BeoGram

Re: Beogram 8000 Cuing problem

Dillen — Wed, 08 Apr 2009 02:44:21 GMT

... I see evidence that the motor possibly may be trying to make tiny, slow movements
to move the stulus slightly further in...

Exactly !
The tonearm is moved towards the record, just full speed ahead - no counting.
When a record is sensed, the tonearm is positioned at the record edge. Then a pre-decided further amount
of pulses is counted at a slow speed to position the tonearm exactly over the lead-in grooves.
First when the exact number of pulses are accounted for, the arm is lowered.
Your belt will be too tight or have a wrong elasticity. The OA 3.3 belt you mention in the other thread is
a standard round belt and I'm afraid very far from useable here.
I have suitable belts in stock. Not V-shaped as the original but with suitable elasticity and size for the task.
I'm sure that if you remove the belt when the tonearm stops, the motor
will start running slowly, attempting to reach the correct number of pulses from the optics and if you
turn the threaded shaft by hand, the count will eventually be correct and the arm will lower.
This will confirm the diagnose.

The diagnose for this symptom, we've had it countless times here, will be a worn or wrong belt and/or
the threaded shaft and bushing will need cleaning/lubricating. Often both.
The correct belt will have very little elasticity (we're on margins here).
Fresh silicone grease is good for lubricating the threaded shaft, also at its plastic holder.

...while playing as the arm is slowly moving across the record, the motor and gear (belt) do move in
a slightly jerky fashion (short starts and stops) the whole time. Is this normal?

Yes, that's normal for all B&O tangentials.

Martin

Re: Beogram 8000 Cuing problem

fidocat — Tue, 07 Apr 2009 21:03:01 GMT

Hey folks,

I have the same problem as Andy with my Beogram 8000. It cued OK before I replaced the belt. Now with the new belt it still cues up in the proper place but it just won't move down onto the record. Perhaps I jarred something during the process. I found that by bending the backstop switch I was able to directly affect where the stylus stopped while cuing. As an aside, I tried simply rotating the switch assembly by loosening the large philips screw which fastened it to the chassis. The switch got quite loose but it still wouldn't rotate. It seems to be held in place by a pin or something in the chassis. But no matter, bending allowed me to precisely adjust the starting location.

Anyway, I've found two work-arounds but they're both inconvenient so I'd like to fix the root of the problem. First work-around: I hit play, it cues and stops. I then hit the "<< <" button for a fraction of a second, (the tone arm doesn't actually move since it's just a momentary pressing). I then press Play again and the stulus properly moves down and plays normally. Second work-around: I press play, it cues and stops. I then manually rotate the worm-gear approximately 360-degrees (never very much more or less). At this point, the servo takes over and it drops down and plays normally.

Edit: I'll mention again that it doesn't seem dependent on how far the tone arm moves (ie, adjustment of the switch). For example, I put a pen cap on the switch to cause it to cue several millimeters further, way past the lead-in groove. But the stylus still wouldn't move down.

I've inspected the mechanism closely. The belt doesn't seem to be slipping nor is it too tight. I see evidence that the motor possibly may be trying to make tiny, slow movements to move the stulus slightly further in. This is hard to see but every once in awhile I see it move slightly. I totally cleaned the worm gear with solvents and a plastic brush, then lubricated with fine machine oil. It seems to move fairly smoothly and the motor doesn't seem to be straining. Another observation, while playing as the arm is slowly moving across the record, the motor and gear (belt) do move in a slightly jerky fashion (short starts and stops) the whole time. Is this normal? Any ideas?

- Chris

Re: Beogram 8000 Cuing problem

Andy — Thu, 22 Nov 2007 04:31:05 GMT

Thanks for all your help well I did as Peter suggested unscrewed the cross screw and wiggled and jiggled the so switch not having a clue what was happening tightened the screw tested on a LP and guess what perfect cueing!! I dont know what ive done or how but it worked!

However still doesnt cue properly for a 7 inch but I dont play them much.

