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
Hi guys,
I recently inherited two Beogram 4002 turntables with five additional brand new EN20 cartridges. Seeing that I love my B&O collection I decided to restore them as both were defective. The first Beogram actually was a succes on the first go; it was basically a transistor burnout, some failing caps and two resistors failing. It needs some alignment but I wanted to do this when the second one was done. Easier to do two alignments at the same time.
That second one is proving to be more of a problem. It had three of the metal can transistors burned in such a way that i had to restore the tracks. I recapped the entire unit. I replaced most of the old 1w resistors that weren't in spec anymore, the other 2 seem OK. I did not touch any of the existing film capacitors. Now the machine at least doing 'something' besides being dead. I changed the belts using Dillen's replica's.
When I power this machine on, either nothing happens or the carriage will start. If it starts it will move over the platter and then return to the base. Sometimes I can press the start button and it will actually work. Most of the time nothing happens. So.
- Startup isn't working as it should (it starts by itself sometimes)- Start button doesn't work; nothing happens (besides very intermittently see #1)- 33rpm button: when depressed runs the motor but stops when released- 45rpm button: nothing happens- When the tonearm is working it starts at 20% of the record instead of the start. - When it does start it produces good sound at the correct speed- The lamps all seem to be working (sensor, tonearm, selector etc). Perhaps not at the right intensity?
As far as I can tell from my other Beogram, the expected behaviour is that, when plugged in, nothing happens. When you press the start key it will scan the record once, then return. Then you can press start again and it will actually start playing.
I have read through dozens of posts on this brilliant forum and it strikes me that these problems have all been encountered multiple times in one way or another. But because there are so many posts on these subjects what i'm hindered by is that same multitude of posts.
Who can set me off in the right direction? Which problem (or interconnected problems) should I tackle first? This machine can be daunting at first. I don't want to introduce more problems of course.
Many thanks for your help and guidance! Hope to restore this second one in pristine condition as well ;-).
Regards,
Bert
Hi Bert,
when you press the 33 button the platter keeps spinning as long as you keep the button pressed. - it is the record-cleaning function.
doing the same with 45 isn't doing anything at that stage, it only switches the speed to 45 after start has been activated if so desired.
check the contacts under the keyboard to make sure they are clean and not touching anything they shouldn't without pressing the asigned button.
have you checked the positioning ruler ? If that has shifted the arm lowering point would be wrong.
hope that is helping.
ALF
Ah okay clear, I was under the impression that the 33 button would keep spinning as a manual speed selector. Obviously rtfm for me in this regard ;-).
I have cleaned the keyboard and the contacts using emory paper and Deoxit D5. So they are clean and making good contact when pressed. Nevertheless the start button never seems to do anything, it only does something when the turntable is powered on and starts moving on it's own (first pass).
Let me check the ruler, as far as I can see that is in the correct position. My first guess would be that some sensor is off base / out of alignment. But I am most certainly not an expert on this turntable's exotic design. Could just as well be something on the main PCB or, horror, the relay or one of the IC's.
I checked, everything is in place as I think it should be. The same as the other 5521 Beogram.
I've tried to find the service manual for this type but couldn't find it. Is there another one from another type that is compatible?
Thanks,
Hi,
Firstly, pressing the 33 RPM button works as it should. It's for cleaning records and will only spin as long as the button is pressed.
Secondly, the other deck is not supposed to scan the record first before you can play it. I suggest you take a look at the mechanical adjustments of the arm distance to the platter. It should be 23 mm measured from the top of the arm with the bulb to the platter. Only then will the optical sensor be able to see correctly if there is a 12" or 7" record on the platter.
Filip: I suggest you take a look at the mechanical adjustments of the arm distance to the platter. It should be 23 mm measured from the top of the arm with the bulb to the platter. Only then will the optical sensor be able to see correctly if there is a 12" or 7" record on the platter.
I suggest you take a look at the mechanical adjustments of the arm distance to the platter. It should be 23 mm measured from the top of the arm with the bulb to the platter. Only then will the optical sensor be able to see correctly if there is a 12" or 7" record on the platter.
