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Need circuit of Power Supply 110v Tektronix 475A Option 4

Discussion in 'Troubleshooting and Repair' started by Global111, Nov 28, 2018.

  1. Global111

    Global111

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    Nov 28, 2018
    I'm trying to restore the oscilloscope Tektronix 475A Option 4
    I found on the Internet a good documention for the oscilloscope 475
    However, my instance is different (Option 4)
    I found documentation on the opton 4 circuit but it is of low quality
    Can you send me a picture of a 110 volt channel circuit ?
    My instance has Q1497 transistor (protection of Q1496 current)
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,213
    1,856
    Nov 17, 2011
    Ah tose good old days when manufacturers actually published the schematics of their designs as part of the manual.
     
    davenn likes this.
  3. Global111

    Global111

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    Nov 28, 2018
    I'm interested in the document:
    tektronix 475 option 4 maintenance manual
     
  4. 73's de Edd

    73's de Edd

    2,677
    1,085
    Aug 21, 2015

    Sir Global 111 . . . . .


    O.K. you can forget worrying about the Option 4 design aspect of that unit, as I am certain that you are not going to be one of the very-very-very select few (x the power of 100) that would be be needing the additional RFI and EMI suppression of that unit unless being in a RFI EMI anechoic chamber / screen room and, even then, be using its DC powering option.
    So this Option 4 unit is giving you MORE radiation suppression than the common version does.

    As far as the units + 105V supply , it is tied / interlocked into some adjunct supplies being active also as I have marked it up on the schematic..

    TEK RELEVANT SCHEMATIC:
    [​IMG]

    73's de Edd
    . . . . . . . . . . .



    I don't care HOW nice and fragrant the soap in their hand dispenser smells . . . . . you should never, never walk out of the rest room sniffing your fingers.
     
    Richard9025 likes this.
  5. Global111

    Global111

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    Nov 28, 2018
    Hm maybe I was wrong about Option 4 (Maybe other option ).... I need circuit wit current protection on Q1497
     
  6. 73's de Edd

    73's de Edd

    2,677
    1,085
    Aug 21, 2015
    Sir Global 111. . . . . .

    NEW SUPPLEMENTAL SCHEMATIC . . . .

    On the supplies specified schematic just below, note that the Q1496 is being the primary
    series regulating pass transistor, with a Q1497 being a current sensing transistor in its base circuitry and the Q1494 and Q1490 being go-no go sensing of the 50 V supply presence.

    PROBLEMS. . . .

    If you have problems with Q1496, it could try to not regulate and pass the full +136 supply voltage thru to the +110 supply . . .or . . . . a crunched C-E junction on the Q1497 could do the same thing.
    With Q1494 and Q1490, being so highly resistively isolated, they are being more bullet proof.

    THEN . . . . .

    Find the schematic page with with CRT support circuitry on it and observe the top left corner, where the +110V supply feeds in, and then the immediate Q13XX + CR13XX series related parts that it feeds for Z axis circuitry.
    See if any bad parts there are responsible for a shorting or excess current pull of your +110V supplies power input feed.
    Its 4 different supply routes being fed, are being shown on the schema snippet.

    Also, poor bypassing being provided by a main E- filter(s) could also be at fault, at the +50 and +105/+160 source of their raw DC filtering . . . . .C1412 - C1414 - C1428.

    (Maybe other option )

    The other option is being a " 7", which enables its electronic inverter to be powered up from a 24VDC power input source



    Here 'ya go . . . now all at no extra charge to you . . . as

    upload_2018-11-30_1-15-49.png


    73"s de Edd
    . . . . . . . . . .


    I accidentally swallowed a whole ice cube yesterday and haven't pooped it out yet . . . . now I'm getting really-really scared, you guys.

     
    Last edited: Nov 30, 2018
    Richard9025 likes this.
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