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I have a Beogram 4004 which I haven't used for many years. I took it out of storage the other day and tried to get it going. The tone arm didn't lower, but after cleaning and lubricating and giving the solenoid a little "massage" it worked almost perfectly.
The problem is that the arm doesn't always raise as it should on return. Sometimes it works ok but sometimes the arm doesn't raise before it has travelled 1-2 cm on return.
/riis
I also unscrewed the three leveling bolts and took out the height adjustment bolt. I put it back without paying much attention to the level.
Can this have caused the problem?
Your problem is probably the damper blue arrow in the pic, dismantle it for cleaning and lubricating, Here one thread and here another to study, it is important that the whole mechanism is clean, lubricated and everything moves freely
Collecting Vintage B&O is not a hobby, its a lifestyle.
Hi,Are you saying that when you press the raise tonearm button or the stop button there is a time delay before the Beogram responds and the tonearm raises up? If that is the case then it could require a capacitor kit from Dillen. However, first check the tonearm raise/lower lever. It is attached to the fixed detector arm and fits in the V shaped notch at the rear of the tonearm assembly. When the solenoid activates and pushes that lever, it releases the tonearm. That lever can often start sticking in its pivot point where the lever doesn't move easily. That would cause problems with the arm raising if the lever doesn't pull back down when the solenoid releases. Removing and cleaning that lever pivot is not too difficult but requires quite a bit of disassembly. Checkout this thread and this blog.
The bolts you took out are for leveling the platter and setting its height with respect to the tonearm. Unless you are going to go through all of the service manual adjustments I wouldn't mess with that just yet. I can't seeing that affecting your tonearm raising problem. -sonavor
Here the raise lower lever
No there is no delay when I press the raise tonearm button or the stop button. These functions work ok. The problem sometimes (and only sometimes) occurs when the record is finished playing and the tonearm returns.
Søren thanks for the pictures. Do you mean that I should lubricate the areas marked with blue and red arrows?
riis: No there is no delay when I press the raise tonearm button or the stop button. These functions work ok. The problem sometimes (and only sometimes) occurs when the record is finished playing and the tonearm returns.
Okay, so what you are saying is that there is a problem detecting the end of the record and raising up?
Yes, that's the problem.
riis: Yes, that's the problem.
That is a different issue then. I would say your mechanical linkage is all fine if the normal raise and lowering works via the cueing buttons.With the end of record detection, does it eventually raise automatically...meaning is the problem just that it isn't detecting the stop point where you expect it? Or does it never raise up by itself at the end?Those model Beogram 400x turntables use a plastic scale with black markings to trigger the turntable's tonearm position events. The markings affect a light source to a photo resistor. If the problem is electrical then I would still look at replacing the electrolytic capacitors. If it is a mechanical problem with the scale (and its travel) you would need to observe the tonearm carriage travel with the Beogram opened up to see what is going on. Maybe measure the signals being generated for those events.-sonavor
I understand what you mean, but there is no pattern in the way the tonearn returns. Worst case is that the arm returns to stop without raising. Not very good for record nor stylus. A little better is when the arm raises after travelling one or two cm and then returns to stop. And then there are times where it just works perfectly
I hope you understand what I mean.
riis: I understand what you mean, but there is no pattern in the way the tonearn returns. Worst case is that the arm returns to stop without raising. Not very good for record nor stylus. A little better is when the arm raises after travelling one or two cm and then returns to stop. And then there are times where it just works perfectly I hope you understand what I mean.
I thinks so. If the other tonearm positions are being detected correctly by the photoresistor, for example the start of the record is detected and the tonearm lowers properly, then the problem looks to be in the circuit that responds to the end of record signal. Just guessing but I think that points to the run-off stop circuitry on the main board. Page 5-2 of the service manual lists 1TR16 as a component to check for that type of failure. If you have the service manual and some test equipment I would monitor the components in and around 1TR16 when the stylus is at the end of a record. -sonavor
Thanks very much for your help. I'm afraid I won't be able to solve the problem as I know nothing about the electical parts of the Beogram.
riis: Thanks very much for your help. I'm afraid I won't be able to solve the problem as I know nothing about the electical parts of the Beogram.
I think you have the problem narrowed down to the specific area. Since you are in Denmark I would contact Martin (Dillen on this forum) and see what it would cost to repair it. The Beogram is well worth getting back to full working condition.-sonavor
I have measured the platter height and there is only 20-21 mm from platter to top of the tone arm.
Can this be the cause of my problem do you think. As you can see I'm desperately hoping for a mechanical issue that I can fix to solve the problem :-)
riis: I have measured the platter height and there is only 20-21 mm from platter to top of the tone arm. Can this be the cause of my problem do you think. As you can see I'm desperately hoping for a mechanical issue that I can fix to solve the problem :-)
I have this problem too.
- Arm raises immediately if I press the right buttons on the deck
- Carriage detects end of record and moves back to start
- BUT sometimes there is a delay between the carriage starting to move back and the arm -> needle can be dragged several cm across the record surface before lifting. Sometimes the delay is very short e.g. the arm swings a few mm to the left as the carriage starts moving, before the stylus leaves the record.