I don't believe that is quite how it works.The 23mm distance is to set the height of the fixed arm which in turn is used to set the position of the tonearm. That properly sets up the angle at which the Beogram phono cartridge stylus will meet a vinyl record. The fixed arm detector lamp and sensor detect the pulses of an empty platter and determine if it is okay for the tonearm to lower. That sensor lamp and and voltage signal should be checked using an oscilloscope to make sure it is well within proper operating range.
The set down position from start is determined by the tangential position sensor and scale along with two switches (ES - end stop and SO - switch off). There are tab actuators on the sliding tangential arm transport that engage the two switches. There is another photo sensor and lamp that read the pulses coming off the position scale that determine position for set down and the run-off groove. That sensor is another item that should be measured to make sure it is properly within operating range.
The tangential arm transport and sensor scale have position adjustment screws to fine tune where they need to sit for the Beogram to operate correctly.There are quite a few other adjustments to check. They are listed in the Beogram service manual. I suggest familiarizing with those if you plan on maintaining your Beogram yourself.
-sonavor
Regarding the service manual...Your Beogram 4002 Type 5521 should be very similar to the Type 5523. It you can't find those you can look at the Type 5513 as it is very similar.
If your run into something you can't find the answer to then post some photos and someone here on the Beoworld Forum should be able to answer it.
I have indeed now read the 5523 service manual. Based on the manual and some experience I changed:
- All old 1 W resistors + old ½ resistors- I changed all the basic motor transistors surrounding the burned out ones. They still tested good but HFE was way off- In the PLAY circuit I changed the base diodes running into the power supply- I changed all the old Philips film capacitors; some were breaking
Now the PLAY function works! Yeah!
I had already lubricated everything and it is smooth now.
One final problem remains, which is that the start position (start lowering onto the record) is incorrect. Instead of starting at the start groove, it will start roughly 15% inwards.
I suspect this is an alignment issue, but which one?
Hey there,
damn I was really convinced that the 'scan once, play second' was the expected behaviour ;-).
Now that I have repaired the other machine your remark makes sense as it doesn't have this behaviour. But the second previously broken deck is not playing at the start position (start groove) but starts at roughly 15% inwards.
My guts tell me this is probably an alignment issue but I can't remember where to start.
Did you check the Photo darlington adjustment on page 4-2 of the service manual. That sets the voltage on the 4IC1 collector to 5V. Perhaps that is out of adjustment and causing a problem in the detection of the set down position.
Also, you want to adjust the position scale so that it is very close to the slit where the sensor is. If it is too far away then the sensor may not detect properly. -sonavor
Hmmm. I double checked but I can't find any issues with it. Voltage seems to be OK.
I understand the repositioning of the position marker, but isn't it true that playing with this will only give me roughly 0.7cm of play? That is not enough as the drop point is about 2.4cm inwards.
Of course I will check again, little bit hesitant to changing this as it's easy to mess up alignment. Don't want to introduce more issues. Dicking around with mechanical parts is often a sure way to create a mess.
The position marker was at the complete left, I moved it to the middle and the complete right. Neither change has an bearing on the lowering mechanism. It still lowers roughly 15% too far into the record.
Is this not indicative of a failing lamp in the sensor? Perhaps the brightness is off because of the age of the lamp? Just thinking aloud here, this thing is way over-designed technically so the actually issue can be a silly as an old lamp........
I have read and reread the service manual but can't find a clue as to any alignment of the tracking system or circuit. I think this is odd. I can't help but imagine that the issue (15% off from the start groove) is something that must have happened to people before. I also can't shake the feeling that it has got something to do with the lamps.
I found the beolover article (https://beolover.blogspot.com/2018/01/beogram-4002-5513-restoration-of-arm-lowering-and-tracking.html) which describes a change on the basic system. It seems that the light intensity is rather vital. In my mind it would thus be reasonable that, if something is off with my system in this regard the tracking would also be off.
But I am really hesitant to just muck around. This turntable is over-designed to a point where just randomly doing stuff can and will result in even more problems.
