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Beogram 4002: Restoration of DC Motor Video Published - Check It Out!

By popular request (really, I got quite a few emails about this!...;-), I finally completed my Beogram DC motor restoration video! It demon...

Saturday, June 24, 2017

Beogram 8000: Trouble-Shooting Test Phase 1

I made the choice to try switching the Beogram 8000 control panel board first in the trouble-shooting of the intermittent record play interruption. This is the problem where occasionally the Beogram tonearm lifts to the Pause position while playing a record.

This is the easiest thing to check first and I kind of suspect the photo resistor circuit in the control panel on this Beogram anyway. When I made the service manual adjustments earlier in this restoration I noticed the adjustment for the adjustment screws were quite a bit different between the forward (<<) and reverse (>>). The adjustment screws control how much light shines on the photo resistor. The service manual says the normal voltage across those resistors (when forward and reverse are not engaged) is 620mV.

The following picture shows the control panel board removed. The position of the adjustment screws are where they needed to be to get the 620mV measurement. The difference in position of the two screws make me think one of the photo resistors is weaker than the other. Perhaps that is the reason for the fault I am trying to fix.






















On the spare control panel board in the background you can see what I expect their positions to be like in relationship to each other.

One annoying thing about this adjustment is that B&O didn't provide good test points to check and adjust these controls without opening up the Beogram. It is easy to open just the control panel so if there were a nice test connector there I could check and make this adjustment after the Beogram is closed up.


The P5 connector pins 3, 4 and 6 are the nodes necessary to measure for this adjustment.
So I decided to add a test connector that I can access with just the control panel open. I also decided to do this test with one of my spare Beogram 8000 control panel boards.


























I used a female connector for the end so I could leave the test connector attached. The picture above shows the test connector with the male test plug attached.

The test connector works great!  The Beogram 8000 is all closed up except for the control panel and I can easily use the test connector to make the adjustments.





























I discovered that I will have to remove the test connector in this first attempt as the 24 gauge wires are too big and interfere with closing up the control panel all the way. If I want to have a "leave in" test connector I will have to go to a 30 gauge wire.

For now though it is time to return to the record play testing of this Beogram to see if the control panel was the problem. I am using the spare control panel board with the test connector and adjusted to the voltages specified by the service manual. On this spare board both adjustment screws are pretty symmetrical so that is a good sign that both photo-resistors are a pretty good match.

I am now on the last side of the second record play test. Only about eighteen more uninterrupted record plays (36 sides) to go for me to say the problem is fixed.


Friday, June 23, 2017

Beogram 8000: Dust Cover and Lid Repairs

Continuing the current Beogram 8000 restoration project...This turntable arrived with the metal deck lid already removed and the dust cover detached. The dust cover hinge assembly was all apart and the attachment hook piece that the lowering mechanism connects to was loose from the dust cover.


























I re-attached the hook assembly to the dust cover using epoxy (quick dry this time). Originally this piece was attached with double-sided tape. The hook assembly needs to be attached to the dust cover and not loose in order for the dust cover raising and lowering to work properly.


























Here are the leaf spring and sliding assembly that controls the raising and lowering of the dust cover.


















The 2mm allen wrench is used to adjust the tension of the leaf spring so the dust cover can be left in any open position or all the way closed.





















That is just right. I also installed new rubber bump pads where the dust cover contacts the deck.






















Just as I did with the old double-sided tape residue on the deck, I removed the residue from the metal lid hinge attachment plate. I aligned the metal lid where it needs to go and created a hinge at the front using some painter's tape. This allows me to tilt the lid towards the front when I apply new double-sided tape to the rear hinge plate.




























































I discovered the metal door had no damping.  When the lid is lowered you are supposed to be able to let go and the lid will gently lower by itself. This lid just dropped down without any damping. All of the damping grease was gone.  Fortunately I have some damping grease for this application.  I have to use it on the lids of the Beomaster 8000, Beomaster 6000 and the Beocord 8004/9000 units.


























I applied enough grease where the lid damping was in effect again. Now it works like new again.






















Here is the completed dust cover and metal lid repair.



The dust cover and deck lid were the final pieces of this Beogram 8000 restoration. Normally I would be packing this unit up to send back to its owner. Unfortunately I had a couple of intermittent instances during the record play testing. The fault I observed was the Beogram tonearm went into the Pause position while playing a record. However, I could not find anything wrong by inspection. The tracking weight was fine, the cartridge is good and I had played quite a few records without a problem.

I decided to change the phono cartridge anyway and started another round of record play testing. After fourteen record albums (all the way through, side 1 and side 2), the problem finally re-occurred. This is not the type of problem you want to encounter. Will I have to wait another fourteen record plays to try and catch the fault?

After consulting my usual repair sources for ideas I have decided to start with the easiest and work my way down to the more difficult (opening up the Beogram again). So tomorrow I will recheck the forward << and reverse >> voltages in the control keypad. I might also try swapping the keypad assembly with one of my spares.

Wednesday, June 21, 2017

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.

































Monday, June 19, 2017

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.


Friday, June 16, 2017

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.


Wednesday, June 14, 2017

Beogram 8000: Taking A Little Test Drive

Today is the day to try out this beautiful Beogram 8000 and see how it sounds.

I reconnected the floating chassis in the cabinet with the aid of a nice little hook tool I found a few years back. It is perfect for lifting the chassis support wires on and off the leaf springs.
























For the black metal deck lid in the tonearm compartment I had more old double-sided tape residue to remove. So more GooGone and scraping.






















For the re-attachment I used 3M automotive double-sided tape. It is easy to use and does a great job here.













































Next was a few iterations of putting the platter on and off as I adjusted the leaf springs to get the deck and platter surfaces aligned with each other.

















Now the Beogram is ready for a test drive.  Just need to swap out the MMC 4000 cartridge with a nice MMC 20CL.






















For some reason I was in the mood to hear the Rolling Stones It's Only Rock 'N Roll so hooked the Beogram up to my office system, sat back and relaxed.
























It's only B&O but I like it.