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
Dear Enthusiasts,
I have recently acquired a Beogram 3000 tangiental turntable & was wondering if anyone could give me some advice to help get the unit back to its original working order.
The turntable operates correctly, i.e. the carrier travels & then lowers the needle correctly onto the record, however as the record play progresses, the needle arm moves sideways (on its sprung mounting) to a point where it is no longer parallel to the indicator arm, but the carrier does not move & hence the needle reaches the limit of its sideways movement it then 'skips' back to a position where it is again parallel with the indicator arm.
The carrier will move to the full extent of its travel when using the 'lift' buttons & will return to it's 'park' position when record play is stopped.
I understand the turntable was operating correctly before it was stored unused for several years. TBH it's a little on the dirty side & I was wondering if there were any components that would simply need cleaning?
Any advice or opinions would be greatly appreciated.
Kind Regards
Julian
Suspect either the bulb or the light dependent resistor in the rear of the tone arm.
Regards Graham
These decks all work by a detector light sensitive cell being exposed to a light causing the motor to move the arm which stops the light shining on the cell. Clearly one fault can be that the bulb needs replacing!
Peter
Thank you Gentlemen,
I operated the turntable with the covers removed & I noticed a small bulb in the carriage that illuminates only when the needle is in contact with the record. As the bulb is clearly working, could it be that the sensor needs cleaning and/or replacing?
Between the bulb and the sensor, a piece like a paddle will let light to the sensor, when the tonearm is moving toward the middle of the record, when light comes to the sensor, the carriage motor is activated and moves the carriage until no light comes to the sensor, if the paddle is there check for correct adjustment.
And yes clean the sensor with mineral spirit on a cotton swab.
Collecting Vintage B&O is not a hobby, its a lifestyle.
The LDR's do deteriorate to the point where they no longer work.
I have needed to replace several but not recently. Maybe B&O had a bad batch at the time.
I cannot recall where I sourced new stock as it is several years ago.
I have also fitted good used examples gleaned from scrap decks.
Gentlemen,
Thank you again, after receiving your help I have investigated further. You are all quite correct! I have identified the small circuit board on which the bulb & the sensor are mounted. The bulb illuminates, altho it's not particularly bright. I tried carefully 'shorting' across the sensor terminals & hey presto! the carriage started to move. I then experimented further by removing the circuitboard from its plastic housing & shone a small torch directly onto the sensor & this also caused the carriage to move. The torch I used is much brighter than the bulb.
However, when I place the sensor back in the housing it does not respond to the torch or the bulb. On closer inspection it appears that only the centre section of the sensor is exposed to the light through a small aperture in the housing. I notice there is a small lense to focus the light not the sensor.
It would appear to that only part of the sensor will react to light, just a small area that is normally covered by the housing. As such I guess the sensor has 'partially failed' & need replacing.
Would any of these be suitable? http://www.maplin.co.uk/productsearch?criteria=Light+Dependent+Resistors+
I can't find my excess stock but it was several years ago.
The spec in the service manual says 28K so I suggest you try N56AY
Thank you, I've ordered one. I'll report back once I've fitted it.
This is the first time I've worked on a turntable & I have to say what a fantastic piece of design work it is,...... very very clever indeed!
I'm also very grateful and appreciative of the forum members who have taken the time to share their knowledge.
It's not working yet!!!
"yet" is the keyword...
even if it doesn't work, I've had a great time trying!
Regards,
JulianJ: "yet" is the keyword... even if it doesn't work, I've had a great time trying! Regards, Julian
Blame it on Maplin, these LDRs are so small they should be able to send them by E-mail
I located and carefully removed the circuit board that contains the bulb and the LDR. The new LDR from Maplin is almost identical in size & I soldered it in place, making sure it sits nicely in the plastic housing once the circuit board is back in place.
On the first test, it was quickly apparent the new resistor is far too sensitive. The arm almost immediately travelled at full speed even with the 'paddle' adjusted for maximum cover. I got over this by experimenting with different sized 'curtains' made out of masking tape that partially cover the small window, so the LDR doesn't 'see' quite so much light.
Hey presto! I've now got it working to a point that the speed that the carriage travels relative to the lateral movement of the stylus arm looks about right. The circuit is so sensitive that it only works correctly when the cover is placed back on the housing, even the ambient light on my bench will trigger the LDR.
I'm waiting for my stylus to come back from Axel in Germany before I can properly road test the turntable. Fingers crossed!
I'd like to share the 'happy ending' to my first turntable repair! I've received the newly repaired needle from Axel in Germany & am pleased to report the turntable works perfectly!
The linear tracking works beautifully, and incredibly smoothly. All for the sake of replacing a component that cost only a couple of pounds!
I would also like to compliment the sound quality from the 'new' MMC cartridge, I opted for Axels rebuilt Shibata diamond stylus and aluminum cantilever. the sound quality really is fantastic, with wonderful clarity.
Thank you again to those who took the time to share their knowledge, another B&O turntable has been saved !
Regards