Beogram 4002 (5513): Adjusting the Sub-Chassis and the Platter, and RPM Calibration

Today I it was time to give the Beogram 4002 (5513) that I am currently reviving a properly adjusted platter and sub chassis. The goal is to adjust everything that the aluminum surface of the platter is flush with the aluminum panels surrounding it, while having the sub chassis centered between the upper and lower limits of the transport locks and the arms being also parallel to the aluminum surfaces. This is usually a pretty delicate process since so many things need to align. I have now a bit of experience with this and so after a while this Beogram looked very nice and up to spec. I recently made a couple videos that demonstrate this process:

Once the platter was adjusted I did a baseline RPM adjustment for 33.33 and 45 RPM using my recently developed BeoloverRPM device. Here is a picture of it in action:

This shows the readout after I already had adjusted 33.33 and then did 45:

Stabilizing
Measurement	starts
time:	0:0:9	RPM:	33.381
time:	0:0:20	RPM:	33.3782
time:	0:0:31	RPM:	33.3904
time:	0:0:42	RPM:	33.3987
time:	0:0:53	RPM:	33.4052
time:	0:1:4	RPM:	33.3937
time:	0:1:15	RPM:	33.4039
time:	0:1:26	RPM:	33.3882
time:	0:1:37	RPM:	33.3958
time:	0:1:48	RPM:	33.3817
time:	0:1:59	RPM:	33.3982
time:	0:2:10	RPM:	33.4025
time:	0:2:21	RPM:	33.4117
time:	0:2:32	RPM:	33.4088
time:	0:2:43	RPM:	33.3933
time:	0:2:54	RPM:	33.3916
time:	0:3:5	RPM:	33.3879
time:	0:3:16	RPM:	33.3815
time:	0:3:27	RPM:	33.4003
time:	0:3:38	RPM:	33.4095
time:	0:3:49	RPM:	33.4057
time:	0:3:54	RPM:	35.24
time:	0:3:55	RPM:	38.32
time:	0:3:56	RPM:	40.9
time:	0:4:0	RPM:	44.4733
time:	0:4:11	RPM:	44.8362
time:	0:4:22	RPM:	44.8325
time:	0:4:33	RPM:	44.8564
time:	0:4:44	RPM:	44.8543
time:	0:4:55	RPM:	45.0447
time:	0:5:6	RPM:	45.1634
time:	0:5:17	RPM:	45.1921
time:	0:5:28	RPM:	45.1968
time:	0:5:39	RPM:	44.8451
time:	0:5:50	RPM:	44.8174
time:	0:6:1	RPM:	45.2279
time:	0:6:12	RPM:	45.2203
time:	0:6:23	RPM:	44.7694
time:	0:6:34	RPM:	45.1452
time:	0:6:45	RPM:	45.2124
time:	0:6:56	RPM:	45.1949
time:	0:7:7	RPM:	45.1759
time:	0:7:18	RPM:	45.1953
time:	0:7:29	RPM:	45.2055
time:	0:7:40	RPM:	45.1998

It turns out that it is pretty difficult to adjust the RPM precisely with the standard single turn RPM trimmers that are in the Beogram originally. You can see at the and how I tried to get close to 45, but I always missed it by 0.2 or more by just very slightly moving the trimmer. This demonstrates that it is a great idea to put in multi-turn trimmers to get this right. On the other hand, I think it is difficult to hear such small difference...so this deck sounds now pretty good, especially with the lovely MMC20CL cartridge that came with it. I am listening to 'Song for My Father' by Horace Silver on Blue Note on it right now while writing this post! Wonderful!

I will give this Beogram some more listening to make sure there are no intermittent issues, but I think it is ready for duty again. This is Beolove!

Beogram 4002 (5513): Repair of a Broken SO ('Shut Off') Switch

This is a follow up to my last post about a SO ("Shut Off") switch that had lost its plastic actuator and hence caused trouble during shutdown of the deck. I set out to develop a 3D printed part to replace the missing plastic part. This shows the SO (left) and the ES ("End Switch", right) in comparison. The ES still has its plastic appendage, while the SO is missing it.

I took measurements and then went through a few 3D printing iterations to get a part that would come out right. Due to the small size this was pushing the limits of the 3D printer, so the outcome was significantly difficult from the 3D CAD design, and experimentation finally yielded a useful shape:

I glued it on with epoxy:

And now this Beogram can shut down again in an orderly manner:

On to the sub-chassis and platter adjustment.

Beogram 4002 (5513): Rebuilding the Arm Lowering Mechanism, Mechanical Adjustments and a Broken SO Switch

Today I rebuilt the arm lowering mechanism of the Beogram 4002 (5513) that recently arrived on my bench. It turned out that all linkages were stuck and that the damper was completely dry. The first step was to re-lubricate the damper to arm linkage and adjust the lateral arm parallelism. I took out the sensor arm fixture to get to the pin around which the linkage rotates:

Then I took the mechanism apart and cleaned everything of the hardened lubricants and re-lubricated with a small amount of silicone grease:

Then I put everything back together and made sure the arms are parallel. Then it was time to extract the damper and the solenoid linkages:

Here is a picture of the damper taken apart:

I lubricated it with a bit of synthetic motor oil and cleaned the old lubricants fro the linkage pivot points and re-lubricated those with silicone grease. Then I put everything back together and gave it a spin. While the arm was now lowering properly, the tracking mechanism was completely out of adjustment due to the arm alignment. So I had to adjust the tracking feedback. Hence it was time to crank out my least favorite record and stick on my dented MMC20EN cartridge to adjust the mechanism:

I made a detailed video about this process, which explains how to do it properly.

Then it was time to adjust the arm lowering limits to help prevent a cantilever extraction in case the sensor in the sensor arm dies. There is another video that shows how to do this. This was the result of my efforts:

The stylus is supposed to just clear the lower parts of the platter ribs when all the way lowered. The final task was to adjust the tracking force. Yet another video shows how to do that.

Then I played a record, which went well, but I had to realize that the 'Switch Off' (SO) switch that turns the deck off when the carriage is in its home position is broken. It is interesting to note how this manifested itself: When the arm returned to its home position on the right, the deck shut down, but the solenoid briefly came on and jerked with a loud 'clonk'. The reason for this is a missing plastic part that is needed to fully engage the switch, i.e. make the ground connection at the right point during the home movement of the carriage. Here is a picture of a good SO switch in a different Beogram 4002:

And here the broken one:

Note the missing small black plastic part right above the carriage pulley. If it is not there the switch terminals are not moved far enough by the aluminum tab on the position ruler preventing it from switching over to the GND pole. However, without the plastic part the switch the switch also forms a ground connection via the aluminum tab on the position indicator slide that is activating it when the carriage has arrived in the home position. This turns the deck off like a working SO switch, but a bit too early and perhaps with a bounce since the spring force between the tab and the switch terminal is weak. Hence the solenoid jerk.

Beogram 4002 (5513): A New Arrival - A First Look!

Another Beogram 4002 (5513) arrived recently. After an unplanned (yet interesting) delay with the Beogram 4000 that I recently rebuilt, it was time to have a look. I extracted it from the double box where an excellent packing job had prevented any shipping damage. A detailed video about how to do pack a Beogram properly is shown here.

Once I had it out, I took the hood off and had a look at the panels:

They are in very nice condition. The keypad shows the usual triple digit usage pattern indicating not too heavy use:

The STOP key is a bit pulled up, but not too bad. Then I had a look under the hood:

Everything looks quite nice...no obvious signs of 'human intervention' (usually the most challenging  and interesting repairs result from that...;-) and pretty clean. Also the transport lock bushings are still good, so there was no need to put the vacuum cleaner to it. Then it was time to plug it in. I pressed START, and nothing! After checking the fuses, which have corroded holders,

I measured the voltage at the reservoir capacitor, which yielded a healthy >30V reading. After establishing the presence of power, I then determined that P5 had come loose during transport. I plugged it back in and tried again. Now the carriage started limping hesitantly (due to a loose servo belt and hardened lubricants) towards the center of the record. Once it made it to the 30 cm set-down point it properly activated the solenoid, but nothing further happened. Moving the linkages by hand immediately suggested that the lubricants are hardened and that the mechanism needs cleaning and re-lubrication. A first sign of this was the non-parallel tonearm when I had a first look under the hood:

This is usually a sure sign that the arm linkage is stuck. So far so good. It seems mechanically all it needs is a good cleaning and some lubrication to get going again. After this I assembled the panels and put the platter on with the belt to check the platter and arm alignments. As usual the platter sits too low and the arms are not horizontal...this needs to be adjusted.

Other than that the cosmetic condition of this deck is really nice. The hood could use a deep polishing since it has a few deep gashes that can be felt with a fingernail:

One really wonders why people do not put a plastic bag and some foam pad on their Beogram hoods before they store them in their basements. But such is the world. Luckily, there are good polishing materials available these days.

Lastly, I had a look at the MMC20CL cartridge that came with the deck:

The sapphire cantilever and the tip looked pristine and everything appears well-aligned. So I stuck it on the Beogram 4000 that I am re-testing again before shipping, and put Eberhart Weber's "Fluid Rustle" on a pristine ECM pressing that I recently obtained from ebay and cranked up the volume on my Beomaster 6000 4-Channel. Absolutely gorgeous! This cartridge seems to be in pretty good condition!

So, the bottom line is that this is a very good starting point for a happy Beogram 4002 restoration! The deck is in a great cosmetic condition, which is usually the most important concern when it comes to investing money into a restoration.