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Latest post 08-31-2010 1:51 AM by yachadm. 3 replies.
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  • 08-24-2010 1:28 PM

    • yachadm
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    BeoGram 4002 6000 (AC motor) capacitor

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    On the AC motor units, there is a large transistor next to the motor - a 2N3055 - this is 0TR1 in the SM.

    On this transistor is a ceramic capacitor which appears to be connected between the Base and Collector.

    This capacitor does not appear in the SM.

    On the unit I'm working on, this is broken, and I cannot identify what capacitance it is.

    I presume this is to reduce oscillation, but how important is it really, if it is missing?

    Menahem

    Learn from the mistakes of others - you'll not live long enough to make them all yourself!

  • 08-24-2010 1:34 PM In reply to

    Re: BeoGram 4002 6000 (AC motor) capacitor

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    Mine doesn't have a cap there (and I see no traces of one having been there either).

    Can't be too important... but I always use 100 nF for everything Big Smile

    -mika

  • 08-25-2010 8:33 AM In reply to

    • yachadm
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    Re: BeoGram 4002 6000 (AC motor) capacitor

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    Thanks Mika,

    But I'd really like to be sure of this from someone who has one with a cap, and can tell me what is is ;-)

    Menahem

    Learn from the mistakes of others - you'll not live long enough to make them all yourself!

  • 08-31-2010 1:51 AM In reply to

    • yachadm
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    Re: BeoGram 4002 6000 (AC motor) capacitor

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    I ran a couple of tests - I put in the following capacitors (polypro 100VDC), and scoped the oscillations at 0TR1 collector
     
    No capacitor - medium oscillations
    10nf - bad oscillations
    22nF - bad oscillations
    47nF - medium oscillations 
    100nF - slightly less oscillations than no capacitor.
    220nF - no improvemnt over the 100nF
     
    I left the 100nF installed.
    Other members advised me that they also don't have a capacitor there.
    I'm going to hazard a guess that the capacitors were present on the early production units with the older square-type transistor, and when (on later production units) there was an Engineering change to the 2N3055, the capacitor was no longer required.

    Learn from the mistakes of others - you'll not live long enough to make them all yourself!
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