Beogram 4000 needle lifting

[beosince]

Dear Beoworlders,

quite some time since I have posted here. My Beograd 4000 has developed an odd fault. When I start playing a record, it sometimes happens that the needle lifts for just a fraction of a second (I can hear the click), and then it instantly drops again. It only happens at the beginning of a record, and never further down the record. I measured the Voltage across the solenoid and that was 3V. Any ideas?

• This topic was modified 2 weeks, 2 days ago by beosince.

[Mark-sf]

Welcome back. I’m not sure I understand you issue from your description. Are you say that when you press start the arm moves to the record edge, lowers then comes up and lowers again? Or is it doing something else? When it drops again is the solenoid actuating again? Perhaps you can upload a video.

[beosince]

I have taken a video of it happening. It only seems to happen in the first 1/3 of the vinyl, mainly in the first two songs, never later.

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[beosince]

Here is a link to view the video as well: https://vimeo.com/1137451595?share=copy&fl=sv&fe=ci

[Mark-sf]

You really need to take a look at the service manual in the section that discusses the adjustment of the magnet coil. That is where I would start before investigating failing parts. Rudy’s Beolover site also has a complete 4000 restoration that covers that area well: https://beolover.blogspot.com/2024/02/beogram-4000-full-functional-restoration.html.

[beosince]

I have done most of the things mentioned in the blog post today (cleaned all contacts, cleaned and lubed everything appropriately, re-aligned everything). However, the symptoms persist…. any ideas? It only happens at the beginning of the vinyl. If I press the up button before the needle drops for the first time and start the record further to the centre it does not happen.

[Mark-sf]

If you move the arm from the off position directly to the lead-in groove, not relying on the automatic edge detection, and manually cue it down, does it play properly?

[beosince]

No, it happens also when I cue the record manually.

[Mark-sf]

If that is the case then there must be in inner point in the record where that stops occurring. Is this the case or is it simply having to cue it down a second time that allows it to continue to play? Why this is critical is that there may be something that is causing the solenoid’s arm to withdraw. The circuit switches to a lower current setting to hold it extended which makes it susceptible to being bumped to release. As such I would try it with the outer platter removed and starting it. If it stays down, then you can very gently tap the cartridge inwards to see if it moves without raising until the end.

• This reply was modified 1 week, 4 days ago by Mark-sf.

[hcraig244]

When you say it only happens in the first 1/3 of the record does it always happen at the same point each time it occurs?

[beosince]

Mark-sf wrote:

If that is the case then there must be in inner point in the record where that stops occurring. Is this the case or is it simply having to cue it down a second time that allows it to continue to play? Why this is critical is that there may be something that is causing the solenoid’s arm to withdraw. The circuit switches to a lower current setting to hold it extended which makes it susceptible to being bumped to release. As such I would try it with the outer platter removed and starting it. If it stays down, then you can very gently tap the cartridge inwards to see if it moves without raising until the end.

I feel like it looses voltage for a millisecond which causes the needle to jump up. I dont have to cue it down again, it just jumps very shortly. I have tried to manually replicate this by trying to lift the arm at the mechanism, but the magnetic field is strong enough to keep the arm down.

[beosince]

hcraig244 wrote:

When you say it only happens in the first 1/3 of the record does it always happen at the same point each time it occurs?

No, it happens sporadically. I feel more so towards the very beginning of the record, and not often after that.

[Mark-sf]

I can’t say I’ve ever seen that particular behavior. Have you replaced all of the electrolytic caps? These can be the cause of intermittent issues and is required for a Beogram of this age.

[hcraig244]

I have found a number of these random intermittent faults have been caused by the switches feeding the logic gates within the control panel, the logic chips are very reliable and seldom, if ever fail….the switches feeding the gates however are very susceptible to fail…typically arc and corrosion, and also bending over time…if a leaf type switch is left stood in one position for a long time it will loose some of its elasticity. The switch that controls the lower current to the magnetic coil is one such switch, if this is not clean and fully functional it could cause the issue you describe, also clean and inspect the control panel switches….have a read of the training notes donated by Solderon in the manuals section of the products area…..they are very informative.

Good luck!

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