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Beogram 400x projects

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sonavor
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Testing it with the platter so I could tell that the strobe is really working...
I had to move the strobe assembly back some to line up with the 60 Hz markings on the underside of the platter. This forced me to remove the strobe circuit mounting bolt so I will have to secure that a different way now. That shouldn't be too bad.

In this picture you can see the platter 33 RPM markings. The strobe circuit does indeed work.

This Beogram has come a long way. Initially it had problems because of a bad transformer, then it had a broken cartridge mount and the replacement transformer meant losing the original strobe lamp power source. The only things remaining to complete the full restoration is to re-install the mounting brackets for the chassis capacitors, secure the new strobe circuit board and restore the dust cover.


sonavor
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Here is the inside pretty well bolted down. You can see where the strobe PCB had to be moved slightly to position the lamps for the 60 Hz strobe markings. The wiring to the board makes for the board staying pretty well in place but I have installed a 3mm screw and washer to help hold it down. Eventually I want to cut a small strip of metal that will span the two available screw holes and clamp down that edge of the board. But this will work fine for me now. Now it is time to clean up my work shop and prepare for the next project. I also intend to spend the next, nice weather weekend polishing up my two Beogram 4000 dust covers.


Søren Mexico
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As always interesting how you find solutions where someone without your persistence would leave it in the corner.

As for polishing your covers, my experience is only hard hand work does it, I have tried with polishing pads attached to fast drilling machines, slow running drilling machines, with foam pads, with rubber pads, with lamb wool pads and whatever pads I could find, the only thing they did was a lot of mess all around the working space.

The best way is to find a table and good supports for the covers, aca a steady  cardboard box that fits inside the cover, cover the box with a cotton rag not to damage the inside of the cover, and then find a chair that fits a comfortable working height.

To decide how damaged the cover is, run a finger nail over the scratches if you feel them you will have to start with 60 or even 80 micron finishing paper, if you cant feel them it may be enough to start with 30 micron, if only swirl from dusting is visible you can start with 15 micron.

If only smaller deep scratches are there, I start with 60 micron only over the scratches and sand in one direction  until the scratches are no more visible I then go to the 30 micron and sand in direction 90° to the 60 micron grain all over the cover, until the 60 micron grain and other smaller marks are no more visible, the down to 15 micron and again 90° direction to the 30 micron until grain is invisible, then the same with 9 micron and then with 3 micron, there should now be an almost perfect surface there, nearly totally clear and shiny, at last I polish with Novus no.2 and the shine and clearness is there, then treat with Novus no.1 or treat it with a car wax.

When sanding use tap water and keep wet all of time, clean off with tap water between changes to smaller microns and let dry before Novus no.1

The cover for my BG 1000 came out nearly perfect and the cover for my BG 4002 perfect. with deep scratches present count 2.5 to 3 hours hard work.

Collecting Vintage B&O is not a hobby, its a lifestyle.

sonavor
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sonavor replied on Mon, Feb 15 2016 5:08 AM

Yes, it sounds like the slow, hand sanding process is the way to go. I will also need some good music playing while I sit there and sand the cover. I should be able to manage that part.

Thanks Søren.

sonavor
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While I continue the slow learning process (slow for me) of restoring the dust covers, a new workbench toy arrived today. I have been anxiously waiting to try this new measurement device since I first saw it on Beolover's Blog...the Beogram RPM Calibration Device.  It is so much easier to use and way more accurate than other devices I have tried. With the speed adjusted as close to 33.333 as I could get, it was reassuring to see that the Beogram 4000 strobe indicator was perfectly steady as well.

The RPM Calibration Device came with a couple of other mounting pieces so I can use it on Beogram 800x turntables as well as my 400x turntables.
Very nice tool from Rudy I must say. Great job.  Now it's time for me to put it to use.

 


Beolover
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I just uploaded a video demonstrating the capabilities of the BeoloverRPM device. Enjoy!

Rudy

 

http://beolover.blogspot.com

http://beolover.com

sonavor
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After a few weeks of on again, off again playing around with the dustcover polishing I think I ended up with a decent result. I still need to perfect the technique and I am way too slow. I think I could have restored four or five turntables in the time it has taken me to finish my first attempt at a dustcover.

During my testing I tried several wet sanding paper products. Micro pads, micro cloth and regular wet sandpaper (from 400 grit down to 5000 grit). I did learn it is worth buying some nice, soft, sponge pad sanding blocks. Here is a picture of some of the sanding tools I tried.


sonavor
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On this first dustcover I decided to only attempt the restoration of the top of the dustcover. I didn't touch the sides or the inside of the cover.

