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
Jacques
That is off a Beogram 4002 type 550x (AC motor type), right?
For the phono cable rewiring, is this wiring information correct? The picture below shows the current RCA plugs and cable I will be replacing.
sonavor: That is off a Beogram 4002 type 550x (AC motor type), right?
No, Beogram 4000!
Here from my 1202, the wire colors seams to be the same, I dont see chassis ground in your pic.
Collecting Vintage B&O is not a hobby, its a lifestyle.
Here's a better angle and the wiring is now (before changing the cable).
chartz: sonavor: That is off a Beogram 4002 type 550x (AC motor type), right? No, Beogram 4000!
Interesting. So B&O updated to that bearing during production of the BG4000 and that carried over to the early BG4002 (AC motor types). Later, they moved to a different mounting for DC motor BG4002 decks it seems.
sonavor: chartz: sonavor: That is off a Beogram 4002 type 550x (AC motor type), right? No, Beogram 4000! Interesting. So B&O updated to that bearing during production of the BG4000 and that carried over to the early BG4002 (AC motor types). Later, they moved to a different mounting for DC motor BG4002 decks it seems.
There is a third type actually, with the same spindle and yet another bearing housing!
Good news, the problem is just the current cable. I connected up the BG4000 to a preamp again and ran my own wire from the turntable to the preamp chassis ground. No hum at all now. The turntable sounds good with an MMC 6000 cartridge.I'm back to another tracking problem though. Actually, it is one that I was seeing earlier. While playing the record, if I raise the tonearm with the up cueing control, I can see the tonearm raise and move slightly towards the start (to the right when viewing from the front). That means it doesn't cue back down to the position it was at. I checked the cueing up and down when nothing is playing and it goes straight up and down during that action. That must mean there is something still off with the diaphragm adjustment. Before I hit the cue up button, the tonearm visually looks like it is perfectly parallel with the detector arm so I'm not sure what moves it to the right.
Tonight I rewired the Beogram phono cable. The existing one had been modified. It is too short and it has some cheap RCA jacks. I am going to install a two conductor plus shield main cable, then cover it with an outer shield wire, then cover that with a braided outer insulation. For the amplifier connection, I will re-install a 5-pin DIN jack. The inner cable shield will carry the Left and Right channel low signal to the DIN jack pin 2. The Left high signal will be one conductor and connect to the DIN jack pin 3. The Right high signal will be the other conductor and connect to the DIN jack pin 5. The outer shield will connect to the Beogram system ground and to the DIN jack case. This cable configuration will match how my Beogram 4002 type 5503 phono cable is set up.Here are the new phono cable connections and system ground (outer shield) connected to the Beogram.
Here is a picture showing the new phono cable as it comes out of the Beogram.
Here is the amplifier connection side of the new cable in its raw, unfinished state.
Here is the old and new cables side by side. The next time I make one of these I will use a smaller gauge audio cable. With the inner cable and outer shield, the rubber boot of the DIN plug could not fit back into the metal housing. So I had to use heat shrink to button everything up. It still looks better than the old connectors and it will work great.
I tested the new cable by plugging it into the phono connection of a Beomaster 4400 I use in my workshop. It plays perfectly...no unwanted hum what-so-ever.
I had really hoped that I would be putting this Beogram 4000 into service in one of main stereo systems this weekend but in studying the turntable playing a record on my test bench, I can see that the servo control for the tonearm is still not adjusted correctly. The servo isn't advancing as often as it needs to so that is causing the pause (cue up) to result in the tonearm swinging slightly back from its playing position.Most everything else is adjusted now except the differential stop adjustment (4-8), Height and Side Adjustment of Chassis (4-1) and the strobe adjustment (4-2).Here is the differential stop adjustment procedure. I must confess it is a little cryptic to me.
Are you sure the carriage belt is not too tight?
I wondered why I couldn't get the worm screw to turn at every revolution of the platter and Martin gave me the solution. Too tight a belt and the arm will move in little jerks, not smoothly as it should.
Perhaps this is your issue too?
Small jumps as in 1/4-1/2 revolution of the spindle is about as good as most decks can get.Jumps of 3/4-1/1 revolution will also be fine.You will hardly ever see a constant slow revolution in any of these decks.Martin
chartz: Are you sure the carriage belt is not too tight? I wondered why I couldn't get the worm screw to turn at every revolution of the platter and Martin gave me the solution. Too tight a belt and the arm will move in little jerks, not smoothly as it should. Perhaps this is your issue too?
Thanks Jacques, I really owe you now! I was about to stay up all night trying to make the adjustment and was getting nowhere. Taking your advice, I removing the tonearm motor belt completely and gently kept a finger on the motor pulley to detect when it started to turn. That yielded progress. I started to find where the motor turned and could see the number of platter rotations go down as I made adjustments (between each test). Putting the belt back on would go back to 12 - 14 turns (or more) before any movement would occur. That was because, as you suggested, the belt is too tight. Prior to that I was stuck in an endless loop. I did find some bad spots in the 100 ohms trim pot during my adjustment attempts so I replace it with a new one.I opened up my Beogram 4002 type 5503 and stole the tonearm motor belt out of it to try in the BG4000. Now I am able to get the diaphragm adjusted. The strange thing is, yesterday I was able to get the tonearm to move at 4 turns of the platter so I thought all was well. It wasn't until much later, when I tried to play a record for real, that I noticed the cue up was pulling a little. That happens when the tonearm motor doesn't start responding within that 3-5 turn range.Now I need to find some good Beogram 400x tonearm belts. I probably should get a few spare platter belts as well. Martin has been out of stock on those for a while so I need to find a good second source.
