LP12 Radikal problem
Posted: 2018-04-16 20:23
Everyone who has a Radikal motor on their LP12 and either a Trampolin or a Urika needs to read this. If your retailer does the service, specifically ask him about this issue! If you service it yourself, check this!
The Radikal motor is housed in a big can, which is very deep. Below the can is the left rear trampolin foot and the distance between these two is very small. On some LP12's (currently 2 out of 4 that I have checked), the can actually rests on the foot. This causes the LP12's musical performance to drop significantly. Bass gets sluggish and untimed, music becomes a bit "seasick" instead of rock steady. The following picture was taken with a GoPro camera by Erik: What you see in the picture above is
To the left: Part of the left suspension spring,
Upper middle and right: Keel subchassis,
In the middle: Radikal motor can with its aluminium lid at the bottom,
Below the can and its bottom lid, on the left side: The rear left Trampolin foot assembly.
If you have Radikal and Trampolin, there is also a screw on the Trampolin foot that protrudes right below the can. Unless this screw has been grinded down in length, it's guaranteed to press against the motor can. On the Urika, the feet are rotated 45 degrees to move this screw away from the Radikal can.
One way to test if the can touches the foot is to make a long piece of thin paper that gets more narrow on one side and protrudes through the hole below the arm pillar (picture by Paolo below). Place it on the Trampolin/Urika, install it below the LP12 with a few screws and then place the LP12 on a table, standing on its Trampolin feet. Now pull on the piece of paper to the right of the arm. Is it stuck? Then you have a problem. If you have the problem, your Trampolin/Urika needs to be moved down, away from the can. I have grinded down the outer perimeter of the Trampolin foot slightly and thought that was enough, but when I did the paper test, it turned out it wasn't - the can and foot were touching. So I have added some wooden strips between the plinth and the Trampolin, which I bought from a hobby store. They had lots of varieties there, so I bought two of every kind. What's needed is a width of 8-10 mm and a thickness of 1-2 mm. On most LP12's I suspect 1 mm will be enough, but there are no such thin strips in my newly acquired collection. With 2 mm, you might begin to get problems with the screws not gripping as well in the holes of the plinth (in which case you can use a longer screw). While I'm sure that different types of wood are likely to sound a bit different, the ones I have which are most uniform in thickness are 8x1.5 mm strips of Lime-tree. They're quite light and soft, so I have removed the old felt strips (the purpose of which I believe is to prevent rattling). I wanted to try Balsa as well, but they varied so much in thickness; 1.2 to 1.6 mm. I don't really know what is optimal, perhaps we can help eachother find out what is?
Wood type?
Thickness?
Original felt strips - in place or removed?
Please note that all plinths are a bit different, so you will need to verify the dimensions on yours. I have a Linn original in maple and used the following measurements when cutting and drilling my four pieces of strips. These strips are for my Trampolin. The front and rear strips are 410 mm long and the left and right are 305 mm. Please note that when drilling, the strip easily cracks. If you clamp it between two other pieces of wood, you can prevent this. Or you might make it by being very slow and gentle. It's good to have more strips than you need, in case you break them. EDIT: I see now that I forgot to draw the hole in the middle of the rear strip.
I didn't use any glue when installing the Trampolin with the strips lying on each of its four edges. Glue would surely have made it easier, but I felt a bit sceptical of it and the installation is doable anyway. After the installation, the Trampolin sits 1.5 mm lower than before. And the result is a completely transformed musicality of the LP12. Much, much better.
The Radikal motor is housed in a big can, which is very deep. Below the can is the left rear trampolin foot and the distance between these two is very small. On some LP12's (currently 2 out of 4 that I have checked), the can actually rests on the foot. This causes the LP12's musical performance to drop significantly. Bass gets sluggish and untimed, music becomes a bit "seasick" instead of rock steady. The following picture was taken with a GoPro camera by Erik: What you see in the picture above is
To the left: Part of the left suspension spring,
Upper middle and right: Keel subchassis,
In the middle: Radikal motor can with its aluminium lid at the bottom,
Below the can and its bottom lid, on the left side: The rear left Trampolin foot assembly.
If you have Radikal and Trampolin, there is also a screw on the Trampolin foot that protrudes right below the can. Unless this screw has been grinded down in length, it's guaranteed to press against the motor can. On the Urika, the feet are rotated 45 degrees to move this screw away from the Radikal can.
One way to test if the can touches the foot is to make a long piece of thin paper that gets more narrow on one side and protrudes through the hole below the arm pillar (picture by Paolo below). Place it on the Trampolin/Urika, install it below the LP12 with a few screws and then place the LP12 on a table, standing on its Trampolin feet. Now pull on the piece of paper to the right of the arm. Is it stuck? Then you have a problem. If you have the problem, your Trampolin/Urika needs to be moved down, away from the can. I have grinded down the outer perimeter of the Trampolin foot slightly and thought that was enough, but when I did the paper test, it turned out it wasn't - the can and foot were touching. So I have added some wooden strips between the plinth and the Trampolin, which I bought from a hobby store. They had lots of varieties there, so I bought two of every kind. What's needed is a width of 8-10 mm and a thickness of 1-2 mm. On most LP12's I suspect 1 mm will be enough, but there are no such thin strips in my newly acquired collection. With 2 mm, you might begin to get problems with the screws not gripping as well in the holes of the plinth (in which case you can use a longer screw). While I'm sure that different types of wood are likely to sound a bit different, the ones I have which are most uniform in thickness are 8x1.5 mm strips of Lime-tree. They're quite light and soft, so I have removed the old felt strips (the purpose of which I believe is to prevent rattling). I wanted to try Balsa as well, but they varied so much in thickness; 1.2 to 1.6 mm. I don't really know what is optimal, perhaps we can help eachother find out what is?
Wood type?
Thickness?
Original felt strips - in place or removed?
Please note that all plinths are a bit different, so you will need to verify the dimensions on yours. I have a Linn original in maple and used the following measurements when cutting and drilling my four pieces of strips. These strips are for my Trampolin. The front and rear strips are 410 mm long and the left and right are 305 mm. Please note that when drilling, the strip easily cracks. If you clamp it between two other pieces of wood, you can prevent this. Or you might make it by being very slow and gentle. It's good to have more strips than you need, in case you break them. EDIT: I see now that I forgot to draw the hole in the middle of the rear strip.
I didn't use any glue when installing the Trampolin with the strips lying on each of its four edges. Glue would surely have made it easier, but I felt a bit sceptical of it and the installation is doable anyway. After the installation, the Trampolin sits 1.5 mm lower than before. And the result is a completely transformed musicality of the LP12. Much, much better.