This is clearly the wrong order of events! The arm should lift, then after a short delay the carriage should start moving... what with vinyl often being irreplaceable and replacement cartridges for these decks costing $$$...
It's perhaps not an issue with the mechanical raising of the arm, since this responds fine, immediately, every time I press Up/Down or Stop.
It's not an issue with detecting the end of the side or the carriage motion, since the carriage does this fine every time.
So it could be a problem with how the 'end of side' signal gets to the 'raise arm' input, since both functions work fine, independently.
Of course, since the problem is intermittent, it could be that the raise mechanism is a bit sluggish, although this deck was recently serviced by Beolover, and even more recently the various linkages in the lifting solenoid setup were lubricated by myself, during which excercise I could see no problem with the lifting mechanism.
So, question:
- Is anyone familiar enough with the Beogram circuitry to advise on where such a problem might be located? i.e. where do I put the probes of a two-channel oscilloscope to detect the 'end of side' output, 'start carriage return' input and 'lift arm' input, to see if this delay is electronic, rather than sluggishness in the lifting mechanism?
(Given that it's all discrete components, I guess a partial component failure might mean the 'end of side reached' signal, which is getting to the carriage motor system fine, might be being degraded on the way to the 'lift arm' circuitry)
Finally, if anyone is familiar with the circuitry, is there an obvious point to increase a timing capacitor value to make a more obvious gap between 'raise arm' and 'start carriage return'?
It's a known problem - also described in a B&O tech note.It's because the solenoid plunger gets "permanently" magnetized and won't let go when the solenoid power is removed.Instead it hangs up for a varying amount of time.Because you cannot take the plunger out of the solenoid without breaking something (- else you could introducea thin insulating washer inside to stop the plungers physical metal-metal contact),the solution is to replace the solenoid with one from a newer deck.
Martin
Ah, so it happens when the solenoid is pulled in for an extended period (such as playing a record side), but not when the solenoid is briefly pulled in (such as testing/pressing one of the buttons)?
Quite a design flaw!
I wonder if connecting the solenoid to AC for a few minutes (resoldering the wires possible without breaking anything) might demagnetise it, sort the problem out for a bit? What voltage would you recommend for this particular coil?
When it's in the 'down' position, I measure 1.49V across the (10 ohm?) coil. So I'm thinking of de-soldering the live end, connecting it to a small audio amplifier with a signal generator attached, then supplying 1.5V pk-pk @100Hz or so for 30 seconds, then gradually turning the amplitude down to zero.
This may of course not work in removing residual magnetization in the plunger, but more specifically is there anything I'm missing here?... before I do some damage!...
It wouldn't provide a permanent fix.The problem is the metal-metal contact.
Nor would replacing it from a dead 4004? This seems likely to be a problem that gradually worsens over time (years).
Demagnetizing might sort it out for a while.
Anyway, I've performed the following procedure:
- de-solder solenoid at PCB
- attach it to an oscilloscope (to measure voltage across solenoid) & the output of a small audio amplifier
- connect sine wave signal generator to input of amplifier
- from zero, turn up signal generator until +/- 1.5V across solenoid
- push plunger into solenoid
- leave it there for 45 seconds
- gradually turn down signal generator to zero
- disconnect everything, re-solder solenoid
Everything works okay now BUT my problem was intermittent, so initially this proves nothing!
I will report back whether this actually seems to have achieved anything (!) after using it for a while.
(I still think it's nuts that the Beogram 4004, for all its sophistication, can start moving the carriage back to the start when the stylus is still on the record. I know that modifying the B&O circuitry is anathema to a true Beofan, but there must be a simple way of fitting an 'arm up detect' switch to prevent this from ever happening. Any/all suggestions 1. where to fit the switch and 2. where to wire it into the control electronics gratefully received!)
Simple AND circuit? End of record AND solenoid out switch signal to go on.
blah-blah and photographs as needed
And double... There should be delete option on More menu
Undoubtedly
It seems like the best solution is to solve demagnetizing the solenoid. Either through the method you used or figuring out a way to disassemble the solenoid. For the latter it appears that the metal bar that actuates the lever for the arm lowering damper would have to be bent straight so it could be removed (after also removing the lock washer). I have a solenoid right now that appears to have this magnetization issue. It was kind of sticking when it tries to engage...I could feel it resist moving when I had the solenoid out by itself and operated it manually. I checked it out with a DC power supply and it required about 700mA at 7 VDC for the solenoid to engage. Again, that is with the solenoid removed and unloaded. When I tried a solenoid that does not stick and is properly working it only required 300mA at 3 VDC for its solenoid to engage.I am going to see if I can do anything to correct the first solenoid.
-sonavor
Actually...the solenoid components disassembly quite easily.I will post a photo in a little bit.
I made a quick repair and a blog post about it here.
