Beomaster 4400 - Australia Project - Wrapping Things Up

This Beomaster 4400 from Australia passed its final bench testing today.

I can also report that musically the Beomaster 4400 sounds great.

Here are a couple of pictures of my first listening tests on the bench.

I will install the Beogram 4400 cabinet cover next.  Then move the receiver to a listening room where I can spend more time checking out all of its features.


Prior to this listening test, I ran my usual harmonic distortion and frequency response tests on the Beomaster 4400.
I use a dummy speaker load of 8 ohms and use a 1 KHz, 0.316 VRMS test input sine wave into the Tape 1 inputs (L & R).

I run the harmonic distortion (THD) and frequency response tests with the Beomaster 4400 at its maximum rated output.  For an 8 ohm speaker that is 50 Watts.  I actually tested it at 55 Watts in this case.

Here are the measurement results.

The signal drop off above 22 KHz on the frequency response measurement is due to the measurement device (QuantAsylum QA401 Audio Analyzer) ending its test run.

The THD measurements at 55 Watts are nicely below the Beomaster 4400 rated value of 0.1%.

Those measurement results are what I have been getting from my Beomaster 4400 restorations so they are good measurements to make and compare to.

To get to this final bit of the Beomaster 4400 restoration testing I spent some extra time installing some power protection features to the receiver.

On all of my Beomaster 4400 restorations I have been installing an arc suppression device to protect the Beomaster 4400 power switch.  The Beomaster 4400 On/Off switch switches full power across its contacts and I have seen one Beomaster 4400 where those contacts were pitted so bad the switch had to be replaced.

My previous Beomaster 4400 restorations were all Type 2419 versions though.  They only required a single arc suppression device.  The following schematic shows the Type 2417 and 2419 power switch differences.

The On/Off switch of the Type 2417 routes both the hot and neutral AC wires to the Beomaster 4400 transformer while on the Type 2419, only one of the AC wires runs through the switch.

On the Type 2419 version I only have to put one arc suppression device across the switch contacts because the two sets of contacts are connected together for the one AC wire they handle.

The Type 2417 uses a set of contacts for both AC wires (hot and neutral) so I added arc suppression on each contact.

Here is my installation of the arc suppression for the Type 2417.  I had to build a 3D printed support to mount them inside the Beomaster 4400 cabinet.  The black mounting screws for the assembly are plastic.

Another power protection install I did was to install a bleeder resistor on each of the two ±35 V rail reservoir capacitors.  The bleeder resistors insure that both 10,000uF capacitors discharge together and relatively evenly when power is turned off.  This also provides a bit of safety when the Beomaster 4400 is opened up for service.  The two 10,000uF capacitors will be at zero volts in that case.

For the bleeder resistors across 10,000uF capacitors 0C8 and 0C9 I chose 5100Ω.

The final power protection installation I did was to build and install a soft start circuit for the ±35 VDC rails.  A lot of amplifiers do this as the soft start circuit slows down the in-rush of current to the reservoir capacitors when power is turned on.  Limiting the in-rush current will put less stress on the transformer, fuses, diode bridge and reservoir capacitors.

The way it works is when the Beomaster 4400 power switch engages, the ±35 V rail voltages go through a pair of 22Ω resistors instead of directly to the 10,000uF capacitors.  That slows down the charging up of those two capacitors.  After about 1.7 seconds, a relay switches out the two 22Ω resistors so the remaining 5 to 10 VDC of rail voltage directly charges up the reservoir capacitors.

Here is a picture that shows the 10,000uF reservoir capacitors charging up with and without the soft start circuit.

A nice side effect of the soft start circuit is that it greatly reduces any "thump" sound through the speakers when the Beomaster 4400 turns on.  However, the reason I added the soft start circuit was for long term protection of the power components.

Here is the soft start circuit installation that I implemented.  I made a small 3D printed mount for the circuit board so I could easily attach it to the inside of the Beomaster 4400 cabinet.

The soft start circuit is powered by the Beomaster 4400 22V power supply.
The inputs to the soft start are the ±35 VDC from the Beomaster 4400 bridge rectifier.
The outputs from the soft start go to the the two 10,000uF capacitors (0C8 and 0C9).

Note: For a Type 2419 Beomaster 4400 I remove the two auxiliary AC plugs that the Type 2417 does not have.  Removing the two AC plugs provides room for the soft start circuit and I created a 3D printed plate to cover the rectangular cabinet cutouts for those plugs.

Now for some more listening to this Beomaster 4400 before packing it for shipment back to Australia.

Beogram 400x DIY Keypad Restoration Kit ... "How-To"

This post discusses a new keypad restoration kit that is now available through DKaudiolover, made by a partner company TangentialLab. The kit is available through the DKaudiolover store and is also used when ordering the DKaudiolover Keypad Restoration Service.