I ended up going through all of the micron sanding pad/paper steps, then I restarted back a 400 grit wet sandpaper because I was unhappy with the first result. After that first attempt the dustcover lid was not clear at all. I didn't have the sponge pad blocks on the first attempt though.

I spent way more time on each step the second time around and I used the sponge pads. I also primarily just stuck to the 3M wet sandpaper.
The results were better and the following picture shows the result after the final 5000 grit sanding. The picture actually makes the dustcover result look better that it is. When I look through the dustcover sides in comparison to the top, the difference is very noticeable.


sonavor
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Since I had exhausted all of the sand paper grit steps and the finish wasn't satisfactory, I moved on to the polishing step. The result of the sanding was an extremely smooth surface so that part of the result was good.

I have the Novus plastic polishing products but I decided to try the Glass Polish Plastic Scratch Repair & Polishing Kit. Their video looked pretty good and I figured I might as well try it. Since I had already done all of the sanding steps and my dustcover surface was smooth, I went straight to the final polishing step of the Glass Polish kit. Per their instructions, I made sure the felt polishing pad remained wet (first with the polishing compound, then with water).

The result of the polishing was a big improvement.


sonavor
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Here is a side by side comparison of the dustcover after the final 5000 grit sanding step versus the polishing step. The improvement in clarity is obvious. If I can improve my technique and skill with the top of the cover I hope to eventually tackle restoring the inside of these dustcovers. I have a few with scratches on the underside. I also have some Beogram 8000 and 8002 covers I would like to try...but I am nowhere ready for those types yet. 


sonavor
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Here is some additional information about the various sanding material. The numeric value of the abrasion (i.e. 400 grit) is not the same across the various materials - Micro-Mesh and sandpaper. Here is a conversion chart that shows the differences. The chart doesn't cover the 2000, 2500, 3000 and 5000 grit 3M sandpaper that I finished with though.


sonavor
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sonavor replied on Wed, Apr 27 2016 12:16 AM

Beogram 4002/4004 DC Platter Motor Restoration

In a recent Beoworld repair thread, Martin (Dillen) was kind enough to enlighten us repair students about some key information regarding the Beogram 4002 and 4004 DC platter motors. Those thirty to forty year old motors cannot be lubricated by just adding some drops of oil. The two bearings (one top and one bottom) need to be reinfused with oil via pressure (as in a vacuum). This isn't something many people are set up to do themselves. I fall into that group that is not setup. Our friend, Beolover, fortunately is set up and has made an excellent instructional video on the repair so I thought it would be good to add a link to that tutorial on this Beogram 400x thread. So to launch the tutorial you can just click here.

Thanks Martin and Beolover for your contributions.

-sonavor

RogerGustavsson
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Do you have a service manual or schematic covering that RIAA-board?

 

RogerGustavsson
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Wrong posting, not familiar to the forum.

sonavor
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sonavor replied on Sun, Jul 31 2016 9:04 PM

RogerGustavsson:

Do you have a service manual or schematic covering that RIAA-board?

 

Yes, I have the original service manual for the Beogram 4002-6000 (Type 5501-5502) with the addition of the Type 5503. It has sections in the manual that cover the CD4 board but I have not yet had any of the turntables with the RIAA board on my workbench yet. I think those are pretty rare in the US.

The Beoworld service manual collection (requires at least a Silver Level membership) has the Beogram 4002 Type 5501-5502 service manual  in PDF format that includes the CD4 board.

-sonavor

RogerGustavsson
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About the platter bearing.

I have a Beogram 6000, type 5502, serial no. 261062. When I started to look for a Beogram turntable, it was the 8002 I wanted. Informed myself on the differnet Beogram and came to the conclusion, it is the 4000-series that suits me, the one with a built-in CD4/RIAA, AC-motor and the heavy platter/thicker spindle. I had two to choose from, both in Denmark. Even let a fan of Beogram, Jørn Thøgersen,  inspect one. Finally, I bought one from Odense (Radio og TV Eksperten), they even gave me a warranty.

After arrival, I started an inspection and the play of the platter surprised me. Jørn told me this more or less typical. Tried some PTFE grease at the bottom but I did not help. Now, many months later, I have taken out the bearing housing to inspect it further. This is the auto-centering bearing. It is really the opposite of what is now the norm, a tight bearing with zero play. Yes, there is only a sinter bronze bearing at the top and the spindle rests on a dished plastic plate at the bottom of the housing.

A picture of the bearing.

The bearing with the inner platter.

Of course, I would like to have the bearing housing with two sinter bronze bearings. Is there any place to get one? Classic Audio in Denamrk?

I have decided not to use the built-in CD4/RIAA.

It really looks like a mess and a more modern RIAA could take its place. Nice to see that Rudy Schlaf has one into a 4002. I will probably use one of my own. Need to cut off an unused part of the PCB to have fit inside the Beogram 6000.

