Beogram 4002 (5503): Restoration of Tracking and Tonearm Lowering Systems:

When I restore a Beogram 4002 I always start with the tracking and arm lowering systems, since they are essential for further diagnosis and operation of the turntable. So I went there first with this 5503 type, too. I started with the arm lowering mechanism. Here is a picture of the mechanism:

An interesting detail of the 5503 setup is the solenoid current limiting, which is implemented with a limit switch actuated by a plastic extension attached to the solenoid linkage:

The later DC motor models use an electronic limiting circuit based on a RC delay. This is much more similar to what is found in the original Beogram 4000 models, where a simple leaf contact is used to accomplish this task. The limit switch is definitely a better way to do it. But of course the electronic mechanism is superior to both switch based solution as it not uses mechanical parts.

And after taking out all moving parts except the solenoid. I usually leave it in but give the plunger a dab of silicone grease and work it in.

This are the parts spread out on the bench:

After cleaning the sleeve bearings of the arms and the damper interior with some mineral spirits, I lubricated everything and put it back together. This video shows how to rebuild the tone arm mechanism in detail. I usually adjust the damper when I adjust the tracking system feedback sensitivity since at that point one needs to lower the arm. The next step was lubricating the connecting linkage between damper and tonearm. I took out the sensor arm assembly

and then extracted the linkage for cleaning and lubrication:

This video shows how to get to the damper to arm linkage and re-lubricate it. After I put it back in it turned out that the arms were misaligned. The retaining washer on the connecting linkage was set too loose, which had the consequence that the linkage was not fully pressed against the sensor arm mount. If the arm parallelism is adjusted in this condition, the adjustment is not stable. This is how it looked after I put the sensor arm assembly back in:

Shifting the linkage at the back of the tonearm counterweight set things straight:

After this it was time for the tracking system. This shows the original setup with the incandescent light source installed:

I usually put in a SMD LED based light source in the tracking sensor to make sure it will last for a long time. This is only a small additional effort since the system needs to be adjusted anyway to bring the Beogram up to specifications. The intensity trimmer that is integrated into my replacement part also makes it very straight forward to fine adjust the sensor feedback sensitivity. A great upgrade to consider if you rebuild your own 4002! This part is available. Just send me an email.

This shows it installed:

After that it was time for my least favorite record (free jazz by Sam River) and my dented MMC20EN cartridge to do the tracking system feedback sensitivity adjustment. The goal is to adjust the system that the carriage starts moving after two-three full turns of the record when the needle is lowered on the record.

First, a coarse adjustment is done with the excenter on the base of the sensor assembly:

Once the sensitivity is close to the prescribed 2-3 turns, fine adjustment is done with the integrated intensity trimmer:

After that the mechanism was almost ready for prime time. There is a video that shows the tracking sensor adjustment procedure in detail. Still annoying was the wobbling cracked carriage pulley that caused un-Beolovely vibration during fast carriage movement. Someone previously glued it back together and (nastily) also onto the spindle shaft

I replaced it with a precision aluminum pulley provided by Nick of Beoworld (feel free to send me an email if you want me to put you in touch with him to get your own pulley):

Here is a photo of the installed pulley with a new belt:

I just love how this pulley looks! It elevates the entire mechanism to a much more precise feel. After installing the pulley I cleaned the spindle from hardened lubricants with mineral spirits and then lubricated it with some silicone grease. This mechanism runs now very nicely again. I will adjust the arm lowering limits and the tracking weight once the sub-chassis and the platter will be adjusted to specifications. It does not make sense to do the arm limits at this point since the distance between arms and platter will change during the platter adjustment.

Beogram 4002 (5513): A New Arrival on Beolover's Bench

Over the Holidays another Beogram 4002 (5513) arrived for some TLC. Today I did a first evaluation. The packing job was excellent and featured some new ideas how to safely package a Beogram. Here are some impressions:

The hood was filled with soft foam blocks to hold the sub platter and the RPM panel down:

One of the foam blocks contained the MMC20E cartridge, which traveled well:

Here an impression after taking it out:

I appreciated the precisely cut cardboard that held the sub-platter in place. The arm support also worked very well:

I took the hood off and the back part of the enclosure to give the inside an examination. It all looked original and pretty clean. Then I plugged the unit in and pressed start. The carriage started moving, but at the 30cm set-down point it lowered the arm, but then kept going at a rapid pace. An examination of the tracking system revealed a bent tracking sensor aperture which is stuck in the bulb housing. 

So that definitely needs rebuilding. Also the arm linkages are somewhat hard to move due to the usual hardened lubricants. Nothing that a good cleaning and re-lubricating could not fix.

I also noticed that the motor runs pretty rough, so it also needs to be taken apart and cleaned and it needs to get some fresh lubricant injected into its sleeve bearings.

Other than that, as far as I can tell right now this unit is in pretty good condition mechanically.

Cosmetically, the plinth is in great condition, the aluminum panels could do with a deep clean and the keypad has the usual three-finger usage pattern, but not too bad.

