What is this coil / inductor / transformer

Discussion in 'Electronics Resources' started by georgedb, Mar 11, 2019.

  1. georgedb

    Thread Starter Member

    Jul 29, 2017
    35
    0
    I recently found a broken TI Speak 'n Spell (end of the seventies) which contains a speech synthesizer.
    The broken part was easily identified as there is a small PSU-board that generates the needed -3.5V and -12V from the 6V battery or power supply, which contained a completely fried transistor. I guess a wrong polarity or higher voltage adaptor was used.

    I cleaned up, checked and replaced some components, only to find out that some coil used, creates a short circuit. That coil is needed for generating the -3.5V and -12V.

    Does anyone have any idea what to replace it with,or what this component is and where to find it?

    See the picture, it is the component with "7 7" on it, it is round and it contains 10 pins. Here is a schematic, which is NOT the schematic of my version of the SnS and its TDK PSU, but the coils are drawn here as separate coils, which they are not. Sent mail to the guy from Furrtek, he doesn't know. The only other source (Datamath.org) doesn't know either. A schematic of my version cannot be found, and a BOM which includes some part number for that coil either. I have searched for that coil / inductor / transformer, checked for TDK, tried to find pictures through Google, but unfortunately, I have not been able to trace that crucial component

    . 20190127_125339.jpg

    20190126_115204.jpg

    This PSU board is actually a weird board, as it contains some logic for Start Up and Power Down, but also 2 isolated resistors for the loudspeaker.
     
  2. georgedb

    Thread Starter Member

    Jul 29, 2017
    35
    0
    Formy specific board(s), these are the details:

    TDK PSU:
    PCU-312B / 1033305-72

    Mainboard:
    1040675-13; revision "AK"
     
  3. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
    7,234
    1,741
    Are you sure this coil is faulty as any such coil is going to read very low resistance almost indistinguishable from a short on a standard multimeter.
     
  4. georgedb

    Thread Starter Member

    Jul 29, 2017
    35
    0
    I soldered it out before I replaced the burned transistor (the others measured ok) and all seemed connected, which made me think my measurements were not valid. I soldered it back in and replacement the transistor.Upon powering it, it consumed 2000mA, which is way too much. Then I measured actually for a short circuit between GND and +VE,only to find out it is short circuited. As you can see, the board is pretty simple. I should have measured that as a first thing... As all other active components were ok or replaced, caps were measured ok, my only suspicion now is that coil...
     
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