Initially I tried to post the photos here in this thread but I could not get my photos to upload to my Beoworld folders.-sonavor
Nice piece of work. I wish my workshop had spare Beogram parts lying around (!).
Your efforts suggest that removing & disassembling the solenoid is not too tricky. That being the case, I wonder how hard it would be to replace the solenoid liner with something non-magnetic? As long as that remains potentially magenetisable, the residual magenetism issue will keep coming back.
(Alternatively, if my method of 'demagnetization in situ' works - nothing conclusive to report yet! - I suppose one could add a little PCB that demagnetizes the solenoid every time a record is finished, as there is always that 'spare time' when the arm is up and the slide is returning to the 'rest' position at the end of a side)
I did as Martin suggested and added a small washer (nylon M2) to the end of the plunger that makes contact with the sleeve. That should prevent the problem from coming back. Having restored a lot of Beogram 400x turntables and owning quite a few myself I don't think this is a widespread problem. I think it warranted the B&O service bulletin that Martin mentioned but it isn't something every Beogram 400x turntable has. The one I fixed is the first one I noticed an issue on. However, now knowing it can be a problem I will plan on adding an M2 washer to insure the problem doesn't happen on any new projects.
Just a note about the nylon M2 washer...The thickness of those are about 1mm. I found some fiber type M2 washers like are used as insulators for screws on circuit boards. Those washers are 0.5 mm so they might be a better choice. I am going to try that type on another solenoid.
Thanks for bringing the problem to our attention. As I said, it wasn't something I had encountered so it is great to learn something new about restoring the Beogram 400x turntable.
Brilliant! Could you upload a photo, just so as I can see clearly what you did?
I posted the photos here.
I have an update.The M2 nylon washer (that is 1mm thick) does not work. It interferes with the Beogram circuit's ability to keep the solenoid engaged.In testing it I found that the solenoid keep disengaging. I removed the washer and now it works perfectly again.I think I will try out a 0.5mm thick fiber washer (also and M2) and see how that does. However, I am leaning to the solution to this problem being to disassemble the plunger from the brass lever, demagnetizing the plunger and the solenoid metal frame (including the sleeve component for the plunger and the lock ring).
I updated the blog post. The 0.5mm fiber M2 washer also interferes with the solenoid operation by the Beogram 400x circuit. It is best just to demagnetize a problematic arm lowering solenoid then leave the components as they are.
0,2mm electrical tape is ok, do not know if it is any help anyway.
The way the circuitry does the initial 'pull' at 30V then 'holds' at around 3V says a lot for the sensitivity to distance here! I guess it's no surprise that the circuit was designed to hold with zero separation between the components. The residual magnetization issue is considered to be to do with that physical contact, so it may be abolished by much smaller separations, but of course how physically durable would a washer 0.1mm (or less!) be in the long run? So you're probably right about demagnetization being the solution...
Perhaps it would be better if some metal was removed to minimize the metal-metal contact area, rather than fit something in between.
UPDATE. Apologies for the pause, I had to wait many weeks for my MC20EN to be 'renovated' after I had noticeable distortion towards the end of 12" singles. Finally it has returned (and now appears to be labelled 'MMC4000"... the murky world of refurbishment...) and can play the end of 12" singles without distortion.
Anyhoo, I can confirm that demagnetization in situ @ 3V pk-pk, as described above... DOESN'T WORK.
I note that just testing using the buttons all still seems well: Press the button, the arm immediately lifts. However, play a full side of an LP, and at the end of the side it drags the needle - ouch! My just-refurbished $$$ needle! - up to halfway across the LP - Ouch! My lovingly-preserved 40+ year-old LP!. I'm still baffled that Bang & Olufsen didn't think it wise to inhibit 'Sled return to Start' before 'Needle lift' is confirmed by a little switch somewhere.
- I will try demagnetizing at a higher voltage, given that the solenoid does need about 30V to initially pull in.
- I will also look further into providing that (needle & vinyl-protecting) 'Sled return inhibit' function, which will solve the problem permanently.... if slow things down a little...
Progress on the 'safety switch'.
When R92 (see portion of schematic) is pulled high, the sled motor moves (relatively) quickly back to the start position.
I cut the PCB track before R92 (see photo - PCB just to the left of the control switches) and soldered a switch in place instead. When this was closed everything works as usual. When the switch is open, everything works as usual EXCEPT at the end of the LP side the sled doesn't start moving back to the start position until this switch is closed again.
I then fitted a leaf switch so that the leaf contacts close when the arm running up the left side of the solenoid is in the 'Arm Up' position. This arm even has a convenient lug sticking down on the side, allowing me initially to just cable-tie my leaf switch to the wire bundle next to the solenoid: The leaf switch needs very little force to close the contacts. I ran the wires to the main PCB alongside the existing bundle.
At the moment this works. The sled won't start moving until the solenoid releases. Since my engineering is somewhat basic (cable ties, heat shrink etc.) I will see if this works for a while before releasing any photographs of the switch fitting(!).