Beogram 4002 (5513): Another Beogram From Houston - Electrical Work

Continuing the Houston Beogram 4002 restoration with the electrical work, here is the reworked main PCB.

Before

After

Some details to point out are the replacement of the speed select relay and the trimmers for the platter speeds (33.33 and 45).

The old trimmers for the platter speed adjustment have trimmer adjustment slots on the top and bottom.
The Beogram 4002 main board mounts where its trace side faces up so the speed adjustment is made from the underside of the board.  That is why the new trimmers are mounted upside down...so their adjustment screw can be accessed from the trace side of the board.

Here is the trace side of the main board.  You can see the speed trimmer adjustment screws.

Next are the replacements of the Beogram 4002 main board Darlington transistors IC1 and IC4.
Other Beolover Blog posts show the replacement of these two transistors with new transistors as a precaution against the aging Darlington transistors the Beogram 4002 uses for its power supply (IC1 21V) and the solenoid actuation (IC4 30V).

Another possible transistor replacement is 1TR3.  It is in the arm detector circuit the Beogram 4002 uses to determine if a record is on the platter or not. On the Beolover Blog restorations of Beogram 4002 (and 4004) turntables we check the 1TR3 transistor Hfe value to make sure it is good (typically, above 500).  If it is not, we change the transistor.  

Regardless whether 1TR3 is replaced and whether the lamp in the Fixed Arm (Detector Arm) is replaced, we do change resistor 1R26 from a fixed value (1Mohm) to a trimmer (usually a 2Mohm or 5Mohm trimmer).

This photo shows a 5Mohm trimmer for 1R26 installed on the trace side of PCB1.

The new trimmer will remain there for a while until I finish the rest of the electrical restoration work and am ready to test the Beogram.

The Beogram output board is next.
Here is the before photo of the output board.

Here is the after photo.

The only changed components on the output board are the Beolover replacement muting relay, a new electrolytic capacitor for C1 and the addition of a toggle switch to select whether the Beogram chassis ground is connected to the signal ground.  We have found that different grounding conditions can exist with various preamplifiers that result in ground loops.  Those cause hum in the phono signal and is noticeable during record play.  The grounding switch provides another option to handle that scenario.

Next, I replaced the incandescent lamps for the platter speed indicator panel.

Here is a little bit closer look at the original lamps...

...and the Beolover replacement lamps.  

The incandescent lamp in the Fixed Arm for the Detector Arm circuit was also replaced with a Beolover replacement LED assembly.

I changed out the Beogram 4002 control button panel with a refinished one.  The old panel was in bad shape.

The button panel contacts were oxidized pretty good so I cleaned them up to a nice shiny finish again.

Here is the button panel and contacts reassembled.

As I started installing the floating chassis components back into the Beogram 4002 cabinet, I replaced the original reservoir capacitor with a new Beolover capacitor assembly.  This new Beolover replacement component is very easy to install.

I also replaced the original DC Platter Motor with one that Beolover had refurbished for me.

Now I could install the circuit boards back into the Beogram 4002 cabinet and make some electrical adjustments.

With the electronic components re-installed in the Beogram cabinet it was time to tackle the adjustment of the Detector Arm Circuit.  The new 1R26, 5Mohm trimmer needed adjustment so the DC voltage measured at the 1TR3 collector is 4 VDC.

With the steady state voltage adjusted on 1TR3 the new 1R26 trimmer can be moved to its final position on the component side of PCB1.

Another PCB1 adjustment is with trimmer 1R88.  This trimmer adjusts the voltage at the collector of 4IC1 which is the sensor for tangential arm position. That is the sensor that receives the infrared light from 4D1 as the position slide moves between light and sensor during arm movement.  The light, sensor and position slide detect the arm set down points for various size records as well as the run-out groove detection.

The 4IC1 collection should be set to 5 VDC when the clear portion of the position slide is between the sensor and lamp.

So far all of the adjustments and measurements have worked out as called for in the service manual.

I continued on with the calibration of the tone arm groove tracking.
For this adjustment I like to make a crude adjustment with the bracket connected to the base of the tonearm which holds the aperture slot controlling light to the tracking sensor.

Note that I also make this crude adjustment with the eccentric tracking adjustment screw in its center position.  That is so I have room to make the fine adjustment in either direction.

I adjust that bracket so the arm can be lowered and it just stays put (it doesn't try to move forward on its own).

After that is achieved I loosen the set screw for the eccentric (fine) adjustment screw.

A test record can now be placed on the platter (without a platter belt).
The tonearm is advanced to a center track on the test record and lowered.

The arm should not try to advance.

Manually rotating the platter with the test record should result in the Beogram servo motor turning to advance the arm within one revolution of the platter.  It should advance the arm every platter revolution after that.

The eccentric adjustment screw is used to dial in that calibration.  
Extra fine adjustment can be made with the small trimmer on top of the Beolover tracking sensor lamp assembly.  Those adjustments increase or decrease the intensity of the LED used as the sensor light source.

This photo shows an adjustment with the eccentric screw.

Using an oscilloscope I measured the empty platter signal at the 1TR3 collector to check the health of the sensor output.

Two last measurements before actual record play are to re-install the platter belt and adjust the 33.33 RPM and 45 RPM platter speeds.

For these adjustments I use the Beolover RPM Tool as the measurement instrument and the two speed trimmers on the main, PCB1 board.

