Beogram 4002 Type 5513: Changing out the tonearm phono cartridge connector

This Beogram 4002 project has been on hold since the end of June in order to get a fresh shipment of Beolover replacement parts for the Beogram 400x tonearm cartridge mounts. Now that they are available I snagged one to install in this Beogram.

This Beogram 4002 unit has a defect in one of the cartridge connector contacts. I don't know if the defect came that way from the factory or deteriorated with use. The owner has had some problems with cartridge mounting so we felt it warrants changing out the connector on this one.

It is unusual to replace the cartridge mount in the Beogram 4002. It is the Beogram 4000 that quite often has broken (or near broken) cartridge mounts that require a replacement. In any case we hate to steal a working cartridge mount from another Beogram because that still means a Beogram is left without a working tonearm. So having a replacement part such as the Beolover connector is a wonderful solution.

I begin the procedure on the right side of the Beogram so I can loosen the two mounting screws for the tonearm.

There is a small board in the tonearm that transfers the phono signal from the very thin wire in the tonearm base to the color coded wire that travels down to the cartridge connector. This allows the tonearm to be de-soldered and removed at small board and we can use the color coding to put things back correctly.

I un-solder the red and white wires from the top of the board with the tonearm in its normal position.
Then I flip the tangential arm assembly over to get to the underside of the board for the blue, green and gray wires. The tangential arm assembly rails and drive screw have to be removed to allow this maneuver. It is worth it though as you don't want to make a mistake here.

With the tonearm completely removed I dip the end with the connector into some boiling water for a minute then into ice water. A push on the connector through the back end of the tonearm should break the connector loose so it can be removed.

This one came out on the first attempt. Sometimes it takes more.

If you have to re-use the tonearm wires then take care in this operation. I always like to install new wires that are a little smaller (36 gauge).

Here is the original cartridge connector removed and opened up. It comes in two halves (an upper and lower). This repair keeps the lower half and replaces the upper part of the connector.
As you can see in the pictures, the red highlighted areas show this connector has a broken or worn area of one of the contacts (left channel low signal).

Here is the Beolover replacement part for the upper section of the connector. I tinned the four contacts in preparation for the new phono wires.

I replaced all five original wires in the tonearm with the same color 36 gauge wire except for the ground wire which I changed from gray to black (just a personal preference).

To keep the wires down in the channel before gluing the connector halves together I use some Aleene's Tacky Glue. It is a handy glue that is removable if necessary. I don't want permanent epoxy here.

Once the glue is dry I put the wires right at the connector end into a small bundle so it will be easier to remove this connector again in the future. When I glue the two connector halves back together I use Aleene's glue again for that and I attach a cartridge so I make sure I have the connector pieces aligned properly.

When I re-insert the connector and wires back into the tonearm tube I place a little more Aleene's glue on the sides of the tube (on the inside). That way no glue will get on the end of the connector or the cartridge.

The above photo shows the cartridge removed but when I inserted the connector for real I always have a cartridge attached to insure a proper installation of the connector.

The cutting, stripping, tinning and soldering of wires onto the transfer board takes some patience. I did the red and white wires on the top first again, then flipped the transport over for the remaining three.

The transport is then flipped back over to its proper position and the tonearm is carefully re-attached.
You have to be very gentle tucking the phono wires back into the tube as you re-install the tonearm to the tonearm mounting hardware.

After the tangential arm assembly is put back together I did have to recheck the following alignment adjustments: the stylus tracking path, the tracking force weight and the tangential arm tracking sensor operation.

Back to an audio system for record play testing... both channels play beautifully through the new cartridge connector.

Beogram 4002 Type 5513: Fit and Finish Rework

These Beogram 4002 restoration projects are rewarding and fun but they often require going back over things multiple times. I had this Beogram playing really well and once the trim and deck pieces were fitted, this deck would be done. The problem was I wasn't happy with the resulting fit of some of the pieces.

The tonearm cover didn't fit quite right. you can see in this picture that the tonearm cover is on all the way but sits slightly crooked. If you look at the tonearm cover between the fixed arm and tonearm carefully you can see that the center divider is not evenly spaced.

This picture shows the tonearm cover problem from head-on view. You can also see that the deck trim doesn't line up well. There is too big of a gap between the two deck panels for my liking.

Another problem cropped up during this final fit check. The record tracking started to hang up and not track. I had to remove all of the deck trim to investigate. At first I thought it was related to the tonearm cover but the problem remained even with the cover removed.

