover Shapeways store. Six parts are needed for all three locks. This shows the lower part of the left lock:

And with the sub-chassis outfitted with a new bushing installed:

I also did this for the other two locks and then I replaced the top halves of the locks:

Now this Beogram can be shipped again without fear for damage due to loose transport locks.

Beogram 4002: Final Tasks, Adjustments & Playing Records

It is time to finish up this Beogram 4002 Type 5513 project. As a continuation of the corrosion damage repair I am replacing the 5-pin DIN phono plug.

Here is a nice reference diagram Beolover created a while back that shows the audio path from the MMC cartridge connector to the 5-pin DIN plug.

I like this diagram because when I am replacing the phono cable plug this shows the phono signals I check continuity on from the Beogram output board connector (P9) to the front of the plug.

Here is a picture of a continuity check for the phono right channel from the phono DIN plug to the output board P9 connector.

I installed a REAN 5-pin DIN replacement plug that has gold contact pins.

A note to other DIY folks that do this - Some of these Beogram phono cables have a cable diameter that makes installing the REAN rubber boot extremely difficult. The fit is really, really tight.

Another phono signal related change I made was to return to the output board and install a grounding switch between pins 5 and 6 of the P9 connector. That is signal ground and shield ground respectively. The Beogram 4002 units come with a separate grounding wire so owners can connect their Beogram chassis ground to an amplifier's chassis ground should there be hum in the signal path.
This grounding switch eliminates the need for that extra grounding wire as the switch can be flipped to short the two grounds together in the Beogram if needed. A nice option and the switch is easy to get to.

One last electrical task is to install the two RPM indicator light replacements (33 & 45 RPM lights). This upgrade of incandescent lamps to the Beolover LED replacement is not for cosmetic reasons. Beolover's ongoing testing of Beogram 4002/4004 DC platter motor stability has shown a positive measurable effect of the LED lamp assemblies over the incandescent lamps. So we recommend them on all of our Beogram 400x restorations.

One weak part of the Beogram 4002 design are the mounting clips for the RPM indicator panel into the control panel. The mounting clips are a hard plastic that often becomes brittle over time and cracks. This unit had a couple of hairline cracks so I applied some preventative patches.

I started the final reassembly of this Beogram unit which includes the service manual adjustments.

The first adjustment is for the Beogram platter height so that the distance from the top of the fixed arm (and tonearm) is 23mm from the surface of the platter. That adjustment is made using the large nut on the platter hub.

The tonearm lowering limit and pickup arm length adjustments are next.

That is followed by vertical and horizontal arm parallelism.

While the platter belt is still removed I adjusted the tangential arm sensor.

Now for the deck panels and the platter position adjustments.

Everything looks good. I performed the arm balancing adjustments earlier so the final adjustments are for the platter speed trim pots.

This Beogram is cleared for record play. I'll give it a listen as I document this blog post :-).

It looks like this Beogram is ready to go back home to Houston. Now where's my copy of "Houston El Mover"?

Beogram 4004 (5526): Restoration of DC Platter Motor

After replacing the incandescent bulbs in the RPM trimmer panel with LEDs it was finally time to restore the DC motor that drives the platter of this Beogram 4004 (5526). This shows the motor extracted from the Beogram:

Restoration of these motors requires infusing the brass sleeve bearings with fresh oil under vacuum. this requires complete disassembly of the motor:

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

Immediately, air bubbles emerged from the bearings as the vacuum drew the air from the empty pores of the Oilite material. This enabled motor oil to penetrate the bearing material, refilling the empty pores. After about 48 hrs the bubbling stopped, indicating that the infusion process was complete. At that point I removed the bearings from the jar:

I reassembled the motor and put it back into the Beogram. Then I installed my BeoloverRPM device to do a 24 hrs RPM stability test:

The BeoloverRPM device is able to log the RPM of the Beogram for extended periods, which is a great way to detect and diagnose RPM stability issues. It is available to other B&O enthusiasts. Just send an email or use the contact form on the right if you are interested. This shows the RPM graph as measured after about 24 hrs:

This is as good as it gets for the Beogram 4004, and we can conclude that this deck is back on track to spin vinyls for another 30 years.

