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,
I have an old Bang and Olufsen music system which was originally owned by my Great-Grandparents in the 1970's. It consists of a Beogram 1203 turntable, Beocenter 1600 Amplifier/Center and two Beovox S30 speakers. I recently replaced the old stylus (B&O 15µ Diamond SP14) for another identical one. As it was well used, this became worn and visibly out of shape. I noticed as it was on its last legs, there was no sound in the right-speaker. I thought this would resolve with a new stylus but it's still a problem! I have checked all the connections and it's not a speaker thing as it works in stereo for radio and tapes. I really need some help with this. I'm happy to explain anything else about the system - but I don't want to take it apart myself and use trial and error as I don't want to risk breaking what is both an old family possession and also an extremely good piece of audio equipment from the 70's! I've also spent alot of money replacing parts of it to keep it looking new and functioning properly and I'd like to think it can keep going.
Any help would be much appreciated,
Thanks and regards,
Henning
Seems like a new stylus would be a good investment anyway?
It's possible that the actual pick up,that the stylus fits to,is faulty?The pins become very tarnished with age.The stylus needs to fit on securely for it to work.
The wires in the turntable din connector to the amplifier can break too.
Nick
Thank you very much for the responce. I have had another look at it and the pins on the pick up look brand new. I have double-checked that it fits onto the arm as well and there doesn't seem to be any problem there. I have also had a look at the din connector and the plug looks perfectly fine and goes into the back of the amplifier nicely. Unfortunately, I am still unable to hear through the right speaker unless I switch it to mono. Are you suggesting that the problem may be with the cable rather than the plug? this all looks in good condition as well... Everything was set up in my Great-Grandparents house until it was moved in 1996. Until 2007 it was sat in the spare room and that's when I started using it. All this time it has been well cared for and is in good cosmetic condition.
If you have any other suggestions, I would be most grateful!
Thanks,
You can test if the amplifier is working on both channels on the gram input,by carefully poking a small screwdriver into the gram din socket,and listening for a buzz from each speaker as you touch the connectors.Set the volume low so as not to damage the speakers.If you do get a buzz from each speaker,you can assume the amplifier is ok,and that the pick up or cabling is faulty.
I have put a small paperclip into each of the holes and a buzz can be heard in the left speaker but not in the right. I suppose this means I can stop worrying about problems with the turntable, although do you know where in the amplifier this problem could be? I have noticed that sound does come out of both speakers in Stereo when I listen to the radio, so that must narrow the problem down a bit.
Thanks again,
Henning.
Well, you are down to the switches and the RIAA then. Aren't you ?
Martin
As Martin say's,the problem is definately in the Beocentre.If it's poor switch contacts,the sound will appear from both speakers when you tap the phono button.As there is no sound from one speaker though,it's more likely to be the phono preamp ("RIAA").This boosts the small signal from the pickup to the same(or close?)to that of the other functions.Most likely failure is a capacitor,or at worst,one of the transistors.
Can you solder?The circuit is on site (see Beocentre 1800,the same thing but including turntable)if you care to upgrade your membership(good value!)
The phono preamp is a seperate module,although there are a couple of caps on the main board for phono routing.
I have pushed the phono button and sound comes out of both speakers. Will fixing this still require soldering? I am experienced enough at soldering, although I'll need to buy a new iron as mine isn't working. I also have hard-copies of the B&O's schematic diagrams which came with it, although they're not the easiest things to follow!
Do you mean music comes from both speakers when you push the button,or just noises?The switches will crackle when operated,but if you can restore the actual sound from records by moving the button,it just means the switch contacts are particularly poor contact.You won't need to solder anything in this case,just spray some contact cleaner into the switch.It's fairly accessable once the cabinet top is removed.
When I press the phono the button, a click comes through both speakers, although music only comes through the left speaker. I'm guessing that this means the problem is down to something other than poor contacts. What do you think would be my next best course of action?
Pretty basic, really; Put a scope to the signal path and see where the signal is lost.Most likely somewhere in - or around the RIAA.
You may as well just replace the "usual suspects".These are the little coupling capacitors C200/204 in the rh channel,and C200/204 in the lh.
They may be tantalum bead types,that look like blobs of brown paint with wires.You can use standard caps instead.
The circuit references above assume your unit has the seperate preamp pcb as the Beocentre 1800,which is essentially the same unit but with an integral turntable.