ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
When I went to re-attach the Beogram black, plastic arm cover I noticed that there is a slight difference between the earlier Beogram 8000 units and the later serial number turntable I am restoring. The later serial number turntable has a notch that is necessary for a small tab in the tangential arm assembly not on the earlier serial numbers.
The Beogram deck is now prepared for the metal cover. I am waiting on the Goo-Gone to do its job on the old tape underneath the metal deck before can attach it to the deck.
sonavor: Jacques, the tonearm lowering appears to lower at a nice consistent speed. A couple of times it appeared to be a little faster drop but I will have to run some more tests once I get the Beogram suspension in place.
Jacques, the tonearm lowering appears to lower at a nice consistent speed. A couple of times it appeared to be a little faster drop but I will have to run some more tests once I get the Beogram suspension in place.
I could not find the Teflon bit that Martin mentioned. My two BG are affected.
Jacques
I couldn't find the Teflon piece either. On the next Beogram 8000 I will monitor the arm lift signal on my oscilloscope and see if it is the same every time the tonearm lowers.Meanwhile, I am still trying to wrap up this first BG8000 turntable. I have the deck on and the platter height adjusted. It took several tries of removing the platter and adjusting the suspension spring screws until the platter was flush with the deck.
I connected the Beogram to my bench Beomaster 4400 for a listening check (this time with the Beogram suspension in place). No problems my ears could detect.
I currently don't have my test bench set up to run good turntable tests with my spectrum analyzer. I should have everything I need to set the tests up but I just haven't got organized properly to perform them. I would like to be able to run repeatable tests between various turntables where comparing the results are meaningful. I bought a stand alone preamplifier that I thought I might use (pictured below). It might be okay but when I connect it to the spectrum analyzer I see a 60 Hz line component. It is down below -90db but my Yamaha C2a phono preamp has no 60 Hz component and its noise floor is way below this one. So I'll have to figure out something regarding my own turntable/cartridge bench testing.
Just to try though...here is what my analyzer reads from the Beogram 8000 (MMC-20CL) using B&O test record 3621003 track 9 - Rumble Test (silent groove). The phono cable is going to the JEC preamp and to the QuantAsylum USB box.
I've been doing some reading up on turntable measurements. Some test records have tracks with tests that rely on human hearing to evaluate the results. That is reasonable and easy to perform but of course not entirely accurate (depending on the type of test). Rumble measurements with silent passages on a record and measured with a spectrum analyzer are interesting as there could be rumble artifacts from the recording process. Frequency measurements are more suited to testing with an analyzer but the cartridge becomes the main focus of those tests. I think the best course I can take for my own testing is to find a good set of tests that I perform the same way every time and collect my own set of reference data. That data can then be compared using my own hearing as a reference...meaning I should be able to look at the analyzer data between a turntable/cartridge I think is really good and compare it to ones I think might be off.
For this Beogram 8000, I have now listened to several albums through the Beomaster 4400 and a pair of Beovox S55 speakers in my workshop. I am pleased enough with the sound to wrap up this turntable and put it in with my Beomaster 8000 system (replacing the current Beogram 8002/MMC1 that is there). All I have left is to choose the best lid/dustcover and re-attach it.
-sonavor
I couldn't resist running some more rumble tests. Looking at my results again, the measurements don't look too bad. The frequencies with the highest levels are down around 10 Hz which is what you would expect. This picture shows the analyzer results for the Beogram 8000 (MMC-20CL) playing the B&O 3621003 test record rumble track. The top part is un-weighted and the lower part is "A"-weighted.
This is the same test setup but with a Beogram 8002 (MMC1). It appears that the rumble measurement is a little bit better with the Beogram 8002 and MMC1 cartridge. These are just the first two measurements. From now on I am going to start collecting the same measurements anytime I have one of my Beograms on the bench and then see how they compare.
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.
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.
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!
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.
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.
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.)
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.
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?
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?
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.
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.
Beobuddy: ...instable speed despite new made tacho disk (done by former technician with glossy black/whte paper printed)
...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
@ 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: 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).
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
Can You send a picture of where the teflon pad sits?
Jenku
Are you referring to the pad for the dust cover hinge as pictured at the top of this page?
Yes I am.
I found it floating around in the bottom of the case.
I can't find any marks on the plastic wall where the teflon used to be due to a lot of grease added by the previous owner.
So is the plate going to sit right op to the bend or way down?
Regards
jenru
The second picture on the previous page has an arrow pointing to the plastic/teflon sheet and where it goes. If there is grease in there you will need to clean it off (alcohol) and glue the teflon sheet back in place.
Ups! I thought that the square piece 1x1 cm. mentioned was the teflon plate.
Now I know better.
The metal piece is inseted in the cover hinge for the small end of the leaf spring to lay upon.
Regarding the Back Part (From the Service Manual: item 003, Part Nr. 3030067) Dillen advised me to glue it to the frame which I did.
Because one never need to take it off.
Cut out a small corner of the back part and you can remove the pin that hold the lid.
How do I add Pictures to my answers???
jenku: How do I add Pictures to my answers??? Jenku
A couple of ways. If you have just one photo you can use the Options tab in the Reply screen to Add a photo from your computer. There is a size limit though.Another way is to go to your Beoworld Profile and use the My Files section to create folders for uploaded photos. Once the pictures are uploaded there you can use the Insert Media icon on the Reply editor box to insert multiple photos (from your My Files section) to the reply.-sonavor
Thanks for the quick answer.
By the way, where can I find out what kind of tape on the backside of the keypad protects the cobber contacts?
Or can I use plain electrical tape:
Jenru
jenku: Thanks for the quick answer. By the way, where can I find out what kind of tape on the backside of the keypad protects the cobber contacts? Or can I use plain electrical tape: Jenru
You don't want to use electrical tape or similar plastic tapes. They are too thick. It is best to leave the original tape but if you are in a fix where you absolutely have to replace it then I have used a thin foil tape. Something very thin. Maybe around 3 mil. in thickness. If someone knows of an equivalent tape to what Bang & Olufsen used I would be interested in getting some as well. The tape is there to prevent dust from getting inside the contacts but has to be thin enough to allow the buttons to actuate the contacts.
Hey again
It's funny that the tape is there to prevent dust from getting inside the contacts cause it can enter from the othe side through the small gaps for the contacts legs.
There was no tape on six of the contacts neither tracks of any tape so I found some laying around and added some strips.
In the picture it' the lighter tape to the right and the contacts are working flawless.
As You can see, the is so thin that one can se the PCB tracks.
jenku
It looks like your image didn't insert into your post.
Ok I try again.
If the picture is not present this time I don't know what i'm doing wrong.
Rigt now I'm looking at it (8X6 cm), placed in this reply.
And taking a closer look I also found out where the little square piece of metal and the teflon piece sits.