I have restored several dozen keypads over the past few years and have learned a lot in the process. Extracting the original keypad plate (without bending it) and then coating it reliably, without showing signs or wear (in the spots where the original lacquer wore through) and then it not immediately wearing out again is not really possible/reliable/repeatable (I tried!). Getting everything back to the level of quality it was originally can't really be done at the scale of "one keypad" at a time.

I have felt increasingly that given the right set of tools, and the secrets of the procedure, this could be something other restorers and enthusiasts may be able to do. The kit was put together using this experience and includes most of the items that would be difficult to source otherwise. 

Note: If you're doing this yourself, make sure you read this entire post (and the user guide) so you are very familiar with the process before you begin. Some steps involve timing and it's best to know what's coming up.

Today, I have 4 keypads that I'm working on, and I'm going to use the restoration kit for each of them.

This first step is relevant to DC model keypads only. DC (551x/552x) keypads that have "START/STOP" buttons and very sticky glue. AC (550x) keypads have "ON/OFF" buttons and generally don't need to go in the oven. The oven is required to loosen up the sticky glue B&O used on the later models. For earlier keypads, you can usually just press on the back of the keypad and it'll easily pop off the frame, as will the plastic pieces. If your AC keypad does not easily pop off, you can still use the oven method, it works for any keypad, even if it has been previously restored.

According to the guide, the first step is to place the DC keypad inside an oven-safe aluminum container to protect it from heat-cycling during the oven stage. 

Place this container inside a preheated oven at 300ºF/150ºC for about 20 minutes. After this time has passed, use heat-resistant gloves to remove it from the oven. Starting on the back side, use a large flathead screwdriver, placed between two key back pieces and rotated (to apply sideways pressure on both keys); they should break loose. Continue this process until all the backs have been removed, then put the screwdriver underneath the center piece and pry it upwards.

If you have done this quickly, there is a chance that the front side is still hot, if not then you should pop it back (in the container) in the oven for another 5-10 minutes. You don't need to keep the original plastic pieces, we will not be re-using them.

Next use the included x-acto to slide under one of the corners of the keypad plate, then slide across to the other side (front to back or vice-versa, not side-to-side yet). This will give you a gap big enough to fit a metal spatula, I suggest using a paint/spackle spatula.

Slide the spatula towards the center, make sure not to slip as you can easily scratch the frame. When you get to the inside edge of the "45" or "33" keys, you'll have to start rotating the spatula towards the front (so it's pointing towards the back). The center section is the most difficult to get across, so it's best to approach from both the left and right sides before attempting to go across. Trips back to the oven can help keep it warm if you are having trouble. Do not put too much pressure as it could suddenly break free and scratch things up. Near the end of this process, ideally you will be in this position:

Try to slowly lift "up" instead of pushing back, as it could break free and it's best to break upwards and not towards the back.

Next, for both AC and DC models, we need to deal with the old glue that is stuck to the frame. Use the included x-acto to "slide" under the glue as much as possible, try to avoid scratching the metal surface. There is a perfect angle you may find where it easily slides under. You can also "bear down" on the circle in the middle of the blade, this is the best place to put pressure.

Make sure there is no glue left over on the black painted areas, it's better to scratch the paint than to leave the glue.

It's the same process on the back side; you may even decide to start on the back side, since it's a little easier and you can practice getting the right angle and pressure.

Rinse it with warm soap and water, remove all loose glue. Use a melamine pad ("Magic Eraser") to clean the surfaces (don't put too much pressure on the visible areas of the frame as melamine can scratch or remove the lettering). Make sure it's dry before continuing.

Next, use the included paint pen to touch-up the black lines along the edge of the frame. They will have finger marks and potentially a few scratches from removing the glue.

Next, find the small bag with 4 white plastic pieces. These are alignment pieces used to make sure the keypad is centered front-to-back on the frame. They have a special type of adhesive that is "reposition able" and will not damage the frame. Remove the backings and place them at the 4 corners of the frame:

Before proceeding, test out the new keypad plate between these 4 pieces, make sure it fits and get used to centering it horizontally "by feel". I.e. you will feel when the keypad plate and frame are lined up on the sides.

Next, we'll need to remove the backing from the new keypad. It can be a little difficult to lift the corners of the backing, if you have trouble then just put a light diagonal "nick" in the corner and lift one of the side of the nick; it's the best way to remove the backing from this very strong adhesive, I don't usually attempt to get the corner lifted any other way.

The next part is critical. Don't touch the back of the plate in areas where the adhesive is now exposed. Hold the plate by the left and right edges so you can "feel" the horizontal center point with the frame. Don't push down on the keypad until you are satisfied with the centering. You can "nudge" it about 0.2mm side to side when it's lightly resting on the frame.

Note: I don't recommend re-lifting the plate to reposition it; once it's got a strong bond, it won't let go easily. If it's in a really bad spot and you can't nudge it, then just contact us so we can help.

