This post discusses the full restoration of a Beogram 4004 (Type 5526) that I recently received from a customer in California. My initial assessment of the unit is posted here. My customer decided to get a few upgrades along with the full restoration: This Beogram received a Beolover Commander remote control system, an internal Beolover RIAA pre-amplifier, and the Beolover carriage motor for quieter mechanical operation.
This shows the unit in its final restored condition:
Beolovely! Let's see what it took to get there:
This shows the unit on the bench as received:
As usual, I decided to do the DC platter motor first. They pretty much all need their shaft bearings replenished with oil. Most DC motor Beogram 4002 and 4004 have dry bearings. The infusion process under cacuum takes 2-3 days and so it is a good idea to get this going first!
This shows the extracted motor:
I removed the outer enclosure and found this:
Clear evidence that the Beolover had been in there already! I usually mark the bearing position before I remove it so I can install it in the same orientation after the oil infusion!
I have probably restored about 200 of these motors by now, and so I had forgotten that I had already received this motor in 2020 for repair! See here for the report on my work on this motor. It came out very well.
After restoring the unit, I re-did my 24 hrs RPM test (see below) and found that the motor still ran as well as it did after my restoration. This is welcome news, as it suggests the oil re-infusion is a long-term solution for these motors.
After this little excursion down memory lane, I proceeded to restore the mechanical systems on the carriage. I removed all the old lubricant-encrusted moving parts for the ultrasonic cleaner.
This shows the liberated carriage with all the parts removed:
It is a good idea to rest it on a foam pad or similar to protect the fine wiring on its bottom side.
One important step of any restoration is de-magnetizing the arm-lowering solenoid. Their pistons are often magnetized, which can cause them to stick. This has the consequence that the arm-raising can be a bit delayed after the electronic signal arrives. This issue is often responsible when the needle drags across the platter during autoreturn at the end of a record.
This shows the extracted solenoid:
I removed the plunger:
I usually test the magnetization with a small M3 iron set screw (if you try this at home, don't use a stainless type - stainless steel is usually only weakly paramagnetic). Like most solenoids that I open up, this one also had a plunger that was able to attract my set screw!:
This meant it needed de-magnetization! After treating it with my tapehead de-magnetizer for a little while, it did not attract the set screw anymore:
All good again in the solenoid department!
In the meantime, the other parts came back cleaned from the ultrasonic:
Beoshiny!! I started putting the carriage mechanics back together. The first step is usually installing a fresh damper gasket.
This is an important task since the original gaskets are often hardened and/or deformed. This can result in inconsistent arm-lowering speeds. It can be pretty hair-raising when the newly restored $700 cartridge from tonabnehmerservice.de crashes down on the platter without any damping!...;-)
This Beogram presented a new challenge for me: Someone had damaged the threads of the tapped holes for the screws that hold the carriage rods in place. So I got my tap and die set out and re-cut them with an M3 tap.
After putting the moving parts back together, I installed the new Beolover carriage motor upgrade. This shows the motor assembly opened up. The vibration-damping foam of the original motor had degraded, like I find it in many Beograms of this vintage:
I put in the new motor. It comes with EPDM rubber rings for vibration damping. This will last much longer than the original foam.
This shows the new motor installed together with the new Beolover Aluminum Carriage Pulley for Beogram 4002 and 4004:
This shows the entire rebuilt setup back together:
I moved on to clean and re-lubricate the pivot point of the damper-to-arm linkage. It is located between the sensor and tonearm assemblies. You can see it stick out from the V-cut in the small metal arm attached to the back of the arm counterweight:
I removed the sensor arm assembly and took out the linkage:
I cleaned and lubricated the pivot point and reinstalled the linkage. Of course, the small copper plate that helps ease the lateral arm movement when the arm is up had come loose after I tugged at it with my tweezers. The little plates are attached with double-sided tape, which, after almost 50 years, is usually degraded.