I exercised the tonearm travel a bunch of times to see if I could spot a problem. To my surprise I could visually see the tangential drive motor and screw slow down during fast forward travel near the center of the platter. This was puzzling so I immediately rechecked the drive screw lubrication and the belt. I finally discovered the problem was with the new drive pulley.

Since starting this project our drive pulley supplier, Nick (in the UK), sent me a new re-designed aluminum pulley for the Beogram 4002 turntables. Here are some pictures of the pulleys for the Beogram 4002.

The new, version 2 pulley is much closer to the original pulley. It has the four holes around the center hole like the original, plastic pulley. Those are for certain Beogram 4002 versions that had an optical sensor attached. The new pulley is lighter weight than the version 1 pulley.

As soon as I swapped out the drive pulley to use the version 2 model the tracking problems went away. Looks like I will be ordering a few of these new pulleys going forward.

To address the arm cover fit I ended up going through all of the fixed arm and tonearm alignment procedures again. This time I added the fit of the tonearm cover to the adjustment checks (before locking down the arm positions).

To fix the deck panel gap problem I had to go through all of the guide washer adjustments again as well as check the posts on the leaf springs. It took a good number of iterations to get the fit right.

Here are the final results of the rework. The deck lid seam looks good, tonearm cover is straight and the Beogram is back to full functional play testing again.

Beogram 4002 Type 5513: Some Cabinet Work

This weekend I worked on getting the Beogram 4002 re-assembled with its cabinet trim and deck cover. I removed the rosewood trim so it would be out of the way and not be susceptible to accidental damage during the other restoration steps.

The rosewood trim attaches to a metal frame that slides out to unlock and slides in to lock the Beogram 4002 cabinet. The metal frame has five guide washers that are almost always broken on the Beogram 4002 units. This one was no exception. The guide washers are a special designed part as shown in this earlier Beolover post.

Here is this Beogram fitted with the Beolover 3D printed guide washer replacements.

At first you might think these can just be refitted with some flat washers from the hardware store. Why buy the special printed parts. I can tell you these guide washers make a big difference in properly assembling the Beogram cabinet. As you can see in the Beolover blog post, the guide washers mount in place to provide a proper guide for the cabinet locking frame to slide along.

As I was attaching the cabinet trim/lock I noticed the frame was separating from the rosewood along the front.

This had to be epoxied before I could continue. It is not a good idea to glue it in place. Glue can be messy and before you know it you have a crisis on your hands. Be safe and properly remove the trim piece to work on it independently.  I cover all of the rosewood with good painter's tape so I don't have to worry about scratches or glue residue on the finish.  This picture shows the glue areas ready to receive the epoxy.

You can't have too many clamps. A couple of years ago I found these little miniature clamps like the big ones I have in my workshop. They are great for small things like this.

For this type of gluing I like to use a slow drying epoxy so I don't have to panic in getting excess glue wiped off and making sure the clamps have everything aligned.  I let this dry overnight.

The next morning the trim/locking piece was ready to use. Now I could finish attaching it to the cabinet with the five guide washers.  It fits good and looks good.

Beogram 4002 Type 5513: First Listening Test

Today I finalized the Beogram mechanical adjustments. With my digital scale powered up again I locked down the calibration of the tonearm tracking force counter-weight. Like Beolover has done I removed the M3 counter-weight adjustment screw from the back of the tonearm and fitted it with a tightening nut as the means to lock in the calibrated position. Doing that helps to insure the calibrated setting doesn't get moved during any shipping or handling of the Beogram.

Once the counter-weight is in the desired position I tightened up the locking nut and applied a dab of glue as one more bit of insurance. The Aleene's Tacky Glue can be peeled off in the future if another adjustment is ever needed.

I also applied a dab of the glue on the adjustment screw for the tonearm lowering limit.

This picture shows the Beogram tracking force calibrated to 1 gram with the adjustment knob set to 1. Because most of the MMC cartridges are at least 1 gram recommended tracking force I calibrate the adjustment knob to the 1 gram position instead of zero.

I checked the Beogram record tracking one more time and everything looks ready on this Beogram for a record play test.

I changed out the MMC 4000 cartridge I used for the service manual adjustments with an MMC 20CL cartridge for the play test.

Two sides of Golden Earring (sorry, 70's was my era) played perfectly. I will now spoil myself the rest of the weekend alternating play between this Beogram 4002 and the Beogram 8000 that are now in the play test stage.

Beogram 4002 Type 5513: Service Manual Adjustments

The rebuilt platter motor from Beolover arrived so I will be testing it out soon. In the meantime I have the service manual adjustments mostly complete on this Beogram.

