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Beogram 8000 Project

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sonavor
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I have been wanting to work a Beogram 8000 restoration project for over two years now but kept getting derailed by other things. Now that I have several Beogram 8002 projects under my belt and a few Beogram 400x projects finished, it is time to get at least one Beogram 8000 turntable working in my home.

Two of my Beogram 8000 turntable candidates were from system purchases I made over the last two years. A third turntable is one I found for a good price on Ebay.

All three BG8000 turntables were acquired in non-working condition. I also collected some of the Beogram service and technical manuals so I think I am ready to start.


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sonavor
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I had to order a few 2200uF, 16V and 4.7uF, 100V capacitors as well as some 40 pin DIP sockets (to replace the old ones for the microprocessor). Everything else I had plenty of stock so I am ready to start working on the first Beogram.  I think I will restore the newest serial number turntable first as it has all of the factory integrated modifications.

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sonavor
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Now on to the hardest part of a Beogram 8000 (or 8002)...the lid. This is the only part I don't like about repairing these great turntables. The dust cover is a real pain to work with. Especially compared to the Beogram 400x series. Those are so nice.
Here is a series of pictures showing hinge attachment. It usually takes me several tries to get everything to line up and click into place. I am always tempted to install some screws in the back of the lid panel to tighten everything up but so far I have always been able to get the lid snapped back together.


sonavor
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One reason I ran the rumble tests on the Beogram 8002 was I pulled it from my 8000 system so I could install this new Beogram 8000 in its place. The original owner of this 8000 system did have a Beogram 8000 and MMC-20CL with his system so now they are back together. My Beogram 8002 will quickly find a place somewhere else in my house though. It is my best 8002 turntable and the one I originally purchased new back in 1983.

Here is the Beogram 8000 in service again. I started it out with side 2 of Led Zeppelin II.  It sounds as if the Beovox MS-150 speakers were made just for that album.


pfcs49
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pfcs49 replied on Thu, Jul 30 2015 5:28 PM

Well, it's nice to hear that somebody else has considered screwing the damn back cover!

So far I've been able to find useable ones, but the darnn plastic seems to suffer from age embrittlement and it's hard to not break the clips.

Lately I've avoided removing them by pushing the hinge "pin" (a long steel wire actually) out and removing the covers before opening the clamshell main case. This seems a much more manageable arrangement to not have the dustcover flying up and around while dealing with everything else that sucks when opening these units!

sonavor
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Suggested by pfcs49

pfcs49:

Lately I've avoided removing them by pushing the hinge "pin" (a long steel wire actually) out and removing the covers before opening the clamshell main case.




What is your technique to remove the pin?  I might want to do that on some of these covers that will need re-surfacing and re-polishing.

-sonavor

Lee
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Lee replied on Fri, Jul 31 2015 1:56 PM
Seconded. I would like to know how to remove his pin for this same reasons.
pfcs49
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pfcs49 replied on Tue, Aug 11 2015 11:27 PM

You only have to push the rod out a little way before you can clamp mini-vicegrips to the other end and pull it out.

It goes back pretty easily if you un-weigh the hinge while twisting and pushing it.

This makes re-assembling much easier and until the hinged covers are reattached, it's easy to open if there's a last minute issue.

(I usually work with the covers and upper housing off, the "guts" exposed, with a towel under the electronics board to prevent any shorts, keyboard and transformer plugged in. This way it is easy to confirm all functions are good to go before really assembling anything.)

Beobuddy
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sonavor:

I have now resoldered all of the main board connectors and switched out the two 1uF capacitors that were mounted on the trace side. There are now just a couple of capacitors to check on the chassis before I can reassemble the turn table for a check of the board reword. If that goes well I will be able to start in on checking the tangential arm assembly.

 

Hi Sonavor,

 

I have here a BG8000 without the 1uF capacitors. So I took a closer look at your pictures. I think the capacitors should be mounted from ground to the optical risistors R9 and R10.

Is it possible that you've mounted the Wima's the wrong way?

As I think it should be one mounted between pin 3 (ground) and pin 6 (optical right resistor R10), and one mounted between pin 3 (ground) and pin 4 (optical resistor R9) . Both your Wima's are soldered on pin 6 from P5.

I have both original diagrams/manuals from the BG8000, but there aren't capacitors accros R9 and R10 mentioned. Is there a supplement of this?

sonavor
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Beobuddy:

Is it possible that you've mounted the Wima's the wrong way?

