Beogram 3000, type 5228, vinyl deck from 1973

[N Cook]

Time again for someone's heirloom.
Cured the main problem of erratic speed - solidified grease on the main
swing arm , stopping the thin moulded hard rubber?(dark brown colour) edged
pulley, freelyly swinging and engaging with the stepped conical motor bobbin
with the pull in of the main platter drive band.
But there is an intrusive noise associated with this pulley , once a
revolution. Nothing obviously wrong , no cracks, bulges or anything on this
edging - anyone know what it might be from ?
All I can think of is the edging has worn to the point that at one part of
the edge that it is very close to the underlying metal.
I'm thinking of a fudge of trying a wide rubber drive band, stretched over
the edge and secured in place.

 

[[email protected]]

But there is an intrusive noise associated with this pulley , once a
revolution.

"...once a revolution." of what? The platter or the pully?

If the platter, you likely have a microscopic fault in the center
spindle-bearing or belt contact surface. If the pully, likely a flat
spot in the bearing(s) for it. Try REALLY cleaning the spindle
bearing, and try a slightly tighter drive belt (band). Look for even
the slightest cant on either the platter or the pully. If the top/
bottom edge of the pully grabs at some point that would explain it.
Also, clean the belt bearing surface on the platter thoroughly.
Running over it with 1200-paper or 0000 steel wool (some great
distance from the rest of the electronics and clean afterwards
thoroughly) may also remove nearly invisible faults.

Aside: I have never understood the appeal of B&O stuff - far too much
was sacrificed to "design" vs. engineering and function. Ah, well.

Peter Wieck
Wyncote, PA

 

[N Cook]

"...once a revolution." of what? The platter or the pully?

If the platter, you likely have a microscopic fault in the center
spindle-bearing or belt contact surface. If the pully, likely a flat
spot in the bearing(s) for it. Try REALLY cleaning the spindle
bearing, and try a slightly tighter drive belt (band). Look for even
the slightest cant on either the platter or the pully. If the top/
bottom edge of the pully grabs at some point that would explain it.
Also, clean the belt bearing surface on the platter thoroughly.
Running over it with 1200-paper or 0000 steel wool (some great
distance from the rest of the electronics and clean afterwards
thoroughly) may also remove nearly invisible faults.

Aside: I have never understood the appeal of B&O stuff - far too much
was sacrificed to "design" vs. engineering and function. Ah, well.

Peter Wieck
Wyncote, PA

The noise is from the intermediary idler pulley, once per pulley rev.
Agreed about B&O, it got even more silly with record decks, effectively
weighing the records to automatically set the speed and arm drop positions
automatically.
I've run a strip of stretched moped inner tube around the edge and glued in
place to see what happens to the noise

 

[N Cook]

The noise is from the intermediary idler pulley, once per pulley rev.
Agreed about B&O, it got even more silly with record decks, effectively
weighing the records to automatically set the speed and arm drop positions
automatically.
I've run a strip of stretched moped inner tube around the edge and glued in
place to see what happens to the noise

The noise was coming from the (forgotten the mechanical name) the pulley
that engages with the pin/plate that is moved on adjusting the speed. That
shift pulley coaxial to the idler pulley, so moving the idler up and down
the drive cone bobbin, for speed change.
There was a tiny nick and gouge out of the aluminium of the active surface
of that "gear-box shift" pulley so flexing the plate on each revolution.
But at least I know that moped inner tube dodge works should anyone faced
with a broken /totally worn thin idler edging.