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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...

Monday, June 27, 2022

Beogram 4004 Type 5526: Platter Motor, Detector Arm Adjustment and Solenoid Repair

Today I installed the Beogram 4004 platter motor, adjusted the position sensor collector voltage, adjusted the detector arm sensor and fixed a problem with the arm lowering solenoid.

From the checks I made in the previous post I knew there were adjustments that needed to be made on this project.  That is expected when new parts are installed.

I had also noticed that while the Beogram 4004 arm solenoid was engaging to cue the tonearm down, it was not cueing back up correctly.  There was a delay from when the raise tonearm signal occurs and when the solenoid disengages.  We have seen that problem before and it was with the solenoid plunger sticking.

First though...I wanted to adjust the steady state voltage of a couple of the Beogram 4004 sensors.
The adjustment trimmers are both on PCB 1.

One is the position sensor (4IC1) steady state voltage level. I adjusted the 4IC1 collector to 5 VDC using PCB 1 trimmer 1R88.
Note: The 5 VDC voltage adjustment for the 4IC1 collector is made when the tangential arm is at a point in its travel where the position sensor lamp is shining through a clear section of the position scale.

After that adjustment I wanted to get the detector arm sensor adjusted using the new 1R26 trimmer...so I could move the trimmer to its final position on the component side of PCB 1.

I had to change my 1R26 trimmer during this adjustment because my initial 2MΩ trimmer did not have enough range.  The 1R26 trimmer shown below is a 5MΩ trimmer and it allowed me to set the voltage at the 1TR3 collector to 4 VDC (the desired steady state voltage level).

I de-soldered 1R26 from the component side of PCB 1 and moved it to the component side.

After the sensor adjustments I re-installed the Beogram 4004 DC platter motor.
This is the motor that Beolover restored back in January.

Here is a sequence of photos that show installing the platter motor, sub-platter, belt and top platter.

Things look great with the silent running platter motor that Beolover restored.

Normally I would move right into more service manual adjustments but I need to take care of the arm lowering, solenoid problem.

I removed the solenoid assembly so I could take it apart.

With the solenoid assembly removed I ran a check of the coil (it measured good... 9.3Ω) and energized the solenoid (using my 30V bench power supply).

When installed in the Beogram 4004 the Beogram controller applies a voltage of around 30 VDC to the solenoid to engage it.  The duration of that signal is less than 40 milliseconds then it drops down to around 1.8 VDC to hold the solenoid engaged.

When removed from the Beogram 4004 the solenoid engaged at a much less voltage (around 5 VDC and a current of 0.49 Amps).

The problem with this solenoid wasn't engaging though.
The problem was with disengaging.  The plunger was sticking.
When the arm lowering solenoid was disengaged I could feel resistance when manually trying to move the solenoid plunger to the raised tonearm position.

Here are the Beogram 4004 solenoid assembly components.

I cleaned all of the moving parts with acetone and I applied new tape to the coil as the original tape was coming off.

When a solenoid plunger is sticking it is tempting to apply lubricant to the moving parts.
Don't do that.  Oil and grease will make the problem worse and interfere with proper plunger movement inside the guide assembly.
The parts need to be smooth and clean which is why I used acetone to clean them (including the inside of the guide tube).

The solenoid sticking problem is similar to a Beogram 800x tonearm lowering mechanism sticking.
With a Beogram 800x there is a metal screw (used to adjust the parallelism between the tonearm and fixed arm) that sticks to a metal plate when in contact.  The solution there is to apply a thin layer of plastic between the two metal pieces so they don't make physical contact.

The same is true here.  The end of the plunger with the threaded hole for the control rod travels to the end of the guide assembly tube where it makes contact with the metal end stop.

After a period of time the two pieces of metal that make contact start sticking together.  Initially I thought it was a magnetic build up and I tried using a demagnetizer to solve the problem.  It appeared to do the trick but now I think it was due more to my cleaning of the solenoid components.

This time I cut and applied a thin piece of yellow tape (like that used to wrap the coils) to the end of the plunger. That prevents metal on metal contact when the plunger is all the way forward (arm lowered).

I could already see a huge improvement.
Prior to applying the tape I could manually move the plunger all the way forward but had resistance trying to move the plunger back.
Even when I turned the solenoid on end, the plunger would not fall out of the guide.
It just stuck to the end of the guide.
Now, since the metal ends are not making direct contact, the plunger easily slides back out.

Note: The thickness of the material is important.  In the past I tried using a thin, nylon washer on the plunger end as a barrier. The material wasn't thin enough and prevented the solenoid from lowering properly.

The proof is in actually testing the arm lowering and raising so I re-installed the solenoid and gave it a test.

It works perfectly now.  The arm raising is immediate.  No delay.

