Beomaster 1900 Type 2904: Assessment of a New Beomaster Restoration Project

Here is the start of a new Beomaster 1900 restoration project. 

This Beomaster unit has been patiently waiting for me to retool my workshop for Beomaster restorations after a lengthy stint of Beogram restorations and repairs.

I have several different Beomaster units in my backlog at the moment and it is time to start getting them working again.

So here is the first look at the latest Beomaster 1900.

The Beomaster 1900 is in really nice cosmetic shape.  I would rate it excellent except that it is suffering from a common problem with these models.  The thin veneer trim is separating from the plastic side panels the trim is mounted to.  I have seen this before with the Beomaster 1900 and 2400 receivers.

The plastic side panels and single, front panel do remove from the cabinet though.  Removing them (carefully so as not to break their mounting tabs) will make it easier to fix/reattach the veneer.

I moved on to the disassembly of the Beomaster so I can prepare it for replacing the electrolytic capacitors inside.  There are quite a few electrolytic capacitors to replace.  Around seventy.

I started removing the panels of the Beomaster 1900 first.

This photo shows the control panel (with the touch buttons) and the front, plastic trim piece removed.

The next four photos show removing the Bass, Treble and Balance indicator masks from the slide controls so the control panel PCB can be removed.

I was happy to see that the indicator masks were is great shape and the slide controls appear to be intact and working.

Two press-to-fit connectors are all that connect the control panel PCB to the rest of the Beomaster components.  I disconnected those and removed the control panel PCB.

With the control panel PCB out of the way I continued on and removed the indicator panels (the volume indicator, the Bass, Treble and Balance indicators and the source selection indicators).

Here is the volume indicator panel being removed.

Here is the indicator panel for the Bass, Treble and Balance being removed.

Finally, here is the source selection indicator panel shown already removed.

Here are the two plastic side panel (trim pieces) removed.

In order to free up the main PCB I removed the four output amplifier transistor heat sink assemblies.

I cleaned off all of the old white thermal paste from the transistors and heat sinks.
I will be replacing the thermal paste with SIL-Pads.

The Beomaster 1900 is now in a position where I can access all of the electrical components I need to access in order to start replacing old capacitors.  A while back I started making the parts for a jig to support the disassembled Beomaster 1900/2400 structure.  I used the pieces I have completed so far to put the Beomaster 1900 into a service position for working on.

Beogram 4004 Type 5526: Starting in on the restoration work - Part 1

Since the last post I have jumped into the Beogram 4004 restoration tasks.
I am going to show the before and after pictures of the PCB 1 and PCB 8 capacitor replacements but I am also going to show a few other tasks that I performed along the way.

Before tackling the PCB 1 and PCB 8 part replacements I wanted to get the problem of the End Switch (ES) and Switch On/Off (SO) switches resolved.

The previous post showed the broken ES switch.  I decided to replace both the ES and SO switches with a good set from a spare Beogram 4002 Type 5513 unit.

Here are a couple of before photos -

Here are the two replacement switches installed -

While I had the Beogram 4004 floating chassis components in front of me I continued by disassembling components I am going to replace or restore.

Next, I removed the servo motor and the tangential drive spindle/pulley assembly.

Here is the servo motor opened up.
The foam padding is still intact but pretty brittle. It will eventually completely dry out and start breaking into pieces so I will replace it with new vibration damping material.

I cleaned the spindle with a brush and some alcohol. 
I removed the original, plastic pulley from the spindle and installed an aluminum pulley.

Next, I removed the original tracking sensor lamp assembly to prepare for the installation of the replacement Beolover Beogram 400x tracking sensor lamp assembly.

With the tangential drive spindle removed the tangential arm assembly can easily be slid up and down the two guide rails.  This is a good time to clean them before applying new grease.

That is all I am going to do on the floating chassis components for now.
It is time to move on to the work on PCB 1 and PCB 8.
Once those are complete I will return to the floating chassis to install the new Beolover tracking sensor lamp assembly along with replacing the fixed arm, record detection lamp (also a Beolover lamp assembly).

Here is the before photo of the Beogram 4004 Type 5526 PCB 1, the main turntable electronic control circuits.

Here is the PCB 1 after photo...after the capacitor replacement has been done, a new platter speed selection relay has been installed, new trimmers for the platter speed control, new trimmer for the position sensor calibration (1R88), new 1TR3 transistor for the record detection circuit and a corresponding 2MΩ trimmer for calibrating it (in place of the original 1MΩ, 1R26).

Note: As we normally do, the 2MΩ, 1R26 trimmer is installed temporarily on the trace side of PCB 1 so it is accessible when it is initially set (to calibrate 1TR3).  Once the calibration is done, the 1R26 trimmer will be moved to the component side of PCB 1.  You can also see that a WIMA 4.7uF capacitor has been located on the trace side of PCB 1.  That component will stay on the trace side as I don't want any possibility of it physically interfering with the floating chassis mount that sits below PBC 1.
Regarding transistor 1TR3...the original transistor measured with an Hfe below 500 so I installed a new transistor that has an Hfe of above 500.  Together with the 1R26, 2MΩ trimmer there should be no problem adjusting the record detection signal per the service manual.