Once you have it in a good place, press down in all the areas where the plate touches the frame.

Next, we will be preparing the black plastic pieces for adhesive. Keep the pieces "all together", do not cut them apart yet. Wipe down all the pieces to remove excess dye (there could be a lot!) and oils from the surfaces where we will be applying adhesive. Don't waste the wipe on areas that won't have adhesive, focus only on the front side.

Once the pieces are clean, wear gloves and be in a well-ventilated area. Wipe all the cleaned front sides (in the areas that will have adhesive) using the adhesive promoter. Remove gloves and wait for the promoter to dry.

Start applying the adhesive to each piece, making sure it is centered (the small pieces of adhesive are slightly larger than the key backs). Press down on the entire surface of each piece, and the edges of the small pieces (so the bond is edge-to-edge). Try to avoid air bubbles; if you get one, you can try to put a hole or two in it using a blade and carefully push the air out as much as possible.

Bend the pieces back and forth a few times to weaken the connections and cut them off (using a blade or wire cutters). Trim the sprue's so the edges are completely flat in the previous connection areas.

Note: The two upper back pieces, used for 33/45 keys, ARE DIFFERENT from the other key backs. Make sure not to mix them up! They are dimensionally unique, optimized for a tiny slope the keypad has.

Next, put a nick in the corner of each piece and peel the backing off. Below you can see where I nicked the center piece before peeling it off:

Last step is placing all the pieces into the keypad frame. Start with the center piece. Next, align each key back piece with the center of the key, about 1mm away from the center piece. You can drop the key backs in lightly and then position them with the chisel blade before pressing down too hard.

And that's it, we're finished restoring the keypad.

Actually, I did 4 of them this time:

Beogram 8002: A New Arrival from Missouri - First Impressions

I recently received a Beogram 8002 from a customer in Missouri for restoration. The unit arrived safely packaged in a Beolover double boxed shipping container. I extracted it from the packaging and put it on the bench:

The unit is in decent condition except for a very scratched hood. This could be fixed by installing a new reproduction hood and transferring the original aluminum trim.

The aluminum surfaces are pretty good:

The otherwise nice platter has some damage in the center:

The veneered side panels have the usual chipped corner areas:

I removed the black panel under the arms and found a detached metal shield due to degraded double sided tape:

Like in most Beogram 8002, the main aluminum panel was also loose and came off after removing the tape that held it in place for shipping:

I opened it up to extract the functional parts:

This shows them on my Lazy Susan on the bench:

After making sure everything was put together again correctly, I plugged it in. After pressing start it came alive and moved the carriage a few mm. After the brief motion, the carriage immediately returned home and the deck shut off. Most likely this points to an issue in the << >> keys setup in the keypad.

Let the fun begin!..;-).

Beogram 4002 (5503): Arm Does Not Drop Anymore - Repair of Broken Solenoid Switch

A fully restored Beogram 4002 (Type 5503 with AC platter motor) that I sold in April 2025 to a customer in California recently had to return to the bench due to a warranty call (all Beolover-restored B&O comes with a one year warranty that covers all functional issues that may arise): After pressing ON the arm would find the LP setdown point, but it would not drop. It just sat there silently over the spinning record.

I put the unit on the bench and had a look. It quickly became clear to me that the solenoid did not get enough power to strike. Since I was able to push the solenoid lever down and it would then hold I immediately suspected the solenoid switch. This switch connects the emitter of the solenoid transistor (0TR4) to ground during the initial activation of the solenoid. When the solenoid plunger is fully extended the solenoid arm hits the switch and disconnects the emitter from ground, forcing the current to flow through the 8 Ohm solenoid resistor 4R1 (located on the PCB under the carriage). This reduces the current in the coil that it does not overheat. In this case the switch was oxidized and did not make its initial ground connection. Hence the solenoid only received the 'hold current' through the resistor and therefore did not have enough force to overcome the force of the release spring and friction etc...

This picture shows the small PCB that sits to the left of the solenoid, which holds this switch:

The switch is under the wiring. After unsoldering the three wires that connect the board and removing/loosening the two screws it can be removed:

I replaced the switch with a new one:

It is generally not a good idea to just sand the contacts a bit when this switch fails. While it can restore function for a while it usually does not last. The reason for the switch failure is that the oxidation preventing coating of the contacts burns off after a sufficient number of activations due to arcing. Therefore, the contacts quickly re-oxidize when they are sanded and it fails again. This switch carries about 3-4 amps during solenoid activation and breaking this current can cause small arcs. This is probably the reason why B&O replaced this switch with a timed electronic current limiter in the later DC motor 4002s and the 4004.

After reinstalling the board everything worked normally again. I played a couple records without a hitch, i.e. this Beogram 4002 is ready to return to its owner.