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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi,
does anyone have any experience and/or reference literature for repairing a Beogram 3500 tonearm that isn't tracking properly? On a disc with widely spaced tracks there is no problem. But discs with more playing time, and the tracks are closer together, the arm is not tracking properly and is sticking.
all conributions will be an increase on my knowledge of the traching mechanism.
many thanks to all
Alan
It seems as though you may have a problem with the pick-up?The stylus suspension becomes stiff with age and less compliant than it needs to be.
Can you try another pick-up?Is the tracking weight correct?Are the chassis transit screw's fully released?
The pick up follows the groove across the record,and as it tracks,it operates an optical sensor which triggers the carriage servo motor to drive the arm inwards,and keeping the pu arm roughly in paralell with the indicator arm next to it.You should be able to see this in action as it triggers approximately once every revolution of the record.
If the pu arm is being drawn way out of parallel,you may have a problem with the optical sensor system,but it may only need adjustment.
Nick
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Thank you for the response to my request. I have been through a whole process of suspicions before I arrived at the tracking possibility. It all started when I bought a reconditioned cartridge from FJS in Germany, and I found that there was a problem with the sound on one channel – my first reaction was that the cartridge was faulty, but after speaking to a few people I realized that it could be due to other things, e.g the tracking of the tonearm. I cleaned the slider bar for the tonearm and regreased it, and found that I had sound on 2 channels( although the sound wasn’t perfect). When I tried playing a few records I found that some of them played all the way through and some had a problem with the tonearm sticking. It seemed that the longer the playing time( and therefore the less the spacing between tracks) the tonearm was prone to sticking. It seems I need to adjust the optical system, but until a week ago I didn’t even know how the tracking system worked. So I need some advice on how to go about checking the tracking and how to adjust it. I have seen that when the stylus sticks, the pıckup arm is not tracking.
As for all the other points you mention – yes, I have checked all of the obvious things.
It seems I need a special test record to set up the tracking properly, but I don’t possess such a thing, nor is it possible to obtain one, as far as I know. If you can indicate how I can set the tracking without the disc, my immediate problem will be solved I think.
Many thanks once again
I strongly suspect the optical switching system - I have tried the diaphragm adjustment, but made no improvement. On certain records(all new ones) it appears as thought the tracking motor is not switching on at all, on other records there is no problem. Could it be that the optical switch is dirty and just needs cleaning? Or do I need to try and find a replacement tonearm?
You need to try another pick-up!!!
In my experience,this machine is very reliable,and what you describe,has all the symptoms of a faulty p.u.
Can you return it ?
yes I can - I bought it from FJS in Germany, and he has accepted to take it back and check it out. Tomorrow I will mail it back to him.
Thank you very much for your help
Could be the servo motor bearings in need of cleaning and lubrication.They tend to bind as their oil dries.
To diagnose it, put a voltmeter across the servo motor and watch the voltage while playing.
Martin
aldo: I strongly suspect the optical switching system - I have tried the diaphragm adjustment, but made no improvement. On certain records(all new ones) it appears as thought the tracking motor is not switching on at all, on other records there is no problem. Could it be that the optical switch is dirty and just needs cleaning? Or do I need to try and find a replacement tonearm?
Beogram 3500 does not use optical system to my knowledge. In the tonearm assembly, there is a switch that is triggered by the angle of the tonearm, and then engages the motor for moving the tonearm assembly.
Someone correct me if I am wrong, but I have been through a lot of these identical 35/45/65/7000 Beograms, and they all use the same tonearm assembly.
/Jacob
Dillen: Could be the servo motor bearings in need of cleaning and lubrication.They tend to bind as their oil dries. To diagnose it, put a voltmeter across the servo motor and watch the voltage while playing. Martin
Could it also be a bad belt for the tracking motor ? If it slips, the cariage would not move as intended ?
Belt is possible.
Tracking is optical.
martin
Bad felt clutch is also possible.
really grateful for all of the suggestions I have received.
I have had separate contact with Martin, and I will be purchasing new belts in the near future. As far as I can determine, the servo belt is not slipping but difficult to be certain. The strange fact is that some records play all the way throug without problem, and others cause tracking problems. These records never play through correctly. and the sticking seems to be in exactly the same position each time(same track). These are actually new records, never been played before, and I have examined them for scratches but found nothing - so why do they stick in the same place? It can't be the slider bar, or it would happen on every record.
My feeling is that it is the optical switch that's causing the problem. I have checked the setting of the diaphragm( as per the service manual), but without resolving the problem. Maybe it just needs cleaning( possible, after 28 years), but I can't see a way of accessing the optics.
I have also sent the cartridge back to the supplier for checking, so I can't do anything more until the new belts arrive and the cartridge is returned. If the problem still exists, I'll come back to the forum.
In the meantime, if anyone has any suggestions for cleaning the optical switch........
many thanks to you all
according to B&O service manual, it is optical, and this is confirmed by the circuit diagram and by the parts list. Thats all I know, I'm not speaking from years of experience. But it seems to me that my turntable looks exactly like the one in the manual.
I don't understand the reference to a felt clutch - where is that?
my turntable is Beogram 3500, 5976
aldo: according to B&O service manual, it is optical, and this is confirmed by the circuit diagram and by the parts list. Thats all I know, I'm not speaking from years of experience. But it seems to me that my turntable looks exactly like the one in the manual. I don't understand the reference to a felt clutch - where is that?
I stand corrected :)
It is indeed optical… I mixed the optical record detection in older Beograms with the tracking optics in the newer :)
/Weebyx
thanks Weebyx. ı don't suppose you know the mechanism of the optical tracking switch, by any chance? My problem seems very strange, in that the tonearm only skips on certain records, and these are largely brand new ones that I played for the first time. Other records play all the way through without problem - I just cannot understand why. The new records are not scratched at all, but the arm just refuses to track - the optical switch is not switching.
aldo: thanks Weebyx. ı don't suppose you know the mechanism of the optical tracking switch, by any chance? My problem seems very strange, in that the tonearm only skips on certain records, and these are largely brand new ones that I played for the first time. Other records play all the way through without problem - I just cannot understand why. The new records are not scratched at all, but the arm just refuses to track - the optical switch is not switching. Alan
My dime is on a bad pickup. As other said, and all the Beograms I have fixed, none has had problems with the tracking besides bad pickups.
I have seen some of the newer repaired pickups from FJS, and they do not look at all like the MMC2 I had refurbished long time ago. I don't know if he has switched supplier or what happened, but I would bed quite a lot that a perfect working pickup will give you a perfect working Beogram.
Before doing anything else, try to see if you can loan or try a faulty record of yours on another Beogram, and if that works try that pickup on yours. That is the only way to find out which part is faulty.
Weebyx,
others have given me similar advice, so I would have been stupid to ignore it. I sent the cartridge back to FJS, and he told me yesterday that the magnet has come adrift, that he will repair it at no charge and refund my postage costs. I'm hoping that the problem will be resolved when I get it back. I would have tried your last suggestion, but I live in Turkey where B&O vintage equipment is almost completely unknown - no second hand parts or knowledgable repairers!
I will inforn everyone who has taken the trouble to help me when I get a result.
many thanks and best regards