I glued it back into place with a dab of epoxy:
This shows everything back together:
The final task of the carriage restoration was replacing the tracking sensor light bulb with a Beolover Tracking Sensor LED Light Source (Beogram 4002 and 4004). This shows the original setup with the black bulb housing still installed:
I removed the housing, which revealed the tracking sensor aperture:
This shows the original part and the Beolover replacement in direct comparison:
The small SMD LED is in the approximate location of the original bulb filament. This makes the LED conversion a simple drop-in replacement. This shows the new part installed:
I moved on to rebuilding the PCBs. First came the main PCB. It has two power Darlingtons installed on its solder side. It is best to replace them first with the board still installed. This makes it straightforward to place the new ones in the exact same position as the originals. This shows the original 1IC1, which regulates the 21V rail:
The original is usually a TIP120. I normally replace it with a TIP102, its stronger cousin.
After also replacing 1IC4 with a TIP107, I removed the board and flipped it around. This shows it in its original condition:
Here is a detail shot of the RPM section, consisting of a Panasonic relay and the two trimmers to its left for setting the platter speed:
I replaced all electrolytic capacitors, power transistors, RPM relay, and the record sensor transistor with new parts. The RPM trimmers were replaced with modern 25-turn encapsulated trimmers. This shows the rebuilt board and the extracted parts:
Here is a detail shot of the RPM section with the new relay and trimmers:
After doing this board, I removed the RPM panel above the keypad. This shows it flipped over, revealing its two bulb covers:
After prying off the two covers with a suitable screwdriver, the bulbs can be accessed:
The two small PCBs in front of the assembly are the Beolover RPM Panel LED Backlights for Beogram 4002 and 4004 (Types 551x/552x).
I removed the bulbs and soldered the LED boards in place.
They solder directly to the solder points where the bulbs' wires were connected.
With the RPM panel out of the way, it was easy to remove the single screw that holds the keypad cluster in place and take the keypad out. This allowed access to the output PCB, which is shown here in its original condition:
The front part of this PCB is identical to the 4002 output board, containing the output relay and its delay circuit.
The additional circuitry on the 4004 board is devoted to the remote control functionality that allows control via a Beomaster 2400. I replaced all the electrolytic capacitors and the output relay.
This shows a detail photo of the replaced output relay and rebuilt delay circuit:
The added small red switch in front of the socket for the output cable allows connecting the signal and system grounds. This can be helpful if there is a humming issue when connecting the Beogram to a receiver.
I moved on to replace the 4th and final incandescent light bulb in this Beogram. It was located in the sensor arm and is crucial for the record detection system. This shows the small back compartment from the front of the sensor arm pulled out:
The parts next to the arm are the Beolover Sensor Arm LED Light Source (Beogram 4002, 4004, and 4000) and its alignment aid.
This shows the bulb removed and the LED board installed:
At this point, everything had been removed from the enclosure except the floating chassis itself. I opened the transport locks up so I could extract the chassis. This shows one of the completely degraded transport lock bushings:
Most Beograms of this vintage have this issue. I usually replace the bushings with a new set of Beolover Transport Lock Bushing Set for Beogram 4000, 4002, and 4004:
Each bushing comes in two parts, which makes it very easy to install them. Simply push one half into the bottom.
and the other from the top:
I usually put a small bead of super glue on the vertical parts of the bushing halves to secure them in place. Some Beograms have slightly larger holes for the bushings, and the glue helps hold things together.
Next, I removed the old reservoir capacitor:
I also removed the wood frame from the enclosure. Like many of the original frames, this one was a bit warped:
It is possible to bend the sides back straight with carpenter’s clamps and pieces of wood:
After 2-3 days, the bends are usually straightened out. It is important to get the frame sides as straight as possible, since otherwise it can be difficult to seat the aluminum panels properly on the Beogram.
If you try this at home, do not overtighten the clamps, or the wood may break.
At this point, the enclosure was empty save for the many transport lock bushing fragments strewn around:
I vacuumed the enclosure clean and wiped it down with a wet paper towel.
Time to put things back together! I started with the floating chassis. This shows one of the new transport lock bushings with its lock screw in the center:
At this point, I remembered to check the fuses. They are often damaged, with their metal end cups coming off the glass cylinder. I removed them:
They were both ok with their cups firmly attached:
I put them back in and focused on installing a new Beolover Main Reservoir Capacitor for Beogram 4002 and 4004 (Types 551x/552x):
Since this Beogram only used a single capacitance reservoir capacitor, all I had to do was tack on the white and black wires from the power plug of the main PCB.