I also worked on the Beogram 4004 Output circuit board (PCB 8).
The Beogram 4004 Output circuit board has a lot more components than a Beogram 4002 from the same time period (i.e. a Beogram 4002 Type 5523).  The reason for that is the Beogram 4004 has a remote control circuit that ties in with a Beomaster 2400 receiver.  

Here is the before photo of the PCB 8 board.

Here is the after photo.

Things to note on the updated board are the replacement of the muting relay and the addition of a grounding selection switch.

We install this type of switch on all of our Beogram 400x turntable restorations to provide an easily accessible control over the way the signal ground and chassis ground are configured inside the Beogram for the phono cable.  Some phono amplifiers need signal ground and chassis ground tied together or else there is hum on the phono signal.  Other phono amplifiers do not.  The switch makes both options available for the owner.

The project is getting close to actual record play now.

In the next post I will install the new Beolover Fixed Arm Lamp Assembly,  the Beolover Tracking Sensor Lamp Assembly, lubricate the tangential arm assembly and perform the service manual tonearm adjustments.

Beogram 4004 Type 5526: A Local Beogram 4004 Project Continues (Finally)

It is time to get cracking on a delayed Beogram 4004 project.
I initially assessed this Beogram 4004 back on this January 2022 post.
A bunch of delays ensued but now things can get moving again.

I disassembled the Beogram 4004 to begin work on the various components.

Here is the PCB  1 board shown with its four mounting screws highlighted.

Here is PCB 1 removed.  The main circuit board, PCB 1, looks in great condition so I will start on the restoration of this board in the next post.

Next in line for the disassembly is the Beogram keypad.
This keypad is in really nice shape for an original keypad. There are some minor scuffs and with the light held just right, you can see some signs of where fingers operated the controls.

The underside of the keypad shows the typical tarnished button contacts. I will clean those thoroughly and coat them with some Deoxit contact cleaner.

With the keypad removed I can get to the Beogram 4004 Output/Remote Control board (PCB 8).
The PCB 8 board contains the phono mute relay and is where the audio signal transitions from the tangential arm assembly chassis to the phono cable that carries the audio signal to an external preamp.

Here is PCB 8 from this Beogram 4004 unit.

PCB 8 is a board that is in all Beogram 4002/4004 turntables. All of the types have the Phono Audio Output and Mute circuit.  The rest of the PCB 8 board is for additional circuits that various Beogram 400x types can have.

For example, the Beogram 6000 has 4-Channel decoding circuitry on its Output Board.
The Beogram 4002 Type 5523 only has the muting circuit and nothing else.
This Beogram 4004 has a remote control circuit that integrates with the remote control of the Beomaster 2400 receiver.  Of course nowadays we have the Beolover Commander Remote Control. :-)

After PCB 1, PCB 8 and the control keypad components are out of the way, the Beogram 4004 floating chassis can be removed from the cabinet base.

This photo shows a section of the cabinet with one of the lockdown mechanisms for the floating chassis.  There are three of these lockdown mechanisms and each one must be disassembled to remove the floating chassis.  The original Beogram 4004 would have had rubbery, plastic bushings around the lockdown plates.  As is very common, the original bushings became hard and brittle...to the point where they just broke into pieces.

The following photos show the disassembly of the top part of the floating chassis lockdown mechanism.  

This picture shows a lone piece of the original lockdown bushing.  That is where the bushing was located before it deteriorated and broke apart.

Here is the lockdown mechanism after the floating chassis has been removed.

Here is the removed Beogram 4004 floating chassis assembly.
Highlighted in the photo is the actuator of the Beogram ES switch. It was floating around in the cabinet.

The tonearm assembly looks really great on this Beogram 4004 unit. The arm lowering works nice and the components look to be aligned properly.

The servo motor and pulley look okay and do function.
The original plastic pulley is in good shape but does have the start of a small crack.
The internal vibration damping material of the servo motor is showing signs of age. The foam material eventually crumbles and becomes dust.

Here is a picture of the SO and ES switches of the Beogram tangential arm assembly.
The ES switch is broken and the SO switch looks pretty worn too.

Here is what two intact SO and ES switches should look like.

I will have to find a couple of replacement switches for the ES and SO switch.

Last, here is a look at the tonearm assembly lowering and raising mechanism.  It is in great shape as I mentioned earlier.

After this Beogram disassembly I can update my assessment of the restoration.

The recapping and replacing of components on the circuit boards doesn't appear to have any surprises.
I have all of the parts I need so those tasks can begin right away.

The keypad just needs some cleaning of the switching contacts.

The floating chassis needs new lockdown bushings.

The servo spindle pulley may need replacing with a new aluminum pulley.  I will further evaluate the condition of the plastic pulley.

I will also check the servo motor vibration damping material to see if it needs new material.

The ES and SO switches need replacing. I should be able to source those myself.

On to the circuit board work ...