Dillen: Small jumps as in 1/4-1/2 revolution of the spindle is about as good as most decks can get.Jumps of 3/4-1/1 revolution will also be fine.You will hardly ever see a constant slow revolution in any of these decks.Martin
I just finished some test playing of a record and the cueing is working perfectly. No loss of position due to slow tangential tracking start up now. There is one concern I have going forward with this turntable. I noticed lately, while switching cartridges to do testing, that the cartridge connector on the tonearm isn't as solid as I would like. It seems a little weak and I am worried that it might break one day. I guess the only thing to really do is put a favorite cartridge on and leave it alone. Earlier tonight I tried to install an MMC 20CL cartridge on the tonearm but there was too much resistance trying to install it so I abandoned it in fear of breaking something. I am going to leave the MMC 6000 on for now.
Yes, it is a known flaw. Tim mentions it in his June '14 Hifi News feature about the 4000.
chartz: Yes, it is a known flaw. Tim mentions it in his June '14 Hifi News feature about the 4000.
I checked old Beoworld threads and found this thread that talked about the problem. The solution there was replacing the whole tonearm. I couldn't find the Tim Jarman article. Was it just a report about the problem or does it have solutions?
He said there was no fix. But then, I'm sure that Rudy will come up with something involving 3D printing!
Is the problem just that the plastic tab becomes weak and breaks?
Yes.
Well, after all of that, my Beogram tonearm is indeed suffering from the cartridge tab disease. I decided to examine the cartridge mount again this morning and it is weakened beyond use. In fact, I noticed the bottom of the MMC 6000 cartridge was not secure. It could move. Looking closely at the top part, I could see the black plastic tab had separated to the cartridge was just held in place by the flat, metal contacts. So that is a nice setback on this project as I'll have to search for a replacement tonearm. I remember on the Beogram 8000 turntable that there isn't really a way to repair a damaged cartridge connector. Those are glued into the tonearm and don't appear to be intended for repair. To make matters worse, I think I will have to send my cartridge in to Benny or Axel to get the broken tab out. I don't want to risk damaging the cartridge.
C**p!
Ask Rudy then. He seems to be very imaginative.
CAUTION - This post contains images that some people may find disturbing
Here is the ugly reality.
OMG
Dip the tonearm tip in boiling water and pull out the remains of the broken socket.
Martin
sonavor: CAUTION - This post contains images that some people may find disturbing Here is the ugly reality.
Indeed shocking and I understand your frustration, doing a perfectly good job, and then a setback like this. But we never give up. Here my idea to retract the plastic tap
Heat the point to about 400°C press it into the plastic, let cool, pull out the tap, heat again pull off the tap and clean the tool
Dillen: Dip the tonearm tip in boiling water and pull out the remains of the broken socket. Martin
That will loosen the bond so the plastic mount will come out? So I can do that with a spare arm (like from a beat up 4002 or 4004) to get a replacement mount?
Wow...bummer! This is a sad setback! I have a 4004 where the connector is loose, so it definitely can come out. With regards to reproducing this, I think it is challenging. Maybe a combination of a printed part with a small circuit board that has the right thickness and the 4 connectors on it might do it...I am wondering if one can bend FR4 to the right angle when heating it...
Rudy
http://beolover.blogspot.com
http://beolover.com
Working with the Beogram tonearms removed will require special care to not break the phono cable from the arm to a small board on the tangential arm transport. When I'm ready to remove the tonearm and try the hot water treatment, I'll have to unsolder the wires and pull them through.Here is where I have traced the phono signal to on the transport board.
A few days back I was complimented on doing a good job on this Beogram project. I mentioned that I couldn't do it without the help of the Beoworld folks that help guide me along the way. Yesterday and today are perfect examples of that. Last night I was stuck trying to figure out the problem with the tracking adjustment when, Jacques sent me a message about it being a belt problem. Sure enough, that was the problem.Today, I seemingly ran into a giant road block with the tonearm cartridge mount. Martin stepped in and gave me an amazing tip on removing the plastic cartridge mount insert from the tonearm. Amazing! ...and a huge thanks!I had messed around with a Beogram 8000 turntable last year that had a broken phono cable. The plan was to replace the cable but I was stuck with the removal of the plastic cartridge mount. So today, I used that arm to try out Martin's amazing repair tip. Sure enough, after submerging the arm (remove from turntable first ) in a pot of boiling water for a minute or two, I was able pop the cartridge mount right out (using a long screw driver to push from the opposite end).Here is a picture of the Beogram 8000 tonearm and the cartridge mount removed. I can probably use that piece as a replacement for the Beogram 4000 tonearm or I also have a Beogram 4004 parts unit I could use.
Awesome!! Never give up! What a nail-biter!...;-)
I always seem to run into some technical drama on these projects. I guess that is what makes it fun.Here is a better picture of the Beogram 8000 tonearm cartridge mount. I will try to carefully get the broken one out of the Beogram 4000 later to compare. The mounting assembly is really two pieces. It looks like it could be a candidate for a 3D part substitute in the future.
Here is the Beogram 8000 cartridge mount opened up into its two, clamshell pieces.
Removing the Beogram 4000 tonearm should be a little easier than I originally thought. Flipping the tangential arm transport over, the cable from the tonearm tranfers from the tiny phono wires to heavier wire for routing out to the mute relay and out to an amplifier. So I can un-solder the tonearm wires there and detach the tonearm from the pivot mount. I will try not to break the phono wires so I can re-use them. It might be inevitable that I will need to change the wires though as it is going to be tricky not damaging them when I push the cartridge mount off the tonearm.