Vestax pcv-002 clone

Discussion in 'General Electronics Chat' started by El Zu, Feb 6, 2016.

  1. El Zu

    Thread Starter New Member

    Jan 13, 2016
    16
    0
    Hi!

    I'm trying to clone vestax pcv-002 from original circuit. Made the PCBs, but it doesn't work properly. The volume is low, pots doesn't much effect the sound (completely turned down pots still sending signal) and phones doesn't work as well.

    I've checked the pcb and everything is connected right. But I find out that semiconductor 2sc1627 is to weak to supply U19 and phones pcb part. This gonna make me crazy about this circuit.

    What should I check or re-check, to find the problem?
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    Dont see the point of that transistor, its just an emitter follower, what happens if you short the C/E out,?
     
  3. El Zu

    Thread Starter New Member

    Jan 13, 2016
    16
    0
    Its quite clear, I short the C and E out and U19 starts working, it sounds louder, as well as monitor amp (U7) but the voltage is to high and it distort the sound in phones. C is 15V and E is about 1,3V.

    You see, the solving problem with the transistor doesn't mean the solving problem of the whole circuit, but think it is the result of the main bug.
    I surmise thats its all about GND or supply in general.
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    Change the transistor for a Bd131 or Tip121 Darlington, maybe a Zener diode on the base.
     
  5. El Zu

    Thread Starter New Member

    Jan 13, 2016
    16
    0
    Thanks, I try it.
    But the question is why the original circuit doesn't work as it should be. Changing the transistor or supply part doesn't solve the problem with pots (i use this http://lib.chipdip.ru/995/DOC000995779.pdf). I think something is causing all this problems, but can't find it.

    UPD: Strange thing happen - if i totally disconnect GND2 point on H2C/CN2J the LED11 (Power Led) is still working (while the pwr is on). How it can be explained, there is no any GND connection on this board.
     
    Last edited: Feb 10, 2016
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