The owner of this Beogram 4002 also would like the Beolover Remote Commander installed as part of the restoration.

My next steps will be to first, finish reassembling the Beogram 4002, then some quick test play of some vinyl records.  

After that I will install the Beolover Remote Commander and resume testing record play on this Beogram (the real fun part).

Beogram 4002 (5513): Another Beogram From Houston - Mechanical Work

The restoration work on this Beogram 4002 (Type 5513) begins with the various mechanical restoration tasks.

Those include cleaning out the debris from the cabinet base and some disassembly of the floating chassis components for cleaning and lubricating.

The arm lowering & raising lever is attached to the fixed arm.  The pivot for that lever can occasionally get gunked up so we typically remove it for a clean and lubrication.

The arm lowering damper is also cleaned.  The rubber washer on the end of the plunger gets replaced with a new washer and the metal part of the plunger is lightly lubricated with a silicone lubricant.

The tangential arm spindle parts are removed for cleaning and lubrication.
I don't immediately re-install the spindle however as I find it easier to make a few Service Manual mechanical adjustments with the tangential arm assembly free to slide back and forth.

Before making any Service Manual mechanical adjustments I like to move the four set screws that sit underneath the two metal rails the tangential arm assembly rides on.

These set screws are for adjusting the height of the rails but the slotted end to make the adjustment with sits underneath the floating chassis.  I remove them and re-insert them from the top.  This allows any change in their height to be made from the top side of the floating chassis without having to remove the floating chassis from the cabinet.

Here is a photo of one of the re-inserted set screws.

That gives a little peace of mind in case some change in the tangential arm assembly height is necessary.  Normally it shouldn't be but the set screws allow about 3 mm of height adjustment.

Next I reassembly the tangential arm assembly and go through the adjustments to make sure the arms are perpendicular to the back rail, parallel to each other and have the proper distance to the platter.

The Service Manual says the distance between the Fixed arm and Tonearm is 7.7 mm.

The top of the Fixed arm to the top of the platter (metal) surface has to be 23 mm.

After that is set the tops of the two arms (Fixed and Tonearm) should be even.  If they are not, the Tonearm height can be adjusted. 

With a phono cartridge mounted I check that the Tonearm and cartridge vertical alignment (azimuth) is good.

I set the Tonearm lowering limit so the stylus of the cartridge is about 0.5 mm above the lower platter rib.

I calibrated the tracking force of the Tonearm/Cartridge so that it measures 1.0 gram with the tracking force knob set at 1 gram. 

After that calibration I set the tracking force knob to 1.2 grams.

Before installing the Beolover Tracking Sensor Lamp component to the Beogram 4002 Tracking Sensor Assembly, I checked and adjusted the metal aperture so it is 1 mm above the Tracking Sensor.

The Beolover Tracking Sensor Lamp was then installed followed by the Tangential Arm Assembly spindle parts.  The plastic pulley on the spindle was replaced with an aluminum pulley.

When the spindle was installed I lubricated it with a mixture of grease and oil.  Not too thick and not too thin.

The floating chassis components can now be re-installed in the Beogram 4002 cabinet base where the suspension will be adjusted so the top of the platter is even with the cabinet aluminum deck.

Along with that, the platter motor and reservoir capacitor assemblies will be installed.

I'm pleased with the mechanical adjustments so far.  The re-installed floating chassis aligns good with the aluminum deck plate so it is on to the rest of the electronic restoration tasks.

Those include the restoration work on the main PCB, the output (audio muting) PCB, the LED lamps for the speed indicators, the arm detector lamp (in the Fixed arm) and the contact cleaning on the Beogram control panel buttons...Plus all of the related adjustments.

Beogram 4002 (5513): Another Beogram from Houston

The Beogram 4002 Type 5513 is turning out to be a popular Beogram in Houston.
Here is the initial assessment of another one in need of restoration.

The dust cover is functional and can be kept for now as the supply of newly manufactured Beogram 400x dust covers have become scarce for the moment.

Cosmetically this Beogram clearly has a problem with the condition of the keypad buttons.

On the bright side...the wood trim on this unit is in great condition.
The deck panels, platter and tangential arm assembly also look good.

This keypad though, will need replacing.

The rim of the sub-platter has some sort of residue on it.  I will try to clean that off.

Inside the Beogram 4002 cabinet is pretty typical.
There is debris from the disintegrated transport lock bushings everywhere.

The photo shows the DC platter motor already removed.  I already extracted the platter motor and sent it to Beolover for restoration.

Here is a picture of the Beogram 4002 cabinet with most of the components removed.
I will vacuum the cabinet base out to get rid of all of the loose debris.

Here are the removed components.

The floating turntable chassis, boards, control panel and display panel.

The two boards (main board and output audio signal board) look normal...and ready for restoration.

I opened up the servo motor case to check what the damping material looked like.  Often the foam padding is deteriorated and crumbling into little pieces.
This one is still intact and fine.

I removed the arm lowering damper for cleaning.  It also looks it good shape.

Here is the tangential arm tracking detection sensor opened up.  It will be replaced with a Beolover replacement part.

The SO (stop) and ES (end stop) switches look to be in good physical condition.  They will be functionally tested later along with the arm position sensor and infrared lamp.

The tangential arm assembly itself appears to be in good condition too.

While I have everything apart I will clean and lubricate where necessary and perform some early service manual adjustments.

Other restoration tasks will be electronic restoration work on the two circuit boards, switch contact cleaning.