The hood, as usual, could do with some polishing.

All in all no obvious show-stoppers. It seems this unit is a great starting point for a restoration. This Beogram has an excellent potential to be as good as new once I am done with it.

Beogram 4002 (5513): Rebuilding the Arm Lowering Mechanism, Mechanical Adjustments and a Broken SO Switch

Today I rebuilt the arm lowering mechanism of the Beogram 4002 (5513) that recently arrived on my bench. It turned out that all linkages were stuck and that the damper was completely dry. The first step was to re-lubricate the damper to arm linkage and adjust the lateral arm parallelism. I took out the sensor arm fixture to get to the pin around which the linkage rotates:

Then I took the mechanism apart and cleaned everything of the hardened lubricants and re-lubricated with a small amount of silicone grease:

Then I put everything back together and made sure the arms are parallel. Then it was time to extract the damper and the solenoid linkages:

Here is a picture of the damper taken apart:

I lubricated it with a bit of synthetic motor oil and cleaned the old lubricants fro the linkage pivot points and re-lubricated those with silicone grease. Then I put everything back together and gave it a spin. While the arm was now lowering properly, the tracking mechanism was completely out of adjustment due to the arm alignment. So I had to adjust the tracking feedback. Hence it was time to crank out my least favorite record and stick on my dented MMC20EN cartridge to adjust the mechanism:

I made a detailed video about this process, which explains how to do it properly.

Then it was time to adjust the arm lowering limits to help prevent a cantilever extraction in case the sensor in the sensor arm dies. There is another video that shows how to do this. This was the result of my efforts:

The stylus is supposed to just clear the lower parts of the platter ribs when all the way lowered. The final task was to adjust the tracking force. Yet another video shows how to do that.

Then I played a record, which went well, but I had to realize that the 'Switch Off' (SO) switch that turns the deck off when the carriage is in its home position is broken. It is interesting to note how this manifested itself: When the arm returned to its home position on the right, the deck shut down, but the solenoid briefly came on and jerked with a loud 'clonk'. The reason for this is a missing plastic part that is needed to fully engage the switch, i.e. make the ground connection at the right point during the home movement of the carriage. Here is a picture of a good SO switch in a different Beogram 4002:

And here the broken one:

Note the missing small black plastic part right above the carriage pulley. If it is not there the switch terminals are not moved far enough by the aluminum tab on the position ruler preventing it from switching over to the GND pole. However, without the plastic part the switch the switch also forms a ground connection via the aluminum tab on the position indicator slide that is activating it when the carriage has arrived in the home position. This turns the deck off like a working SO switch, but a bit too early and perhaps with a bounce since the spring force between the tab and the switch terminal is weak. Hence the solenoid jerk.

Beogram 4002 (5523): A Second Beogram 4002 (5523) Arrived for some TLC - First Impressions

Another Beogram 4002 (5523) arrived for some TLC. When I took this unit out of the box I realized that the MMC4000 cartridge was still on the arm and that the transport locks were not engaged. So naturally I was a bit worried about the state of the cartridge.

Especially, since it turned out that the foam pads that were supporting the arms had disappeared into he enclosure and the tone arm was swinging freely without any support under it:

I took the cartridge out and gave it a good examination. It seems the low weight of the arm and blue tape underneath the needle prevented the worst and the cantilever and tip survived:

I put the cartridge on the Beogram 4000 that I just restored and gave it a spin. Miles Davis "In a Silent Way" (MOFI reissue). It sounds pretty good, so I think we were lucky on this one.

After this relief I checked out the turntable. The hood is in pretty good condition, probably the best original one I have seen so far. There are a few scratches near the aluminum trim, which is missing the Beogram 4002 insignia. This indicates that the hood may have been polished a bit at some point. It is difficult to get all the way to the aluminum edge with polishing materials, so if not enough attention is paid, there is usually a strip of poorly polished plexiglass. There are also a few telltale swirls across the hood surface.

Then I removed the hood and had a look inside. The panels are pretty good, albeit a bit grimy. Nothing that Mr. Clean Magic Eraser Pads could not straighten out:

Unfortunately, the keypad has a severely damaged START key, where the coating is worn to the metal surface:

Otherwise the exterior is pretty good, excellent veneer corners, but, unfortunately there is a scratch in the veneer up front:

Maybe this can be sanded/polished out.

Below deck the main damage is fully disintegrated transport lock bushings of the orange type. The orange ones are always crumbling, while the grey ones typically can be left alone. That the transport locks were not engaged did not help this issue since there must have been constant impact on the bushings during the rigors of shipping.

At any rate this is not difficult to fix, and the 400x units are of a pretty rugged all-metal design, which makes permanent shipping damage unlikely even if the locks are not engaged.