Can anyone give me pointers on this problem?
notwist: The position marker was at the complete left, I moved it to the middle and the complete right. Neither change has an bearing on the lowering mechanism. It still lowers roughly 15% too far into the record. Is this not indicative of a failing lamp in the sensor? Perhaps the brightness is off because of the age of the lamp? Just thinking aloud here, this thing is way over-designed technically so the actually issue can be a silly as an old lamp........
That is what I was referring to. It sounds like you tried repositioning the scale left and right which is fine to try but you did not adjust it in and out to be closer to the sensor. The lamp can be suspect if it is still original but that can be compensated up to a point by the service manual adjustment using trimmer 1R88. I showed the adjustment here. I had a Beogram 4002 one time that was not detecting the run-off signal generated by the position sensor. I monitored the signal with a scope and saw there was no signal until I re-positioned the scale closer to the sensor. I am not saying that is your problem for sure but if adjusting the scale left or right doesn't fix the problem then the issue has to be with the sensor and when it does detect the black marks on the scale. It sounds as if your Beogram is not registering the first set down mark on the scale. Can you post a photo of your scale? Are the black markings all there and correct? This old post I made shows a couple of good photos of the Beogram 4002 position scale.
You say your set down point is about 15% off. The set down point for a normal record is the 30cm mark on the scale. It appears your Beogram is not detecting that mark (is it missing or worn?). Instead your Beogram detects the 25cm mark which is 15% in.
OK clear, thank you very much! I am so happy with these pointers, the exotic layout of the turntable makes it too easy to mess things up.
I will check this in the lab next thing tomorrow. It's very late now, too many projects and too little time. By my knowledge the ruler looks OK, but I will check that as well.
Thanks!
If your position scale looks good, which I would expect it to, then the issue is with the sensor. That first bar for the 30cm position is thinner than the next bar.Have you tried a 7 inch single record? If not then I would suspect it wouldn't get detected either. I wouldn't be surprised if the run-out groove detection was failing as well. What is the voltage on the collector of 4IC1 when the black mark is over the sensor and what is the voltage when the clear part is over the sensor?-sonavor
One other thing to check. Did you replace the 1uF electrolytic capacitor 1C33 ? If not then you should do so. I always replace all of the old electrolytic and tantalum capacitors if they are still the original ones.
Hi Sonavor,
This is not my first hassle with B&O and European made equipment. So as a precaution I updated all capacitors including several of the film capacitors known to be rather shoddy quality. This includes the tantalums. Exchanged with mostly film and mlcc and the larger reservoirs with electrolytics (vishay).
I made two photos of the bar, in my opinion this is OK. No scratches but perhaps I'm missing something here. On first glance it seems the same as the one on my other Beogram 4002. Which suddenly works 100% and doesn't do the 'scan once' misschief anymore. But based on my experience with this one I would do a revision on that one as well. But first the problematic one.
The black sensor has roughly 2mm of space between it and the ruler (scale). It would be difficult to minimise that gap and it seems to be roughly the same on my other Beo 4002.
it is too busy here, need to put out fires all the time. So what I did in the meantime is to exchange the revised main PCB with the untouched PCB in the working Beogram.
The result is: the revised PCB works in that Beogram. The carriage moves to the correct lowering point and plays well.
So, it seems that the problem is not originating from the main PCB. At least not as far as I can see from the circuit. If it were down to an issue on that PCB it would have migrated to the other Beogram. Which it did not.
Question is, now what?
Then it sounds like your issue is narrowed down to the position sensor and lamp. Ideally you would monitor that signal with an oscilloscope to make sure the voltages are in proper operating range and not working with voltages that are at the edge of a limit. But since your second board works in the other Beogram then that puts the sensing problem on the sensor, lamp and position scale. I would still look at how far the position scale bar is from the slit in sensor housing. Try to put it as close as possible without touching each other.
before heading home I positioned the sensor as close to the scales as possible, this had no effect. I don't know if it's at all possible to upload a movie here, that would show you the behaviour (easier than text). I don't have single unfortunately so I can't reliably test that feature with regards to the sensing array.
You are right, measuring voltages would be smart. I don't think I have to hook it up to my oscilloscope for that, this is all rather basic work that can be measured with my workbench multimeter. The question is what voltages are we looking for? Which components are vital to the operation and must operate within a certain bandwidth? And under which circumstances? Is there a way to test the sensor to see if it is malfunctioning? What are the options to replace it (if any).