Note: In the above photos of the solenoid lowered/raised I hadn't re-installed the holding clip on the lowering lever pivot post.  That has been installed now.  In case anyone was worrying I missed that :-).

Now I can get back to the service manual adjustments.

Saturday, June 25, 2022

Beogram 4004 Type 5526: Reassembly for Adjustments and Testing

Today I started reassembling the restored Beogram 4004 parts back into the cabinet base.
My goal was to get the Beogram to a reassembled state where I could do some initial testing.
Things like applying power, checking some Beogram functions...basically an early validation that the restored components work.

Here are some photos of the Beogram 4004 cabinet base as I start adding the components.

Here are a couple of detailed photos of the new transport locks installed when the floating chassis was re-installed. The photo shows the Beolover transport lock bushings installed.

This photo is with the floating chassis locked down.

Here is the unlocked position.

Continuing on with the component reassembly...
Here is the floating chassis with the springs attached.

Here is the cabinet with the PCB 8 Output Board installed.

Next is with the PCB 1 main board, the keypad and the RPM display panel.

That is the minimum reassembly I wanted to do in order to run an initial power on test.
I did add one more item, a servo belt. 

The Beogram 4004 powered up and actually performed most of its basic functions.
The forward, reverse and up/down cueing all worked.  

That's a nice milestone to reach.
I can see a few things that will have to be adjusted but that is to be expected.
In the next post I dive into the service manual adjustments and check sensor signals.

Beogram 4004 Type 5526: Restoration work - Part 4

I wrapped up the floating chassis component tasks by reassembling the tangential arm assembly.
During the reassembly I performed some key lubrication tasks like new PMX - 200 silicone fluid in the lowering damper and a mixture of Rocol MTS 2000 grease with Mobile NUTO H32 oil.  
More modern lubricants are available today but I have plenty of the original lubricants called for in the Beogram 4004 service manual so I like to use those.

I applied some Molykote DX paste (grease) to the two tangential arm assembly rails first.

Then I opened the tonearm lowering damper to clean it and apply some PMX - 200 silicone fluid.

Next I mixed some Nuto H32 oil with Rocol MTS grease for the lubrication mixture on the tangential arm assembly spindle.

The Beogram 4004 tangential arm assembly components can now be reassembled on the floating chassis.

At this point I like to check the tonearm tracking force calibration.
The parts are easy to get to so it is a good place to calibrate the tracking force.

The Beogram 4004 floating chassis (and components) are ready to go into the base cabinet again.

Tuesday, June 21, 2022

Beogram 4004 Type 5526: Restoration work - Part 3

In today's post of the Beogram 4004 restoration work I completed the swapping of the Beogram 4004 RPM indicator lamps with the Beolover LED replacement lamp modules.

I also disassembled the Beogram 4004 keypad so I could clean the contacts.

First the RPM indicator lamps.
The following series of photos show the disassembly of the original RPM indicator lamps.

Now the photos of the installation of the Beolover LED replacement modules for the Beogram 400x RPM indicator lamps.

I have used every version of the Beolover RPM Indicator replacement modules and this version is the best and easiest to install.  Very nice.

Here are the photos of the Beogram 4004 keypad disassembly (to get to and clean the contacts).

The contacts don't look too bad in the photo but a closer shot of the contact points show the contacts to be quite tarnished.

After cleaning the contacts I coated them with some Deoxit and let them dry.

This Beogram 4004 is close to being ready for reassembly.

Monday, June 20, 2022

Beogram 4004 Type 5526: Restoration work - Part 2

I continued the main restoration tasks on this Beogram 4004 today by performing the following tasks -

Replacing the Fixed Arm Record Detection Sensor Lamp with the new version of the Beolover LED Record Detection Sensor Lamp.

Replacing the Tracking Sensor Lamp with the Beolover LED Tracking Sensor Lamp.

Replacing the old Servo Motor damping material with new neoprene closed-cell foam material.

The following series of photos show the steps in replacing the Fixed Arm Record Detection Sensor Lamp.

The lamp and sensor assembly pull out from the front end of the Fixed Arm.

Note that the new Beolover LED sensor lamp leads are bent up a little before the solder connection.
The reason for that is to ensure the lead doesn't short to the mounting rivet of the small board in the Fixed Arm.

Here is the Beolover Tracking Sensor LED Lamp assembly installed on the Tracking Sensor assembly (at the base of the tonearm).

Last...Here is the replacement of the damping material in the Beogram Servo Motor housing.
As shown before, the original damping material has become very dry and brittle.  It is already starting to shed some loose foam material.

Here is the Servo Motor wrapped with new neoprene closed-cell foam.

Re-attached to the floating chassis assembly and ready to be connected again.

Tomorrow I will replace the incandescent speed indicator lamps with the Beolover LED speed indicator lamps.