Thanks again

Andy

Re: Beogram 8000 Cuing problem

Dillen — Tue, 20 Nov 2007 07:06:44 GMT

You are right about the counting though I am not quite sure when it counts or if it just checks for pulses.
At the end of the record, when in the lead-out groove, the CPU merely detects that the pulses are coming in fast.
The SO switch, I think, is there only to tell the home position (See EDIT below). At start the carriage is moved inwards until a record is
sensed and then, slower, a bit further. I am not sure if this last slow movement is simply timed or it actually counts pulses. (See EDIT below)

If paused during play and then asked to continue, the Beogram will hit the exact same spot again so that will
have to be a count.

It doesn't count during play. If the belt is lose and the carriage doesn't move according to the grooves, the Beogram will never find out.

Martin

EDIT:
I had Friedmett's Beogram 8002 on the bench last night and, after doing a few repairs, it provided a good opportunity to check this.
I found out that it actually counts the pulses when moving in slow towards the lead-in groove.
I also checked the manual and it tells about the SO switch as being the point for adjusting where to lower the arm so Peter was right again.

The sensor in the arm is merely to detect record size and presence thus preventing a lowering where no record is present.

Re: Beogram 8000 Cuing problem

auric — Mon, 19 Nov 2007 21:18:41 GMT

Martin:

Doesn't the 8000 count the rotations to determine where to stop the cue arm?

If the belt slips the motor will turn more but the optical encoder will still count the same number of pulses thus it should always still cue properly. I'm curious why this isn't the case. (I don't know)

To test this theory maybe cue the arm manually to some point on the LP. Leave the arm there and after some period of time the Beogram should send the arm back to rest position. If you hit play, the arm should return to the cue point. I'm wondering if it will find the cue point correctly. If not will the offest be by the same as the offset that is experienced now?

Just some thoughts...

Derek

Re: Beogram 8000 Cuing problem

auric — Mon, 19 Nov 2007 21:09:14 GMT

Hi Peter:

I would add also using a coin (depending on which country you are from; some may be too thick) or a big fat butter knife to remove the panel under the tone arm. Using smaller screw drivers will leave marks on the plastic.

Be creative and don't be lazy! Keep these things beautiful :)

Derek

Re: Beogram 8000 Cuing problem

Andy — Mon, 19 Nov 2007 17:59:40 GMT

Thanks

ive already done what Martin suggested and replaced the belt because the arm wasnt moving well this has helped. i will try the SO this now makes a bit more sense when looking at the diagram.

ps ive lots of spares for this beogram and the 6006 if people are in need!!

Re: Beogram 8000 Cuing problem

Peter — Mon, 19 Nov 2007 17:31:40 GMT

Though I would do what Martin says first!!

Re: Beogram 8000 Cuing problem

Peter — Mon, 19 Nov 2007 17:30:33 GMT

I think even your least technical moderator can help here!! Just had a little poke around! I take it you have Page 5-3 of the manual. Obviously working out what you are looking at is the challenge!! To see this, all you need to do is remove the black panel under the arm. To get there, set the arm off to over the platter and stop it there. There is a big plastic screw at the front end of the plate. rotate this using the biggest bladed screw driver you can - the plastic is soft and tears otherwise! The plate with then lift off and the picture showing the SO switch suddenly becomes clear!! There is a big silver Philips screw which will need loosening and then some fine movement should so the trick! let us know how you get on!

Re: Beogram 8000 Cuing problem

Dillen — Mon, 19 Nov 2007 17:16:13 GMT

Probably in need of lubrication. The threaded carriage shaft will need cleaning and a couple of drops of acid-free oil (sewing-machine oil).

Could also be the servo motor belt slipping.

Martin

Beogram 8000 Cuing problem

Andy — Mon, 19 Nov 2007 16:07:29 GMT

my beogram 8000 has stopped cueing in the right position both with LPs and 7 inch it drops the arm about 2mm short straight onto the platter!

Is it easy to adjust?? I have the service diagram but cant work it out!!

Thanks

Andy