I don't usually do turntables and this design is somewhat eccentric to say the least. That is why you have deep knowledge and I do not, such knowledge can only come from a load of time spent with this design. For me, even though I am technically skilled, it is essentially a pandora's box with regards to specific features and how they cooperate.
Again, many thanks for your help and advise.
There are of course the sensor setting voltages per the service manual.After that though, you need to see what gets picked up on the main board from that sensor.I usually measure the collector of 1TR17 and the node of 1D41, 1R82, 1C33, 1D42 if checking the performance of the Run-Off stop signal.If none of the functions from the position sensor board were working then I would suspect the wiring between the boards but you are seeing the 25cm position get detected. I would still be interested if the 17cm position will detect.Since the board in question works in your other Beogram 4002 unit though I would have to suspect your position sensor and/or lamp.It isn't producing the necessary stimulus on that narrow 30cm mark on the position scale. It waits until it gets the large marking of the 25cm position.I think you have exhausted all of the possible mechanical parts of the puzzle.
When you try the board from the working Beogram in this Beogram it too fails to detect the 30cm position, correct?
I have indeed transplanted the unrevised board to the revised Beogram and it is exhibiting the same behaviour. Thus I would conclude that the sensor is the culprit and perhaps it's direct surrounding components. The lamps in both machines appear to have about the same brightness (the lamp in the arm).
I will try to get a 17cm (single) from somewhere, if lucky someone can bring it to the lab tomorrow. Will check this out immediately to see if that works.
But the real question in my mind is, if the sensor is broken can it be replaced? Either with a DIY part or another type of sensor. I'm not sure about this at all because I have no clue how to test the sensor in an objective method. Shouldn't these give an ohms reading?
I have removed the housing to get a better look at the components in question. It appears to be an infrared diode and a photosensitive diode. Not entirely sure because the service manual I am using is showing different parts (lamp or led, not infrared). Perhaps I am wrong about the IR.
In the end this setup (a light source and a light 'gatherer') is really common. So the question is what components can we use to replace the old ones. If necessary of course. I can desolder them and double check some parameters.
Maybe i'm going about this the wrong way, if so then please excuse my inexperience with this machine. I fully understand that in respects to the precise workings I am way out of my league. Then again I restore and repair much more complex machinery so perhaps this is why I am simply trying to exchange the parts where the fault appears to be coming from.
I will check the power supply rails once again as wel. If the light source doesn't get enough juice it will likely produce a weak light (or IR) to bounce off from.
I have yet to run into a case where the sensor was bad although it seems a possibility. Maybe Martin (Dillen here on the forum) can answer that.I always change the light source. I have been using a Cree C503B-AAN-CY0B0251 for my replacements. They have given me good results so far. After the installation I check and adjust 1R88 to set the proper voltage then check the signals that result from that sensor.
your article is quite clear, thank you very much. The light source that is in this machine gives out very little in the way of light at the moment. Not near the level of brightness as in your article. So let me order this replacement and we'll try it out with the alignment adjustments. It will take a day for the lamps to get to the lab so I will report back on Thursday.
I believe that we should have a compatible sensor in 'the pantry' as well, let me check inventory.
Again, many thanks for the help. It is too nice of a turntable to just let it be spare parts.
Kind regards,
notwist: It is too nice of a turntable to just let it be spare parts. Kind regards, Bert
It is too nice of a turntable to just let it be spare parts.
That is for certain. I can say from my experience that these Beogram 400x turntables are very rugged. The only thing that would prevent getting one back running properly again would be some extraordinary event like someone taking a sledgehammer to one. Probably a little over dramatic there but the point is that none of the parts in the Beogram 4002 are parts that cannot be be repaired or sourced.-sonavor
so the replacement LED arrived in the lab. I replaced the LED / IR that was in the machine. With the new LED (as per your part number) in there, the whole system is going completely haywire.
When I power up, there is light. The motor starts spinning on itself, 33/3 rpm is lit up. Pushing automatic just moves the tonearm over the record completely. If I stop it will return to it's 'off' position but the motor won't stop. Just keeps spinning as if it wants to move even further back.
