sonavor wrote:

Did someone move the tonearm counterweight too close to the tonearm base so it won't pivot down?

Hi sovanor,

Me and my Beogram needed a break from each other. Now, I'm back.

The tonearm counterweight was the issue. Someone (me) adjusted it a while ago to obtain zero force adjustment ('Static balance' according to the Service manual and Beolover's video

Hi Per,

So that was the source of the stuck arm problem, right?
Now that is resolved.

You will have to post a reassessment of what is not working at this point so reorganize and see what the next step is.

-sonavor

Hi sonavor,

Correct. Perfect balance is unfortunately very close to whenthe tonearm base is too close to the counterweight. Slightest move of the adjustment screw, and the arm is stuck. Anyway...

Well, current status is that error #5 is back again.

Same as in my very first post here, I was about to adjust the tracking force using the tracking force gauge. I pressed ON, tone arm moved to 30cm position, and lower. Then I used > to move the tonearm back for the adjustment. It was possible to start moving it back, but not stopping it. When pressing forward (>), it just stopped for a split second, end then continue back home. And after that Error #5 seems to be permanent again.

In Dec 1 you suggested Electrically, measure the DC voltages around 1TR25 and see what they are when the  /Q0 is a logic "0".

So now I did:

C: Varies each time I press ON. I got 16V, 2V, 10V, 5V, 1.3V.

B: 0.6-0.7V

E: 0V

Per

Hi Per,

It is curious that this error comes and goes. That makes me think there is something mechanical, something moving that causes the problem. I am also thinking about the fact that the turntable supposedly was in working condition and something during shipping caused the failure. We will eventually figure it out. You might have to dig into the Beogram button control panel.

When you press ON and the Beogram starts you should see a constant voltage on the collector of 1TR25 that would be instructing the servo motor to drive forward until the first set down point. It still sounds like there is a signal telling the Beogram that it is supposed to be turning off or telling it to be in fast reverse mode.  I believe you said that when you manually move the tonearm where it would be over the platter and then turn power on that the Beogram immediately returns the arm to the stopped/home position.  It would be interesting to monitor the collector voltages of both 1TR25 and 1TR34 at the same time with an oscilloscope. 

Regarding the tonearm balance though. The counterweight should not interfere with any movement of course. 
A couple of questions about your adjustment.
Were you making the zero balance adjustment with the tracking force knob set to zero? 
Were you making the zero balance adjustment with a phono cartridge attached?

A cartridge has to be mounted on the tonearm and the knob with the spring tension for the tracking force needs to be down at zero when starting the adjustment.

The result should be a balanced arm that has freedom of movement within the range that the Beogram would be playing a record. Horizontally and vertically.

-sonavor

I may be barking up the wrong tree, but I noticed on the last  picture (marked in red) where the PCBA board is lifted, would it be possible for the diaphragm be out of adjustment and forcing the tone arm to run backwards, as it was made to do on the 4000?

Keith.

Hi Keith,

From what has been described about the failure it doesn't sound to me like a problem with the tracking sensor diaphragm. I say that because the problem happens before the tonearm lowering event occurs. The signal from the tracking sensor shouldn't be a factor at that point. 

If it is somehow related then there is also a problem with the Beogram logic not knowing what mode it is in.

I still suspect the problem is related to one of the items that came loose during shipment of the Beogram.

-sonavor

Hi sonavor and Keith,

Happy new year! And thanks for your interest in my Beogram! I'm very grateful for this, I can tell you. I hope the below information can give you some clues. Please let me know =)

I manage to borrow an oscilloscope today. Collector of 1TR25 is on Channel 1, and 1TR34 on Channel 2. The short minus voltage at the end of each reading is when home position is reached and the relay shuts the Dane off. 1TR25 seems to be active when the Slide moves to the left, and 1TR34 when the Slide moves to the right.

• Here are 3 images when pressing ON, with Slide in home position, aka Error #5 (The channels together in first image, and 2 images with each channel separated):

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• Here are two images when pressing ON, but with the Slide firstly manually moved over to the outer edge of the platter before starting.
  (First image with same oscilloscope settings as above, as reference. Second image with Channel 1 zoomed in a bit, in case the initial spike is of any interest):

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Regarding the tonearm balance:

Were you making the zero balance adjustment with the tracking force knob set to zero? -Yes, I did.
Were you making the zero balance adjustment with a phono cartridge attached? -Yes, and without the protection.

After adjustment the arm is again free-moving. Just very close. See picture:

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Regarding the tracking sensor diaphragm.

Would it be possible that error #3 and #4 is related to it?

All the best,

Per

Hi Per,

I am afraid it has been too long away from this problem that I can't remember the problems by their number. Please restate the problem when referring to it so it is in context with each post. Otherwise it is too much back and forth looking up what the numbers go with in the thread. It is probably easy for you to remember but many of us are working on multiple projects.  Thanks.

I would like to see the activity on the transistor base leads.  In addition it would be good to use both of your oscilloscope probes to look at the forward and reverse signals on the motor itself...nodes where the emitters of 1TR28 & 1TR29 connect along with the nodes of 1TR31 & 1TR30.
If you see signals trying to drive the motor to reverse and stop then you need to track down what is driving those control signals. 

On your tonearm and counter weight. The weight assembly is away too close to the back of the tonearm. It has hardly any room to move.

-sonavor

Here is what my Beogram 4000 tonearm counter weight looks like from the side. It is balanced and calibrated so the tracking force knob is at 1 gram with the mark shows that it is at 1.

Hi sonavor,

OK, I'll include the error descriptions in each post from now on.

• Base of 1TR25 is on Channel 1, and 1TR34 on Channel 2 during Error #5*:

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• Emitter of 1TR28/1TR29 on Channel 1. Emitter of 1TR30/1TR31 on Channel 2. All during Error #5*:

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Tonearm counter weight

I don't know what I will do with that information.  

Per

* Error #5: At ON, Slide moves ~1 cm to the left, then returning home again (https://youtu.be/HG-VJ3dCZc0).