ALF
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ALF replied on Sun, Dec 11 2016 2:03 AM

Hello john,

a remarkable post indeed !

It may now all be part of history, but I suffered the same trouble once, failed in the rcovery of that connector and simply resorted to a whole arm-transplant from a 4002 model - worked like a treat and still performs nicely !

That was in the end a much easier exercise  :-)

Now off - again or still - to the dreadful servo adjustment procedure after breathing-in some new confidence from you post.

Wish me luck and patience !!

Cheers ALF

Jim Carr
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Sonavor,  I just found this thread and have a question about your 4002 type 5503. The picture of the main board on the first page shows 2 caps on the back of it. Yours is the second one I have seen like this but mine only has one across TR23. Can you tell me about the second one?

Thanks, Jim.

sonavor
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You are referring to the picture on this page of this thread, right?  The original capacitors shown there are undocumented in the service manuals that I have been able to find. Here is a diagram from my service manual. It shows two versions of the main board depending on the serial number of the Beogram.


sonavor
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Note that the capacitors that were originally on the board were tantalum type capacitors so they are polarized. If you replace them with polarized capacitors (electrolytic capacitors) then you must make sure of the positive and negative lead positions.


sonavor
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I replaced mine with non-polarized, WIMA MKS type capacitors. One capacitor is 1uF. The other is 4.7uF. Due to the size of the 4.7uF capacitor I placed it on the component side instead of the trace side.


sonavor
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Here is the location on the schematic of the two added capacitors (shown in red).


sonavor
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Regarding Beogram 4002 model types. I found this information. Note that the 5502 isn't listed but that is because it was the Beogram 6000.


Jim Carr
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Sonovar, Thanks for the information. Those are the caps I am asking about. My deck is 4002 type 5503 # 295262. I bought it used in 76 while I was a service manager at a stereo shop in Ann Arbor MI. I have the original schematics that came with it and they do not show the one I have ether. I downloaded the service manual for the type 5501 and have been using that to service it. I've done a complete recap and it works great except for the intermittent tone arm issue I am working on.

Thanks, Jim.

 

.

sonavor
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sonavor replied on Fri, Jan 6 2017 8:04 PM

I bought my first Beogram 4002 in the Summer of 1976 as well (when I was in college). It was a demo model in the local stereo store. I got it along with a Luxman L507 amplifier and a pair of Yamaha NS-670 and NS-690 speakers. I had to sell the Beogram and the NS-690's later to pay for school. I can't remember if mine was a type 5503 or 5513. I graduated a year later and the first thing I bought was another Beogram 4002 (type 5523) which I still have.

Regarding your tonearm lift problem, can you monitor it with a digital oscilloscope and try to catch the event? I would look at what the voltage is doing on the solenoid. Maybe it isn't able to keep the solenoid engaged. I haven't looked at the 5503 in a while but on the Beogram 4000 there is a switch that opens up when the solenoid moves that engages a current limiting resistor in the circuit so the solenoid isn't drawing full current (like it does when it first gets the command to lower the tonearm). Maybe that steady-state voltage is unstable on your Beogram 4002 solenoid.

-sonavor

Jim Carr
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Sonavor, I have a thread going about the tonearm so I can respond there to keep your thread on track.

Menahem Yachad
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John

This article was magnificent. I have been so busy that I haven't been on BeoWorld for just about 2 years - right about the time that you posted this.

You have far more patience than me for putting together this type of information, in such a clear and readable manner.

I have so much good info in my head, but very little motivation to put it down in the way you did!

This could be the new BG400x Training Manual.

 

I'm now just about finished my 3rd BG4000 - came out of a flea market for $50, in terrible condition.

A very "small" thread is up, but not in your style!

 

Just so you all know - a local shop in Israel rebuilds the B&O "C-core" flat transformers - has been doing it for decades, and I have used them a couple of times. Having said that, I do prefer the toroid types - much less winding "loss", and more efficient electromagnetically.

Previous BeoWorld thread on C-Core transformer rebuild

 

Kudos! Kudos! Kudos!

Menahem

sonavor
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sonavor replied on Fri, Mar 3 2017 4:20 PM

Thanks Menahem, I am glad it was useful for you.

Wow, a Beogram 4000 flea market find for $50. That is a great find. I'm glad you are saving it.

Interesting information on the transformer. As my 400x post describes, I found one place here in the US that looked at repairing/rewinding the original but couldn't get past the epoxy B&O used in the original transformer. They said it made restoring it impossible for them. It sounds like the shop you found in Israel has a solution for that. They might be an option for me in the future but I wonder about the shipping cost to and from Israel. 

John

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