I think that my machine is not using a regular LED. When I test the component I desoldered, it measures much different (even though it registers as a diode) then the new one. I think that my machine is using an IR diode which explains why there was no light to speak of.
Of course I can measure voltages again on the LED (it's about 2.1v) which is also quite a load higher than your post (which has it as 0.7v). My schema says it should be about 1.1v so it's already way too high. I can check to see if I can get it to back down using the trimmer. In my schema 4IC1 is determined as 'srd 212' which I can't find anything on. However, 4D1 is registered as OP160 which is a infrared emitting diode, unobtanium unfortunately,
It seems an incompatibility has arisen. Otherwise I am a bit stumped.
replacing the new LED with the old IR diode (tested, working) does not change the haywire behaviour. Essentially it seems that it is now really out of whack.
Tried what happened when I press 'start' with all components back in there. The arm moves across the platter (record on, spinning by hand) and then returns to the start position. It does not lower anywhere. When in the start position, the motor of the assembly does not stop, keeps running. The motor for the platter also keeps running. Also the 33 rpm is still lit.
Basically it seems that it is now immediately starting in manual mode? Or something like this? Why? I only desoldered that one LED and touched no other components. Did I overload the sensor thereby breaking it? Would this whack the machine in such a manner?
Voltage on the LED / IR is down from 1.9v (LED) to 1.1v (IR). Seems to be OK. I can still change that voltage using the trimmer, not that it helps in this situation.
I find this completely odd.
The Beogram not turning off means the catch on the sliding scale is not engaging the first microswitch on the assembly. That is the SO switch. Either that or the SO switch is not working.
With the position sensor lamp replaced you need to measure and adjust 1R88 so there is 5V on the cathode of the sensor when the light is shining through a clear part of the sliding scale.
That sets the level. With a troublesome position sensor I often remove the platter and observe the operation of the position scale. You should be able to see it engage/disengage the two microswitches (SO and ES). It they are not being engaged properly then the scale assembly needs to be repositioned.When the platter is removed, pressing Start should always result in the Beogram setting down at the 30cm position as the fixed arm detector will not be getting any pulses from the empty platter.
Another thing to check is the voltage coming out of the sensor and what shows up on the base of 1TR17 when the position scale is on the clear part of the scale and when it is blocked by a black position mark. It might require adjusting/bending the LED light source to aim at the slit in the sensor housing properly. Those are all the components involved with the arm position detection. Assuming your Beogram power supply voltages are all good then your problem has to be with those position detection components (sensor lamp, sensor, ES switch, SO switch, sliding scale mounting position, 1TR17). That's why you need to check the cathode voltage of the sensor and then see how it is controlling 1TR17. The 1TR17 transistor is what initiates the command from the sensor to drop the tonearm. The ES microswitch physically signals the Beogram to return to stop. The SO microswitch turns power off the control circuit.
To clarify checking the voltage of the position sensor here is what the service manual is calling for.
Ok let me check this step by step. I have positioned the light source (both LED and IR) using a micro ruler; it is aligned properly at the slit. The IR beam is quite wide so it will target the entire slit. I will try doing this with the housing off and a makeshift darkening panel. See if that changes anything.
What is bothering me is that on 'power on' the platter motor immediately engages and it never stops. Not even on stop. I am also unsure why this happened as I am a skilled technician with good solder skills, nothing out of the ordinary happened. As my experience is in other types of machinery, I would not think that a mere microswitch causes this aberrant behaviour.
The immediate start is also happening without the scale bar, so it happens with and without that positioning scale. Power on = motor starts, 33rpm it lit and nothing else happens.
Nevertheless, I will of course follow your steps and report back!
Correct, power to the motors is managed by the SO switch. There has to be a physical presence to close that switch. Otherwise the Beogram would have to have something holding the switch closed to allow the motors to run.
If you have the positioning scale removed you can push on the switch with your finger and verify that it shuts the motors off.-sonavor
I am including the service manual procedure here -
I was able to rearrange the scales slider in such a way that the SO switch clicked. It is now not starting automatically, it seems a slight skewing of the slider was enough that the switch did not get enough pressure. Now on startup all is silent (as it should). Both ES and SO switches appear to work, I can start the trolley and the trolley moves back to the initial position on stop.