As I think it should be one mounted between pin 3 (ground) and pin 6 (optical right resistor R10), and one mounted between pin 3 (ground) and pin 4 (optical resistor R9) . Both your Wima's are soldered on pin 6 from P5.

I have both original diagrams/manuals from the BG8000, but there aren't capacitors accros R9 and R10 mentioned. Is there a supplement of this?



I rechecked the pictures of the original capacitors and my recapped Wima 1uF replacements and sure enough, one of my Wima caps is across the wrong pins of P5. The one on the left correctly goes from P5-6 to P5-3 but the one on the right should go from P5-4 to P5-3 as you say. The Beogram 8000 Service Manual shows them on page 1-4 in the diagram of the Control Circuits, 8005040 PCB (foil side). This is from the Beogram 8000 Service Manual 3538483 02-81. The two 1uF capacitors look hand drawn but they appear to be hand drawn on the master copy. Here is a picture of my service manual. I am just about to start a project where I will be working on four or five Beogram 8002 turntables and another Beogram 8000 so I'll have to pull my Beogram 8000 and switch that capacitor.

Thanks for catching that. You definitely are a Beobuddy Smile

 


Beobuddy
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Thank you.

 

I've looked at my service manual and indeed there are these "unofficial" small drawings. Didn't notice them.

These are marked as "C12"and "C13" on the diagram I see.

But it's strange that "mine"BG800 here doesn't have these caps. BTW I think it doesn't make a difference if you just use ordinairy caps instead of the Wima's . These are just there to stabilize any fluctuations in R9/R10 which could cause nervous behaviour from the motor.

 

But thanks for sharing all the pics. Back to my own problem....instable speed despite new made tacho disk (done by former technician with glossy black/whte paper printed)

Just a question. If you're able to help me with an answer for it. What frequency should be measured on P6-2 during 33,33 rpm? It'comes from the tacho sensor. Maybe the tinkered tacho disk isn't that succesfull.

 

Thanks in advance.

sonavor
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Beobuddy:

But it's strange that "mine"BG800 here doesn't have these caps. BTW I think it doesn't make a difference if you just use ordinairy caps instead of the Wima's . These are just there to stabilize any fluctuations in R9/R10 which could cause nervous behaviour from the motor.

 

But thanks for sharing all the pics. Back to my own problem....instable speed despite new made tacho disk (done by former technician with glossy black/whte paper printed)

Just a question. If you're able to help me with an answer for it. What frequency should be measured on P6-2 during 33,33 rpm? It'comes from the tacho sensor. Maybe the tinkered tacho disk isn't that succesfull.

 

Thanks in advance.

I agree, I went with the Wima caps on mine because I had them in stock, they are easy to use and they have a long lifespan. But if I didn't already have the Wima caps I wouldn't hesitate to use the electrolytic caps there.

I will have to get my Beogram 8000 back on the bench to get the frequency measurement at the speed sensor pin (P6-2). Currently my bench space is being populated by a disassembled Yamaha preamplifier but I might be able to get to the Beogram this weekend.

Dillen
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Dillen replied on Tue, Sep 8 2015 10:10 PM

Beobuddy:

...instable speed despite new made tacho disk (done by former technician with glossy black/whte paper printed)

You cannot print a decent tachodisc.
It's simply not precise enough.
Even B&Os own photographic type had jitter.

Martin

Beobuddy
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Beobuddy replied on Fri, Sep 11 2015 10:12 AM

@ DIllen/Martin: You are absolutely right!

 

I've changed the special made disc (which did look very trustfull/reliable) with the one Martin provides. And the result is a very stable BG8000. Yes!

FYI: frequency measured at P6-2, tachosignal from the disc, is 83,33hz.

The frequency measured at P4-4 is 50hz.

So, if someone doubts his sensor or drive......

sonavor
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sonavor:

A closer look at the modified board shows that the Periodical Variation of Turntable Speed fix was added on versus the other Beogram 8000 where the change was more integrated into the microcomputer board (from the factory).

In response to Alf's question about the red and blue wires attached to the positive and negative leads of the C28, 47uF capacitor...
The C28 capacitor is for +5 VDC to the integrated circuits on the microcomputer board. There is also the little daughter board containing an HEF4013B dual D-type flip-flop. To get power for that chip the red wire supplies +5 VDC and the blue wire supplies the return (ground). Some of the Beograms have the HEF4013B tap into power as in your picture, directly across the capacitor. Others get the same power and ground from other (nearby) connections on the microcomputer board. The flip-flop was a modification to the Beogram 8000 and you can read about it here

Regards,
John

 

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