After this cosmetics assessment I looked into the carriage issues that were described to me: I was told that the carriage does not stop at the set-down point after activating START. I plugged in and did a test drive, and indeed the carriage continued running towards the center even with platter absent (in this case the control system comes to the conclusion that a record is present since there is no reflective surface). However, the solenoid engaged at the correct 30 cm point. This immediately told me that the mechanism is working, but that the tracking sensor needs adjustment. Indeed, moving the tonearm to the right with a finger immediately stopped the erratic forward motion. So this will be an easy fix. I also noticed that the arm mechanism is a bit stiff due to hardened lubricants, i.e. this needs some attention to achieve smooth operation.

I also noticed that the DC motor runs a bit rough. This is an indication that it needs some lubrication of its sleeve bearings and a cleaning of the commutator and the brushes.

The bottom line on this Beogram is that it is a nice starting point for a restoration. Nothing abnormal considering the age. I am confident it can be brought back up to specifications.

Beogram 4002 (5513): A New Arrival - A First Look!

Another Beogram 4002 (5513) arrived recently. After an unplanned (yet interesting) delay with the Beogram 4000 that I recently rebuilt, it was time to have a look. I extracted it from the double box where an excellent packing job had prevented any shipping damage. A detailed video about how to do pack a Beogram properly is shown here.

Once I had it out, I took the hood off and had a look at the panels:

They are in very nice condition. The keypad shows the usual triple digit usage pattern indicating not too heavy use:

The STOP key is a bit pulled up, but not too bad. Then I had a look under the hood:

Everything looks quite nice...no obvious signs of 'human intervention' (usually the most challenging  and interesting repairs result from that...;-) and pretty clean. Also the transport lock bushings are still good, so there was no need to put the vacuum cleaner to it. Then it was time to plug it in. I pressed START, and nothing! After checking the fuses, which have corroded holders,

I measured the voltage at the reservoir capacitor, which yielded a healthy >30V reading. After establishing the presence of power, I then determined that P5 had come loose during transport. I plugged it back in and tried again. Now the carriage started limping hesitantly (due to a loose servo belt and hardened lubricants) towards the center of the record. Once it made it to the 30 cm set-down point it properly activated the solenoid, but nothing further happened. Moving the linkages by hand immediately suggested that the lubricants are hardened and that the mechanism needs cleaning and re-lubrication. A first sign of this was the non-parallel tonearm when I had a first look under the hood:

This is usually a sure sign that the arm linkage is stuck. So far so good. It seems mechanically all it needs is a good cleaning and some lubrication to get going again. After this I assembled the panels and put the platter on with the belt to check the platter and arm alignments. As usual the platter sits too low and the arms are not horizontal...this needs to be adjusted.

Other than that the cosmetic condition of this deck is really nice. The hood could use a deep polishing since it has a few deep gashes that can be felt with a fingernail:

One really wonders why people do not put a plastic bag and some foam pad on their Beogram hoods before they store them in their basements. But such is the world. Luckily, there are good polishing materials available these days.

Lastly, I had a look at the MMC20CL cartridge that came with the deck:

The sapphire cantilever and the tip looked pristine and everything appears well-aligned. So I stuck it on the Beogram 4000 that I am re-testing again before shipping, and put Eberhart Weber's "Fluid Rustle" on a pristine ECM pressing that I recently obtained from ebay and cranked up the volume on my Beomaster 6000 4-Channel. Absolutely gorgeous! This cartridge seems to be in pretty good condition!

So, the bottom line is that this is a very good starting point for a happy Beogram 4002 restoration! The deck is in a great cosmetic condition, which is usually the most important concern when it comes to investing money into a restoration. 

Beogram 4000: Replacement of a Stuck RPM Relay with a Modern Encapsulated SMD Relay

The Beogram 4000 that I am currently restoring was not able to switch the AC motor to 45 RPM. After replacing the incandescent light bulbs in the control panel it became clear that, while the 45 RPM button would properly illuminate the 45 trimmer pot, the motor would not change its speed. I traced the signal, and it turned out that the relay was broken. The relay simply switches different resistor networks into the feedback of the Wien oscillator thereby changing its resonance frequency.

The issue with replacing vintage relays is that modern units usually are much smaller and also have a more standardized footprint. This vintage relay actually has an unusual pinout in that the two throws are not mirrored across the relay like in modern units, but are different. The translation between modern and vintage relays was made with a breakout board that matches the pinout of the original relay.

I made a short video about this process. It explains the circuit and gives a demo of the new relay click. This is important in my opinion, due to need to get an audible feedback when pressing one of the RPM buttons. All other buttons give a direct mechanical feedback, i.e. this seemed important. Here is the video:

Here are a couple high res shots of the breakout board. Front:

And back:

This design drops directly into the solder points of the original relay.

Beogram 4000: Restoration of a Seized Solenoid to Tonearm Linkage

It turned out that the linkage that connects solenoid mechanism and tonearm was seized in the Beogram 4000 that I obtained from the UK. This meant I had to take the sensor arm assembly out to extract the linkage that I could relubricate it. It turned out that the pin on which it usually rotates had seized in the linkage and that the pin was liberated from its pressfit socket in the sensor arm base. I made a video that explains the issue and shows how to repair it: