Lubricating Sintered Bearings in Beocord 8000/9000

GL

Glitch

Bronze

395 posts

Posted March 16, 2023 at 04:51 GMT ? Edited March 16, 2023 at 04:51 GMT

I'm looking for advice/discussion about lubricating the sintered bearings in a Beocord. I know that these were designed to be "lubricated for life", but I assume that the design life for these bearings passed many years ago. The picture above is the bottom capstan bearing. This looks pretty good (to me) with very little wear. The next picture is the wear surface of the upper capstan bearing. This has worn past the "porous" surface. What is the best course of action:

Re-lubricate the bearing using the clean and vacuum infuse methods. This seems like the right thing to do for the lower bearing, but I'm not sure about the upper bearing.
Run the bearings "wet" and continually monitor/maintain to ensure that the bearing doesn't run dry. (i.e. the pores are closed so the bearing can't work as originally designed)
Both 1 & 2
A combination of 1-3 and swap the upper and lower bearings.
Replace the bearings with news ones. Are the parts available?
Something else?

The bearings on the capstan shaft and idler shaft should be pretty easy to work with. The motor bearings are a different story. I tried searching the archives for past discussions but mostly found that people just replaced the parts with new or "better condition" used parts. Glitch

SO

sonavor

Bronze

265 posts

Posted March 17, 2023 at 22:38 GMT ? Edited March 17, 2023 at 22:38 GMT

#699846

Hi, The sintered oil bearings on the BG8000 - BG9000 DC motors are much like the Beogram 4002/4004 DC platter motors and do require restoring. There is a big difference in the disassembly and reassembly however. Not to mention the testing. The Beocord motors are housed inside a metal housing that also includes a small, round circuit board. The trimmer resistor for adjusting the Beocord motor speed is on that board. If the trimmer resistor needs replacing I haven't found a suitable replacement yet as it has to be a really low profile device. Removing the metal, outer shell can also be a chore as it is fit together with rivets. So those must be carefully cut out. I reassemble them by tapping holes and using screws to fit the housing back on. The Beogram 4002/4004 DC motors are pretty easy to test after restoring the motor bearings and reinstalling the platter motor. You can run the platter motor for however long you want to test it with and use something like the Beolover RPM sensor connected to a computer. The Beolover RPM sensor device will update the speed measurement every 10 seconds. With the Beocord 8000-9000 motors you would have to rig up some testing device to perform a similar level of testing on the restored motor. Of course you can do a short test with a 3KHz test cassette and measure the tape play with a WOW/Flutter/Speed tester to verify you get an accurate 3KHz output but the test cassettes are usually only a few minutes long. That is better than nothing but I would prefer a longer motor test in the case of a rebuilt motor. -sonavor

SO

sonavor

Bronze

265 posts

Posted March 18, 2023 at 04:20 GMT

#699848

I re-read your original post. I was thinking motor bearings as I read it but I see that you are talking about the bearings on the capstan bearing. I haven't done anything with those parts other than treating them with some synthetic oil. However, I think it would probably be better to re-infuse those bearings...and probably the two sintered bearings in the clutch assembly. If you decide to go that route I would be interested in hearing your results. -sonavor

GL

Glitch

Bronze

395 posts

Posted March 18, 2023 at 17:00 GMT ? Edited March 18, 2023 at 19:04 GMT

#699854

SO

sonavor

Bronze

265 posts

Posted March 18, 2023 at 20:44 GMT

#699861

Option 2, running the motor by continually trying to keep it wet doesn't sound like a good idea to me. I have come across a couple of Beocord 8000-9000 motors that were squeaking pretty bad. The bearings were the source of the problem. As I said, I believe the motors are quite similar to a Beogram 4002/4004 DC platter motor which we know need refreshed bearings after forty years. I use a Dremel tool with a small cutting wheel to remove the rivets of the outer case/shell. Once you get to the motor, the disassembly and restoration of the bearings should be the same as on the Beogram 4002/4004 DC platter motor. -sonavor

GL

Glitch

Bronze

395 posts

Posted March 19, 2023 at 18:25 GMT

#699877

chartz

Bronze

240 posts

Posted March 19, 2023 at 19:01 GMT ? Edited March 19, 2023 at 19:53 GMT

#699878

Unfortunately the Beocord 9000 motor is specific to these decks. It is irreplaceable. So unless you know what you’re doing, send it to someone who can do it in their sleep like Rudy! I did mine ten years ago and it just needed a new set of belts and a drop of oil here and there, always a good idea while it’s in bits and pieces.

