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  • Re: Beogram 4004 problem

    Update: Still working i.e. no more dragged stylus. It still lifts at an angle, since my leaf switch is detecting the solenoid return NOT the oil-damped lifting of the arm. It occurred to me that if the leaf switch fails (stays open when the solenoid returns) I would be in a MAJOR pickle, since the sled won't return... imagine trying to remove an LP with the sled stuck in the middle, how would you lift it over the platter pin with the arm in the way? So, I soldered a very small tilt switch - on
    Posted to BeoGram (Forum) by Doofer on Mon, May 31 2021
  • Re: Beogram 4004 problem

    Progress on the 'safety switch'. When R92 (see portion of schematic) is pulled high, the sled motor moves (relatively) quickly back to the start position. I cut the PCB track before R92 (see photo - PCB just to the left of the control switches) and soldered a switch in place instead. When this was closed everything works as usual. When the switch is open, everything works as usual EXCEPT at the end of the LP side the sled doesn't start moving back to the start position until this switch
    Posted to BeoGram (Forum) by Doofer on Tue, May 11 2021
  • Re: Beogram 4004 problem

    UPDATE. Apologies for the pause, I had to wait many weeks for my MC20EN to be 'renovated' after I had noticeable distortion towards the end of 12" singles. Finally it has returned (and now appears to be labelled 'MMC4000"... the murky world of refurbishment...) and can play the end of 12" singles without distortion. Anyhoo, I can confirm that demagnetization in situ @ 3V pk-pk, as described above... DOESN'T WORK. I note that just testing using the buttons all still
    Posted to BeoGram (Forum) by Doofer on Sun, May 9 2021
  • Re: Beogram 4004 problem

    The way the circuitry does the initial 'pull' at 30V then 'holds' at around 3V says a lot for the sensitivity to distance here! I guess it's no surprise that the circuit was designed to hold with zero separation between the components. The residual magnetization issue is considered to be to do with that physical contact, so it may be abolished by much smaller separations, but of course how physically durable would a washer 0.1mm (or less!) be in the long run? So you're probably
    Posted to BeoGram (Forum) by Doofer on Tue, Apr 6 2021
  • Re: Beogram 4004 problem

    Brilliant! Could you upload a photo, just so as I can see clearly what you did?
    Posted to BeoGram (Forum) by Doofer on Mon, Apr 5 2021
  • Re: Beogram 4004 problem

    Nice piece of work. I wish my workshop had spare Beogram parts lying around (!). Your efforts suggest that removing & disassembling the solenoid is not too tricky. That being the case, I wonder how hard it would be to replace the solenoid liner with something non-magnetic? As long as that remains potentially magenetisable, the residual magenetism issue will keep coming back. (Alternatively, if my method of 'demagnetization in situ' works - nothing conclusive to report yet! - I suppose
    Posted to BeoGram (Forum) by Doofer on Wed, Mar 31 2021
  • Re: Beogram 4004 problem

    Nor would replacing it from a dead 4004? This seems likely to be a problem that gradually worsens over time (years). Demagnetizing might sort it out for a while. Anyway, I've performed the following procedure: - de-solder solenoid at PCB - attach it to an oscilloscope (to measure voltage across solenoid) & the output of a small audio amplifier - connect sine wave signal generator to input of amplifier - from zero, turn up signal generator until +/- 1.5V across solenoid - push plunger into
    Posted to BeoGram (Forum) by Doofer on Mon, Mar 29 2021
  • Re: Beogram 4004 problem

    Undoubtedly
    Posted to BeoGram (Forum) by Doofer on Mon, Mar 29 2021
  • Re: Beogram 4004 problem

    When it's in the 'down' position, I measure 1.49V across the (10 ohm?) coil. So I'm thinking of de-soldering the live end, connecting it to a small audio amplifier with a signal generator attached, then supplying 1.5V pk-pk @100Hz or so for 30 seconds, then gradually turning the amplitude down to zero. This may of course not work in removing residual magnetization in the plunger, but more specifically is there anything I'm missing here?... before I do some damage!...
    Posted to BeoGram (Forum) by Doofer on Sun, Mar 28 2021
  • Re: Beogram 4004 problem

    I have this problem too. - Arm raises immediately if I press the right buttons on the deck - Carriage detects end of record and moves back to start - BUT sometimes there is a delay between the carriage starting to move back and the arm -> needle can be dragged several cm across the record surface before lifting. Sometimes the delay is very short e.g. the arm swings a few mm to the left as the carriage starts moving, before the stylus leaves the record. This is clearly the wrong order of events
    Posted to BeoGram (Forum) by Doofer on Wed, Mar 24 2021
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