Beogram 4002 arm movement

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  • #8741
    orava
    BRONZE Member
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    Hello

    I have 4002 with DC motor (552x), and it has problem with “rewind”, fast backwards, movement. Looks like motor does not have power to do that. If I go to full stop, movement is fine. I have manuals but no shematics for this board version (see pictures). Can anyone tell associated transistors on this kind of board. 550xIMG_20220916_131555_1

    #8744
    Mark-sf
    BRONZE Member
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    I’m not sure I understand your symptoms. You say going to stop works fine but fast backwards doesn’t. Those functions use the same circuit except for how they are activated. Are you saying that the arm returns fine at the end of record but simply raises and doesn’t when you press Stop?

    #8749
    Dillen
    Moderator
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    That PCB needs a full restoration.
    It still has the original capacitors, which will be bad by now, and the original, now badly oxidated, trimmers.
    With all that still in circuit in can be difficult to point to a specific culprit component.

    Had the PCB been completely restored, and still failing, the reason could be a leaking diode or transistor.

    Martin

    #8784
    orava
    BRONZE Member
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    Hello

    Mark, I mean if record is playing, I press arm up and then fast backwards, it does barely move as there is not enought voltage on motor. If press stop, arm goes to home position at normal speed.

    Martin, I know, this board picture is from my “spare” machine, I do not know if it is even in working condition. Just so lazy I did not get actual board out of player.

    I do like to check transistors but witch ones? Of ourse I can check them all but to know will ease process.

     

    • This reply was modified 2 weeks, 3 days ago by orava.
    • This reply was modified 2 weeks, 3 days ago by orava.
    #8798
    Mark-sf
    BRONZE Member
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    “Fast” backwards,>>, is the same as Stop so I am still not sure what you are describing. How is the speed compared to moving forward between Play and Stop as well as < and >?

    #8810
    orava
    BRONZE Member
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    Yes it is, but difference is do I press up/down before it.

    #8841
    spassmaker
    BRONZE Member
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    Hi

    As Martin mentioned the best way to get the Beogram back to “normal” operation is a total recap.

    “STOP” and “ES” (End Switch) are causing the arm traveling faster than just pressing < or >.

    There are two potentiometers for the slide transport 1R61 and 1R62 which can be adjusted for the traveling speed while pressing < or >.

    Regarding to the service manual there is a plot underneath the Motor OM2 what measuremenst or voltages should be adjusted in all cases:

    ON >>

    << OFF

    <

    >

    So these potentiometers should be renewed as well, same for all other potentiometers, they tend to corrode and are hard to adjust to specs.

    Let us know if you got any progress.

    Kind regards

    Christian

    #8914
    orava
    BRONZE Member
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    Sorry all, I have talking rubbish (poor, poor memory).

    You are absolutely right, >> is weak, and does NOT depend any other keys.

    #8928
    Mark-sf
    BRONZE Member
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    This could be multiple issues including the servo belt, threaded rod alignment and cleaning/lubrication, loose or cracked pulley, etc. I would attack the mechanicals first before the electronics based upon an issue in only one direction.

    #9308
    orava
    BRONZE Member
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    Back on this for a moment…
    On DVM transistors (TR19-22) on “ON” side base voltage is when “>” 5V an “>>” 14v but on “OFF” side (TR23-26) both “<” and “<<” app. 4V.

    Also should 4IC1 collector be adjusted to 5V with R88, can adjust only to 6,5V min.

    #9388
    orava
    BRONZE Member
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    Reason for 4IC1 was bad aglinment.
    For slow carriage movement shorted D31 between slow back 3V adjustment and motor feed transistors.
    Next problem. Carriage motor wont stop at stop switch, and yes, switch is ok.

    #9455
    Mark-sf
    BRONZE Member
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    Does the turntable motor keep spinning as well as the lamps stay lit? If so, you still have an active 22.8v rail and OTR1 is not turning off. Is the anode of 1D1 grounded when this occurs?

    #9468
    orava
    BRONZE Member
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    Well, I do not have any 0TR1, I C1 I guess..

    As I say on first message newer board and service manual do not equal. Manual says “circuitry is basically identical” although layout and numbering is different. So I have to decode board with almost right circuit diagram.

    #9471
    Mark-sf
    BRONZE Member
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    No, a TR is not an IC. You will need to trace the circuit but you have the SO switch as a reference. Just follow its high side.

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