Help Tektronix 466 repair advice

Discussion in 'General Electronics Chat' started by epicfatigue, Mar 20, 2013.

  1. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    Hey everyone, i am getting into electronics and have been toying with them for the last 8 months.
    I have repaired 3 CRT arcade monitors thus far so by basic recapping and fault finding,

    However i am alittle stumped as to where to start with this.

    I brought it to learn how they work and gain some experience however i think it is broken i have taken a video of its symptoms if someone can point me in the right direction that would be fantastic, i pulled it apart to have a quick look and this thing has caps that are massive!


    The Manual is here.
    http://www.ko4bb.com/manuals/index.php?dir=Tektronix/Tektronix_-_465_Oscilloscope

    The one thing i want to know before i go diving into this is how i discharge it.
    I can not see an anode cap!
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,986
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    Looking at the power supply diagram on section 12, check that all supplies are there first, this is the best place to start looking, then see what happens when the beam finder button is pressed.
     
  3. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Not that there aren't a lot of good folks around here but you should check out the Tektronix Yahoo group. Those guys eat, sleep and breath Tek.
     
  4. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    fantastic i have just joined there group, i shall test this tonight when i get home cant wait to get this thing working.
     
  5. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    Hey everyone,

    First off I LOVE TEST POINTS that made it so easy!


    So here are my results for test points

    Expected Result
    +65v +65.12v
    +15v +15.05v
    +5v +5v
    -8V +0.71v
    -15v -15.18v
    +140v +139.80v


    So it appears the -8V is where we start hunting!
     
  6. Sue_AF6LJ

    Member

    Mar 16, 2013
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  7. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    That is good news.

    I had a similar issue one of my voltages dropped out. Can't remember which. Turns out it was a bad op amp in a very accessible place. I understand it is a common problem.

    I have a 475A power supply schematic. Not sure if it is the same. But I promised not to share it anyway since the person that sent it to me makes his living off of selling them.


    If the 475A is anything like the 466 you should check for 464A. If you find it you might just consider trying to swap it out. It is a common op amp that you will find at Radio Shack.

    There really is not that much to that circuit. One op amp and 3 transistors.
     
  8. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Well did you get this. working?
     
  9. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    nope only just found the diagram for the power supply there is a few things in there will be checking them out over the next few days.

    mostly transistors. just need to look up how to test them correctly
     
  10. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    okay so i finally found the correct diagram,

    Layout is Page 275

    And Power Supply & distraction page 292

    I have highlighted all the components and i am going to remove them 1 by 1 and test them there is only a total of 17 components

    3 transistors
    5 capacitors
    7 resistors
    1 VR resistor
    1 op amp


    Was thinking about testing them in that order.

    [​IMG]
     
  11. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Take a look at that opamp. It was what was wrong with mine and I understand a common point of failure. It's easy enough to swap out as it should be in a socket.
     
  12. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    yeah i did have a look at it, its not in a socket on mine,

    However is appears that the input voltage to generate the -8 is incorrect.

    Leads me to believe its a component further upstream.
     
  13. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Do you have the 50V? You should if you have the other voltages. It could be on mine it was replaced before and whomever repaired it put a socket in.

    Do you have that 3.8V?

    I'd take all of the voltage measurements and post on the Tek yahoo group.

    I sure hope it is not the filter cap. Those babies are really buried. But they probably should be replaced anyway.
     
  14. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    Hey most of mine are in sockets, it could be whoever replaced this didnt put one in?

    Who knows ill put a socket in it anyways.

    yeah i am praying it is not c1771 that baby is massive, 5500uf
     
  15. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Sadly that cap will need to be replaced soon anyway. It is probably long past due unless you are sure it has been refurbished in the last few years. It is not so bad that it is big but how it is buried and soldered in that pcb.

    This is a reason why I sold my 475A and bought a digital scope since I am mostly doing digital anyway. I have replaced some fairly large caps in the past but they have always been mounted on a chassis and in easy reach. I would not want to replace those one.

    Figures all but the suspect chip are on sockets. :(
     
  16. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    The caps are easy to replace for me take a few minutes the real issue is replacing the 8pin socket as that i have to dismantle the pcb to get to.

    No issue though my time is free and the chip is $00.50 however the large filter caps will be alot i assume
     
  17. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    She lives have not tested it but i have a trace line now!

    Bad transistor and op amp!

    [​IMG]
     
  18. spinnaker

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    Oct 29, 2009
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    Very cool. Now who told you it was the op amp? :)
     
    epicfatigue likes this.
  19. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    you and my circuit diagram!

    Hahah thanks for the heads up though, i did move it up on my list of things to test.

    Transistors then the opamp didnt bother about the others.

    I have a green line but i still do not know if it is working correctly,
    going to have to find a training manual or somthing that can teach me how to use them with some labs.

    Know of anything like this?
     
  20. epicfatigue

    Thread Starter New Member

    Feb 22, 2013
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    well that was short lived was playing with it testing it, pressed the store button, now i have lost the trace again....

    checked the psu everything checks out...
    All the voltages are there guess something died further
    Any subjections ?
    https://www.youtube.com/watch?v=tXx0g8OF3QI
     
    Last edited: Mar 27, 2013
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