Then I tested the voltages on the phototransistor. As per SM I directed the tonearm to the mid section of the platter on a transparent section. On that section I am only getting 0.94 volts. On a black section I am getting between 9.22 and 10.4 volts. These readings seem to be way off. This is with the tone arm up.
Interesting. Let me check that transistor now.
I did another test and strangely enough something changed. Whereas before it would land roughly 15% off on the record (inwards), now it starts almost correctly. I would say that just 2 or 3 millimeters to the right and it would lower into the start groove. Now it starts when the audio is already, still not in the start groove. Optimal would be 5mm to the right, max would be 7mm to the right (start of the start groove).
I have made a video to show the behaviour:
https://youtu.be/5GP8Rbp-0G0
I hope this is clear enough. It almost seems as if some calibration is needed on the tone arm or assembly? And is it my imagination or is the arm assembly not moving 100% correctly? It is as if is understands it needs to stop and lower the tonearm, but then decides to go a bit further. I can hear that the assembly wants to stop but afterwards it appears to 'slide' some more. I hope i'm making any sense here.
All belts are new and ordered from Beolover.
That is good progress.So what happened is your light source is finally aligned where it is activating the sensor better. The first black marking at 30cm is being detected and initiates the tonearm lowering.I would still re-check the service manual adjustment for the light source (using 1R88). You should be able to get 5V for the clear part of the scale. 10V to 11V for the black markings sounds right.It appears that now you need to address your tangential tracking sensor. That is the one at the base of the tone arm.Take the top and lower platters off and run the Beogram that way. You should see the tonearm lower at the 30cm mark and the arm should just sit there, lowered in space.If it starts moving on its own then that is because the tracking sensor is not adjusted correctly and it thinks it needs to drive the arm forward. The service manual describes that adjustment and we have a number of posts on the Beolover Blog that show that adjustment.In the link that I included there are quite a lot of adjustments to check and make on a Beogram 400x. I have seen many a Beogram 400x turntable where they will play a record and appear to be functional but things are actually out of adjustment and the Beogram is not actually working at its optimal settings. These turntables are really great audio components and you want to have them working at their full capability.
Okay let me read through that post, lot's of things to consider.
I have tried setting the voltage again using the trimmer. Unfortunately on a transparant section the highest I can get is roughly 1.1 volts. Nowhere near the 5v you are mentioning. That is the highest setting on the trimmer, it doesn't give much in the way of leverage, perhaps 0.3 volts either way. Maybe the trimmer is broken, I can desolder it and test it on the bench. Replacements are at hand.
It could also be that my version of the Beogram which uses the infrared method has a different voltage setting. You see, 0.9v versus 5v is, in my opinion, way too much leeway. Perhaps on my version it is supposed to be a lower voltage, but I will check the trimmer and associated transistor nevertheless.
Let me report back after I have done my reading job ;-).
The Beogram 4002 service manual hasn't changed regarding the types that have the position scale and light sensor. That adjustment procedure is the same even for the Beogram 4004.
Can you post a couple of photos of your measurement points? Where are you connecting your DMM ground and positive probes?I dug up a couple more photos of my position sensor adjustment measurements.I probably confused things a bit as some of my posts I show adjusting/checking 1R88 by measuring at the base of transistor 1TR17. On those I want to make sure 1TR17's base is at 0.7V when a clear part of the position scale is in front of the sensor. That is of course a different way than the service manual.In these two photos I am checking per the service manual at 4IC1's collector.I used an oscilloscope for this particular check as I wanted to observe the signal on the different scale positions.
This first photo shows where I put my probes -
This photo shows the signal (my comment in the photo referencing the measurement at 4C1 should have said 4IC1) -
When you are checking the position sensor at 1TR17, here is a photo of that measurement.For that measurement you are looking for the measurement to be around 0.7V when the clear part of the position scale is in front of the sensor.
Make sure you aren't confusing the two measurement points (1TR17 base and 4IC1 collector).