I put the remaining components back in and fired the deck up to adjust the bias of 1TR3 (the sensor arm transistor) to get 4V at its collector. This needs to be done while the board is installed. So I solder the trimmer first to the solder side that I can access it for adjustment when the deck is powered up.
After adjusting the trimmer, I moved it over to the component side. Then it was time to check if the record sensor worked properly. I connected my oscilloscope between the collector of 1TR3 and ground and installed the platter. This is the trace I measured while spinning the platter with a finger with the sensor arm positioned over the platter:
Each of the dips represents a platter rib passing under the sensor. I measured an amplitude of about 6.5V, which is a nice, stable sensor signal.
My next task was doing the arm adjustments: First came parallelism. Both the sensor arm base and the sensor arm need to be perpendicular to the carriage rods, and the tone arm needs to be parallel to the sensor arm with a spacing of about 7mm. To get this often tedious adjustment right, I now use my recently developed Beolover Arm Alignment Tool for Beogram 4000, 4002 and 4004:
I installed the wood plinth that by now had fairly straight side pieces, and then I started the process of aligning arms, platter, and floating chassis to get the platter parallel to the arms across their travel, and the platter flush with the surrounding aluminum panels. This can be an iterative process that takes a few passes to yield proper alignment.
Once everything was perfectly aligned, I replaced the flimsy circlip that holds the counterweight screw in place
with a M3 square nut and a washer:
This allows me to lock my calibration in place so it survives shipping the Beogram. Then I adjusted the arm-lowering limit:
This important adjustment helps prevent needle damage if the arm should ever be lowered onto an empty spinning platter due to a malfunction of the record detection circuit.
Next came the calibration of the tracking force. I usually adjust the counterweight so that the little scale on the adjustment wheel is accurate around the standard 1.2g tracking force that most B&O cartridges prefer.
In general, I recommend checking the tracking force once in a while with a small digital gauge like the one I use in the above picture. The adjustment wheel on the arm assembly is notorious for not being all that precise.
After these adjustments I installed my BeoloverRPM device to characterize the performance of the DC platter motor:
The BeoloverRPM has two operational modes. In 'slow' mode (shown above), it measures the RPM in 10-second intervals and sends the data to a serial port of a computer, where it can be recorded with any generic terminal software. This allows plotting the RPM over long periods of time using Excel or similar software. This shows the result of my 24 hrs measurement:
This is quite a nice result for any Beogram DC platter motor! As good as it gets! The curve looks pretty much the same as what I measured in 2020 when I originally restored this motor! This suggests that my oil-infusion process is long-term stable!
Next, I collected some high-resolution data in the 'fast' mode of the BeoloverRPM:
In this mode, the device sends an RPM measurement every time a platter rib passes through underneath the sensor. This gives 24 RPM measurements per platter turn (there are 24 ribs). This allows visualizing short-term RPM changes caused by the feedback-based motor control circuitry. This graph contains the data covering ~35 platter turns (~70 sec):
The prominent zig-zag pattern is a measurement artifact that comes from the fact that the spacing of the platter ribs around the platter is slightly irregular due to manufacturing imperfections. This generates a repeating pattern for every platter turn (sort of a 'platter fingerprint'), which is superimposed on the real RPM changes that are introduced by the feedback system that keeps the motor RPM stable over time. This real RPM change is essentially the sine-wave-like pattern that modulates the zig-zag pattern. An evaluation of the wavy component yields a wow and flutter estimate of about 0.1%.
This is 2x of the 0.05% stated in the specs list in the service manual. This difference is most likely systematic due to the entirely different way wow and flutter were measured in the 1970s when these turntables were produced. I see it for all Beogram motors that I restore. Back then, the measurement was carried out with a test tone on a test record. In these measurements, deviations from the tone center were measured with an analog spectrum analyzer and then converted into a wow and flutter number. It should be pointed out that this discussion is pretty academic in the first place since humans typically start recognizing frequency fluctuations above the 0.7% threshold, i.e., the RPM fluctuations of this Beogram are well below this threshold, whether the number is 0.05% or 0.1%. This motor is definitely ready for duty!