The longest part for me on these turntables is the platter height and leveling adjustments. This Beogram was out of level and the height of the platter to the top of the fixed arm was less than the required 23mm distance.

To make the adjustments the platters are removed and the center, threaded bearing is adjusted up or down as necessary. There is a large nut designated "A" in the service manual. It is loosened in order to move the bearing. There are three other bolts around the bearing that are used to level the platter.

I use a number of measurement tools to check the platter position. Including some small levels. Getting everything right takes me quite a few iterations of small adjustments.

I also check if the fixed arm is level.

When I had the floating chassis removed from the cabinet I like to remove the small set screws for the tangential carriage rails and flip them around so they screw in from the top. I guess they are installed from the bottom to discourage owners from adjusting them. However, when it is necessary to adjust them it is much easier to do when you can just lift off the end of a rail and make an adjustment. Otherwise you have to remove everything from the chassis again.

Normally I use a small, digital scale to check the cartridge tracking weight but due to some untimely dead batteries I reverted to the Beogram's manual check.

That will do for now.  I will recheck it when I get the digital scale powered up again and calibrate the tonearm counter-balance.

To check the travel path of the cartridge on the tonearm I use a string from the platter center to the edge of the cabinet.

I adjusted the tonearm lowering limit where it is just above the first rib. This will prevent accidental damage to the stylus and cantilever if the platter detection ever fails.

Last is the record tracking adjustment. All of the tests so far were made with the platter belt removed so the platter won't turn. On this record tracking test the platter will be manually turned by hand while observing the tangential arm motor turning to keep the tonearm tangent stylus travel path. Any adjustments necessary are performed with an eccentric screw at the base of the tonearm.

The tonearm checks are done. I will revisit the tracking force and calibrate the counter-weight later. This turntable is almost ready to try out with a preamp.

Beogram 4002 Type 5513: Finishing Up The Tangential Arm Position Sensor & The Fixed Arm Platter Sensor

It was great to see Beolover has the platter motor restored for this Beogram 4002 project. While it is being packed up for shipment back to me, I adjusted the voltages for two of the new sensor lamps in the Beogram.

The new LED replacement light source for the tangential arm position sensor was a little weak for me to leave it installed. It appears to work fine but with the 1R88, 25K ohms trimmer set for the highest LED output, the maximum voltage I could get on the 1TR17 base was 0.695 VDC. I would prefer for the 4D1 light source to have enough juice to max out the sensor then use 1R88 to dim the LED down where the base voltage of 1TR17 is 0.7 VDC.

That meant ordering a brighter LED. Here is the circuit as shown in the service manual. The 1R88 trimmer controls the current to the lamp source, 4D1.  That increases or reduces the LED light output to the sensor, 4IC1. The sensor controls the base of 1TR17.

With a new amber LED installed (Cree C503B-AAN-CY0B0251) for 4D1, there is plenty of light on the sensor now.

In operation the black bars on the tangential arm transport scale affect the light source on the sensor causing a change in voltage at 1TR17.  The output of 1TR17 drives analog control logic for the operation of the Beogram. It is quite interesting how the control system works on these analog 400x turntables compared to the 800x series which use a microcomputer for their control.

Here is a picture of the tangential arm position scale.

Here everything is put together.

The new LED does max out the sensor where I get a voltage of around 0.75 VDC at the base of 1TR17.  Using the 1R88 trimmer to adjust 1TR18 so the LED has less current, I got the desired 0.7 V at 1TR17's base.

Next up is the voltage adjustment on 1TR3 for the fixed arm sensor - the detector arm circuit. Two reference posts by Beolover show the relevant circuit and the installation of a 2M ohm trimmer in place of the 1R26, 1M ohm resistor (between the base and collector of 1TR3).

Here is the 1R26 resistor on the main board before switching it out with the 2M ohm trimmer.

Following Beolover's same procedure I temporarily installed the 2M ohm trimmer on the trace side of the board to make it an easier task of adjusting the trimmer setting while operating the Beogram.

Measuring the collector of 1TR3 to ground I adjusted the trimmer until I got to 4 VDC.

After the adjustment I de-soldered the trimmer and re-installed it on the component side of the board so it will be out of the path of the platter.

As a final confidence check of the detector arm circuit I connected a probe wire to the 1TR3 collector so I can view the resulting signal when the detector arm is over the platter.

I get a healthy 5.66 Vp-p minimum voltage when the arm is stationary over the platter and 6.16 Vp-p when the arm is moving across the empty platter.

These two sensor circuits are ready to go. The next tasks will be to run through some of the arm and platter mechanical service manual checks. After those I will adjust the tangential arm tracking of a vinyl record.