Beogram 4000: Carriage Returns Home Immediately After Setting Down on the Record

Oh well, the Beogram 4000 that I restored in January 2025 came back to my bench exhibiting an issue I had not experienced before:

After pressing ON the carriage went and found the LP setdown point and put the arm down. Immediately after hitting the run in groove, the carriage returned home with the arm down. It did that at a fairly high speed. Once home the unit shut off and the arm lifted.

Since the << and >> buttons worked fine with the arm up, a problem with the H-bridge was unlikely. This meant there must be an issue with the tracking sensor.

The Beogram 4000 features two photoresistors FC1 and FC2 that control the reverse and forward directions of the carriage motor (later 4002/4 models are differently set up, with only one photoresistor for the forward direction). This means the dual photoresistor tracking sensor can control the carriage in both directions, forward and reverse. The carriage is at rest when the forward and backward currents through the H-bridge (i.e. the motor) just cancel out. This condition is reached when the aperture in the tracking sensor illuminates both photoresistors with the same intensity, i.e. when it is positioned just between the photoresistors. If everything is properly adjusted, this condition coincides with the tonearm being parallel to the sensor arm. As the arm gets pulled towards the record center during play the arm gets deflected laterally, which causes the forward current to become larger than the reverse current, and the carriage starts moving forward, following the motion of the arm.

A consequence of this setup is that if one photoresistor circuit is not working properly, the carriage motor will already see a significant current even with the tonearm in parallel alignment, and the carriage will start moving. If the failed photoresistor circuit is the one that controls the forward motion, the carriage will always go reverse, independent of the lateral deflection of the tonearm.

With this in mind, I started examining the forward direction circuit. A good rule of thumb with the Beogram 4000 is that 90% of its issues are typically caused by bad contact terminals in the many switches, or by a wiring problem. The Beogram 4000 is an early 1970s design, when wire-to-board connections were still hardwired (instead of using modern wire-to-board headers and plugs, which are mechanically much more resilient). These soldered wires have a tendency to break off at the solder terminals when the Beogram is handled or transported.

This personal 'statistic' was confirmed in this unit: When I had a closer look at the wiring I immediately found the problem. The wire connecting the forward photoresistor FC2 to the H-bridge was broken off at its terminal on the main PCB (yellow marking in the photo):

I cleaned wire end up and soldered it back to the terminal. And the deck was operating normally again! I will play this Beogram a bit and then it should be time for sending it back to its owner in Australia!

Beogram 4002 (5503): Installation of a New Hood, Restored Keypad, New Carriage Motor and the Commander Remote Control System

This post describes the additional installation of upgrades and the performance of cosmetic restorations on the Beogram 4002 (Type 5503) that I functionally restored in August.

Like many Beograms at this point in time this unit had a fairly badly scratched hood. This shows the original hood

and some of its scratches:

My customer elected having a new reproduction hood from DKsoundparts installed instead of getting the original hood polished. I like these hoods a lot. They are crystal clear and a perfect copy of the original ones. They even improved the design of the bolt holes for the attachment to the hinge, which should make cracking much less likely. Therefore, replacement is a much better option than polishing.

The installation requires removal of the original hood from the metal hinge part. The screws responsible for the attachment can be fund under the vertical parts of the aluminum trim that is glued to the back end of the hoods. The original trim can in most cases be removed by pushing a razor blade in-between the trim and the plexiglass:

After removal of the two screws on either side the hinge part is liberated. This shows the hinge together with the new hood and a new aluminum trip strip (the original trim usually gets damaged/wiggly when trying to remove it from the original hood):

Before the hood can be bolted to the hinge it is a good idea figuring out the alignment of the trim. It needs to be installed exactly centered that the two parts that get bent down at the sides are exactly of same length. For doing this I use 3D printed alignment pieces that can be attached to both sides of the hood. Their 'wings' make it easy placing the strip exactly centered:

I use a strip of blue tape attached to the hood and a pencil to make a mark once the centered positon has been determined:

This mark is used to place the strip after the hinge has been bolted in. Bolting it in is easily done with a suitable Philips screwdriver:

This shows the hood after putting the new strip on it:

This hood is ready for installation!

The next step was the implementation of the Beolover Commander Remote Control for Beogram 4002 (Type 550x with AC Platter Motor). The Commander uses an Apple Remote for controlling all functions of a Beogram. The Commander even ads autorepeat functionality similar to what B&O implemented in the later Beogram 8000/8002 models. A special function of the AC version of the Commander is that it ads a record swiping function like in the later DC motor Beogram models. Simply press the center button on the Apple Remote while the deck is off, and the platter motor will come alive as long as the button is pressed.

Unlike the plug-and-play version for DC motor Beograms, the installation of the AC Commander requires a small amount of soldering due to the hardwired nature of the board to board connections in the 550x Beogram Types.

The first step is the removal of the keypad from the keypad PCB:

Note that the shown keypad is not the original one that came with this Beogram, but a temporary replacement from my stash that allowed me working on the unit, while I waited for the refurbished keypad to arrive. Keypad restorations are available via the Beolover's DKaudiolover.com store.

This picture shows the area of the keypad PCB where the wire harness is attached to the board:

The installation of the Commander hardware requires soldering a wiring adapter onto the PCB that allows the Commander to communicate with the Beogram control circuitry. For this purpose an area of the solder pads needs to be cleared from solder in order to generate a 'landing zone' for the adapter board. This shows the zone cleared after using my Hakko de-solder pump on it:

Once the zone has been cleared, the adapter can be soldered to the board:

It is important to put the adapter in that the white jack is flush with the board edge. Otherwise, there will be an interference between the adapter and the keypad assembly in some Beogram versions when the board is pushed back into the keypad after installation. This shows the Commander board bolted piggyback ontop of the main board and the white wiring harness already plugged into the adapter jack:

The next step was pushing the keypad PCB back into the new refurbished keypad:

This shows the smudgy condition of the original keypad for comparison:

Original keypads often show such patterns. They represent damage to the clear coat that gives the pads their unique sheen. Over time the coating material deteriorates due to the contact with the oils and acids in the skin and mechanical abrasion. Our restoration process is discussed here.

The next step was bolting the auto-repeat indicator of the Commander onto the keypad assembly under the standard mounting screw:

Then it was time for plugging the white wiring harness into the corresponding jack on the Commander board:

This concluded the installation of the Commander module.

My customer also wanted the original carriage motor upgraded with the new Beolover Carriage Motor for Beogram 4000, 4002, and 4004. While there was nothing wrong with the original motor, the Beolover replacement offers lower noise, fewer vibrations and lower current draw when the motor runs. Therefore, it is an interesting improvement for those who want the best possible performance of their Beogram. This shows the original motor still installed:

Four screws and two solder points later the motor assembly was extracted:

I removed the top, which revealed the motor:

I exchanged it with the new Beolover motor:

It is a good idea feeding the leads through the small window in the bottom part of the housing.

Then I bolted the assembly back in and soldered the leads to the carriage board:

This concluded my upgrade and cosmetic work on this Beogram and it was time for another test run. The Commander remote control worked flawlessly and the new carriage motor yielded a noticeably quieter carriage motion during start!

This shows the completed Beogram playing one of my recently acquired Blue Note re-issues, Donald Byrd's album "Stepping into Tomorrow" which he released in 1975:

What a lovely contemporary combination!

Here a detail shot of the pristine new keypad!

This Beogram is now in a near-new condition with improved functionality and performance! Very beolovely! I will play it a bit more and then it will be time to send it back to its owner in Ontario!