Jacques

SO

sonavor

Bronze

265 posts

Posted March 20, 2023 at 05:26 GMT

#699894

As I understand it, the motor assemblies for the different Beocord models (BC8000, BC8002, BC8004, BC6000 & BC6002) have a different motor assembly than the BC9000. BC9000: 12M1 8400112 Motor -- Pulley 12101 2722027 BC8000 through BC8004 (including BC6000, BC6002): 12M1 8400101 Motor -- Pulley 12101 2722027 However, I believe that the actual DC motor for the Beocord 8000-9000 (the DC motor inside the assembly) is the same. It is very similar to the Beogram 4002/4004 DC platter motor and I had Rudy re-infuse the oil in the bearings of a Beocord 9000 motor. Martin Olsen would know for sure so maybe he will add something to this thread. The Beocord DC motor is not easy to get to as it is inside a metal, outer shell that must be cut open. I have attached some photos of the Beocord 9000 DC motor disassembled. Compare the actual motor that is shown in the disassembled photo to this Beogram 4002 DC platter motor that Rudy restored for me. You can see how much alike they are. The biggest difference is the motor assembly. The Beocord 8000-9000 motor assemblies contain the DC motor, the metal shell and a circular circuit board. The circuit board has a small trimmer resistor for adjusting the motor speed. In my case, this Beocord 9000 motor had a failed speed adjustment trimmer. The motor was also noisy before the bearings were re-infused with oil. I had to cut open the metal outer shell to open the motor assembly and in order to reassemble it later I drilled two small holes and tapped them for two M2 screws. It makes sense that these Beocord motors will eventually start making some noise just like Beogram 4002/4004 platter motors do with age...until someone re-infuses the bearings with oil. -sonavor

chartz

Bronze

240 posts

Posted March 20, 2023 at 20:31 GMT ? Edited March 20, 2023 at 20:34 GMT

#699908

Thanks for the pictures John. Very useful. The trimmer is very thin. Have you found a replacement? The motor does look similar to the Beocord 6000/8000 one but is it the same? How are the two speeds obtained? Jacques

Jacques

SO

sonavor

Bronze

265 posts

Posted March 20, 2023 at 23:17 GMT

#699918

Hi Jacques, I found some more pictures where I took a Beocord 8002 motor assembly apart and photographed it next to the Beocord 9000. I attached the photos in this post. I also included a photo of the assembly back together. In the photo with the two different motor assemblies, the BC8002 is on the left and the BC9000 on the right. Regarding the trimmer resistor, I need to check on what its value is again. I may have to open the ones I reassembled and measure them. The motor PCB and components is not in the Beocord service manual. I was thinking of adapting a surface mount trimmer as a replacement but while that would probably work, it could be a pain to implement it. Especially because it is meant to be adjusted from outside the metal case, through the access hole. Then I realized that the adjustment hole for the trimmer and the PCB is right against the bottom of the metal cover. I think it would be easier to run three leads out the back of the round PCB, where the trimmer mounts, and attach a nice Bourns trimmer outside the case. It would be much easier to adjust and there is room where it won't interfere with the cabinet. The length of the wires would only be 10 to 12 mm as the PCB is right on the other side of the case. That is as far I got with it as I got busy with some Beogram and Beomaster restoration projects. These Beocord motors were a little side project to investigate the possibility of restoring them. The restored motor did run good but I discovered that I still need to mess with some of the PCB components to dial in the speed as I couldn't dial in the speed I needed with just the trimmer. However, I did prove to myself that the motor bearings could be re-infused by Rudy successfully and that reassembly and use in a Beocord would be possible. There are just a few things I need to go back and tweak. Maybe sometime this year :-) Right now my restoration backlog is just to big to even consider any Beocord projects. -John

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