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VU build from a old tape deck.

Discussion in 'Electronic Repair Modifications DIY' started by Omen, Feb 21, 2015.

  1. Omen

    Omen Active Member

    Hi! I pulled this nice set of VU meters from a old nakamichi tape deck. The deck powered up but I think the belt was shot. Any way I was going to build another set of VU's for a mate. I was stoked that I only had to unscrew two screws and the whole VU module popped out. I hooked up some power and the lamps fired up! Good start! I tried to get some 1kh test tone signal in from my 02R in to it. I can get the needle to move a little on each meter but not much. So I know which cable is left and right and I assume that the only cable left would be the - cable. Another funny thing happening is when I turn up the gain on the test tone the needle goes down more not up!
    Maybe you can see from this photo wot I'm doing wrong. I'm using my JLM VU meter kit I built as a reference but it's not happening. Cheers
     

    Attached Files:

  2. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    A needle going down seems like a gain reduction behaviour to me ;).
    The reactions you get can be very different depending on the polarity and how much electricity the unit is suppose to receive to react correctly.
    The best thing is to analyse the power that goes to it in it's original use and/or start from the schematics.

    I guess the best one to guide you on this is @Boswell
     
  3. Boswell

    Boswell Moderator Distinguished Member

    What's the meter reading with no signal input? Does the needle "go down more" in proportion to the signal level, or does it only start to go down at a certain amplitude of input?
     
  4. Omen

    Omen Active Member

    Thank you Boswell and Pcrecord for taking the time to help.

    I put a multi meter over the power pins on the tape deck that the clip came off and it read 11.94 dcvolts. So 12volts. I'm using a 12volt power supply.

    The meter is reading at below -40 with no signal and starts going down when I turn the test tone up from -20db and more. So it does only start to go down at a certain amplitude of input.
     
  5. Boswell

    Boswell Moderator Distinguished Member

    I'm sorry, but I don't fully understand what you are describing. Are you saying the meter reading stays at or below -40 with all signal levels up to -20dBu and then (somehow) goes lower than that for signals greater than -20dBu? Are there any input signal levels for which the meter goes above -40?
     

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