Beogram 4004 (5526): Replacement of Incandescent Bulbs in RPM Trimmer Panel with LEDs

Before the DC motor in a Beogram 4004 (5526) can be restored and tested it is a good idea to rebuild the DC motor control section of the main PCB and replace the incandescent bulbs in the RPM trimmer panel. The RPM stability of the platter drive system depends on all of these components. This shows the RPM trimmer panel as removed from the Beogram:

I removed the covers

and unsoldered the light bulbs:

Then I installed the LED replacement assemblies:

They are drop-in replacements for the light bulbs and include all necessary parts allowing running the LEDs from the 24V supply of the Beogram:

The covers fit like before:

This shows the 33 RPM LED in action:

The LEDs look very similar to an incandescent light bulb. This is the result of using red and green LEDs that are carefully tuned to resemble the emission spectrum of an incandescent light bulb.

Beogram 4002: From Oil Cleanup to First Operational Test

My restoration plan for this Beogram 4002 project encountered a detour. After restoring the main board I intended to do the reservoir capacitor replacement and the output board. However, the rust and corrosion I found when starting the project got me thinking that I need to address that first. Applying rust neutralizer and painting takes time because you have to let the parts dry between applications.

Here are a couple of pictures of the worst rust spots again.

This Beogram is interesting in that it has some really nasty looking rust damage but the overall condition of the turntable is actually really good.

I decided to apply three coats of the rust neutralizer.

After 24 hours I painted the parts with black, oil based paint.

Now I can proceed with the normal restoration. Since I had to disassembly the chassis to get to all of the rusty areas I discovered there were a few puddles of oil in the Beogram. People often make the mistake of applying thin oil to the Beogram turntables...and too much of it.

Thin oil applied to the moving turntable parts end up being slung against other turntable parts. My next step was an oil clean up job.

I had removed the floating chassis to get to the first oil spill.

The tangential arm assembly needs going over anyway so I moved those steps up in my project schedule.

There is a lot of wet oil around the spindle bearing nut. That means thin oil instead of grease was used on the tangential arm drive spindle.

The tangential arm drive spins as it moves the tonearm and you can imagine how that would really throw loose oil like this around.

There was quite a bit of oil on the surface of the floating chassis but I found the most gathering of oil in the tangential drive sensor housing.

The oil could interfere with the sensor preventing it from working properly.
I cleaned all of this area up and put the tangential drive sensor assembly back together.

The tangential arm sensor should be in good shape now when I get to the record tracking adjustment procedure.

I moved on to the arm lowering damper. It was in good shape but I cleaned it and applied some light grease to its piston.

I discovered the tangential drive pulley had small, hairline cracks as most do by now. That makes the pulley deform when the set screw tightens to the spindle shaft. The result is a wobbly running spindle.

I am still amazed that the transport bushings on this Beogram are still really good. That is a rare sight.
Here is the new pulley. It is one of Nick's aluminum pulleys and it works as great as it looks.

I also performed and initial tonearm tracking force calibration. It is easy to work on the tonearm assembly when it is removed like this.

Note that I installed the usual Beolover mod where a small locking nut is added to insure the tonearm counter weight stays where the calibration put it.

That takes care of the initial tangential arm mechanical restoration tasks. Now I can get back to the electrical step of replacing the reservoir capacitor.  Here is the original one as pictured before I started the rust and oil clean up.

Here is one of my favorite Beolover replacement parts. The 3D printed housing with the new reservoir capacitors.

Before this nice assembly I use to glue the new reservoir capacitors to the cabinet floor. This is so much nicer and it uses the original Beomaster clamp.

I am getting close to running an operational test on this Beomaster. First I went ahead and changed the capacitor and muting relay on the output board. I still need to add the grounding switch but I will come back to that.

Here is the before picture of the output board.

...and here is the after.

Now for some reassembly. I have to re-install the rust repaired chassis components so the floating chassis can be put back. I also have to re-install the DC platter motor that Beolover restored for me.

Here are some pictures of various components as they are fitted back into the Beogram chassis.

Whew. It is looking like a Beogram again. I should be able to install the sub-platter, belt and top platter then give this Beogram a test run.

I love it when things work the first time.

Even though this Beogram thinks it is ready I don't trust it enough to try a record yet. I will run through the service manual checks first to make sure it is ready to play a record.