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hi, new to this so bear with me, have the above and just replaced the stylus, but noticed that the wires that run through the arm to the connection block have broken, can anyone tell me if this a special wire and the connecting sequence to the connecting block in the arm to the 5 points at the rear of the arm.
help appreciated
david
Hi David:
An interesting project that I too was presented with when I purchased a BeoGram 6500 turntable off of eBay a while back.
One of the problems is that the wire type that runs through the cartridge arm is very unique, specific and very difficult to work with. In my situation, the plastic cartridge socket had separated (apparently when a previous owner attempted to remove the cartridge) and had been pulled out so hard, that the wires were ripped completely from not only the destination board, but severed at their mid-section. As such, I could not just re-solder them back onto the board and splicing them would be impossible.
My first order of business was to attempt to purchase similar wire from eBay - specifically from a UK based vendor. Upon arriving, I realized immediately that the B&O version was much, much thinner. About as thin or less then the diameter of a human hair (if I remember correctly).
I then realized that I had in my parts collection, a broken arm assembly from a BeoGram RX Radial turntable. Being a radial table, the length of the wires within the tube are much longer then that of the linear tracking tables. This provided me with a supply of the exact wire and of more then adequate length. I simply cut the aluminum tube and harvested the wires.
This is where the fun begins. It turns out that this wire is insulated. And of course, we know that it has to be or it would short against each other and to the aluminum cartridge arm. However, it doesn't look anything like your typical insulated wire. It actually has a very tough, albeit thin, coating that must be removed at all solder points. Those points being at the cartridge socket at one end and the small circuit board at the other.
The most challenging part of this project was to properly strip the tiny wires at their solder points and to tin them for soldering. After experimenting with various solvents, I succeeded in "stripping" the transparent and very tough insulating coating with methylene chloride paint stripper. This is the clear gel stripper that is available here in the US in all of our building centers. Careful, as it will burn your skin.
Applying the MC paint stripper has to be done very carefully as you only want to remove the insulating coating at the very ends of the wires. I did this using my magnifying glasses and a toothpick. I applied it, waited and removed it with a tissue pulling it toward the tip so as to not risk stripping any more of the insulator then necessary. It is a very surgical job, to say the least. I then applied some flux with a toothpick to the exposed tip, tinned it with my iron and hoped for the best. Upon inspecting the end, it worked perfectly. A shiny lead-covered solder-worthy tip was successfully accomplished. Very tiny though; you'll need a magnifier for sure.
That is the most difficult part. Once you get all of the wire successfully tinned on one end, you can start micro-soldering with your smallest solder tip. I did the cartridge socket end first. It doesn't matter which wires go where at this point as you'll test and figure the proper order when soldering to the board end. Once all four wires were soldered and inspected, I epoxied the plastic cartridge socket back onto the aluminum arm.
I then snaked the wire through the arm being very careful to follow the same course as the original wires. Once you have succeeded in running the wires all the way to the board, you can start the whole tinning process over again. But... be very careful not to cut the wire too short and leave a little extra length just in case you make a stripping/tinning mistake. As far as which wires go where, there are two channels with a hot and ground each for a total of four wires.
As far as the proper order for each wire with respect to the board, you will need the service manual which is available to Silver members here on BeoWorld. With the service manual and your ohm meter, you can sort the wires relative to their respective cartridge socket. I used some small tape labels to mark accordingly so as to avoid confusion and mistakes. I actually used a clipped off resistor lead to act as a test pin in each of the cartridge socket points. Once this is done, you can begin to solder the board ends to the board.
This was a very challenging but rewarding project for me and the best part is that I saved a beautiful BeoGram 6500 turntable. This model has the desirable built-in RIAA board.
Good luck and should you have any questions, please feel free to ask.
Micheal, thanks for all the info, its just what i needed... sounds like I'm going to have hours of fun...just need to track down the correct wire .. will let you know how we get on, thanks a million.
Michael, thanks for all the info, just what i needed, had a feeling its wasn't going to be easy, but looking forward to the hours of fun doing it and hours of pleasure once its back up and running will need to track down that special wire, any one with info on that let me know. off to some searching will let you know how we get on