After this measurements completed, I replaced the original oxidized DIN plug.
with a new all-metal type that has nice gold-plated contact terminals:
On to the upgrades: First, I replaced the original output PCB with a Beolover Internal RIAA Pre-Amplifier for Beogram 4002 and 4004. It is a direct plug-and-play replacement for the original board.
This shows it installed:
The on-board RIAA pre-amp allows directly plugging the Beogram into any modern high-level input on current B&O or Sonos speakers, etc., or into an amplifier without a phono input through a CD, DVD, or AUX input.
With the RIAA in place, it was the perfect moment to install the Beolover Commander Remote Control for Beogram 4002 and 4004. It is also a plug-and-play installation. The first step is plugging the Commander board into the keypad jack on the main PCB:
Since this is a 4004, the Commander gets its power from the output board. This requires the installation of the white 4-wire harness that connects the Commander board to the RIAA board. The Beolover RIAA already has the appropriate Commander jack broken out, so the normal Commander adapter for the keypad connector does not need to be used. I stuck it into the keypad jack of the original output PCB in case this Beogram will ever be used with the original output setup:
Next came the installation of the keypad. This was the moment for swapping out the smudgy original keypad with a newly rebuilt one. This shows old and new in direct comparison:
See here if you are interested in fixing or getting your keypad fixed. A new keypad is a great way to significantly increase the cosmetic appeal of a Beogram!
The original keypad also had broken-out plastic fixtures that hold the RPM panel in place:
Luckily, there are faithful reproductions of these plastic parts available from the DKsoundpartsstore in Denmark:
All that needs to be done for implementing them is transferring the metal springs over from the original ones:
This shows a new one installed on the rebuilt keypad
Then it was time to plug the new keypad in. This shows how the grey keypad plug goes into the jack on the RIAA board:
The black main plug of the keypad goes into the jack on the Commander board. This shows everything in place:
And then it was finally time for a test spin with this beautifully restored Beogram 4004!
I selected one of my favorite Eddie Henderson records, "Mahal", which he released in 1978 on Capitol Records (SW-11846). Herbie Hancock and Hubert Laws are among the players. A very interesting record in my opinion! Here is an impression of this lovely album playing on the restored Beogram!
Beautiful! I will now play this Beogram for a couple of weeks to see if there are any intermittent issues, etc.
There was one more task to be done: Replacing the scratched hood with a new reproduction hood and aluminum trim.
The first step is removing the original hood from the metal hinge assembly. I detached the aluminum trim on both sides using a razor blade:
The hood can be removed after the two screws are removed on both sides.
It turns out that this hood was close to cracking off the hinge anyway. The typical stress fractures were already well-developed near the bolt holes:
The first step for installing a new hood is always checking if there is an interference between the plastic and the metal hinge bar. If the plastic chafes on the metal, it can cause the hood to crack off the hinges. Therefore, I bolt the hood to the hinge for a test before I go ahead with the installation, and then manually work the hinge while watching if there is any touching. The problem usually occurs close to the hinges as indicated below with the red frame:
This hood demonstrated a safe minimum distance of about 1 mm across its range of motion.
After this successful test, I went ahead and glued small 3D printed plastic bits into the strange 'channels' they designed into the sides of the hood where the aluminum trim goes:
After the epoxy hardened, I trimmed the plastic bit with a razor blade to smoothly continue the corner in the plexiglass:
The purpose of the plastic bits is to help make a sharp bend in the aluminum trim around the corner. The 'channel' causes a void at the edge under the aluminum, which makes it difficult to make a good bend.
Then it was time to center the new aluminum trim. I used my 3D printed alignment pieces and a stretch of blue tape
to make an alignment pencil mark:
Then I bolted the hinge assembly back into the hood. I usually put a bit of white wood glue on the threads so the screws stay put. One cannot tighten them very much. Too-tight screws can also cause a premature cracking of the hinge areas of the plexiglass.
The next step was attaching the new aluminum trim and then making the bends down the sides using my bending block.
Beolovely!:
The final touch was installing the rubber bumpers into the holes on the front corners of the hood:
The provided bumpers have stems that are a bit too short in my opinion and they can fall out fairly easily. For this reason I usually put a bit of superglue gel into the holes before I put the bumpers in.
This completed my work on this Beogram 4004!
Here are a few nice pictures of this fully restored Beogram 4004. Enjoy!
