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Needing Tektronix 516 Oscilloscope Troubleshooting Assistance

Discussion in 'Troubleshooting and Repair' started by Northir, Mar 1, 2011.

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  1. Northir

    Northir

    2
    0
    Mar 1, 2011
    I have a Tex 516 that i got from the local goodwill, and i cant seem to get it to give me a wave form on the screen i set it up exactly how the manual says to in the step by step first time use part, all the components inside look all right, no burn marks and nothing is deformed, it will stay on for as long as i like, i did replace the fuse, but i couldnt get the exact spec so i had to go .2 amps low, and twice the voltage, 117v 3.2 amp time delay, i used a 250v 3.0 time delay, as it was all i could come up with, it is tube based, and i really dont want to think the cathode is bad, but it doesnt look like the cathode is even turning on or getting power, any thoughts you guys might have would be awesome
     
  2. shrtrnd

    shrtrnd

    3,717
    469
    Jan 15, 2010
    I assume you mean a Tektronix 516. I don't have a manual on that.
    Are there any other lights in the face display, any way to see if the instrument is getting power, and not just the CRT?
    Typically in old scopes, the power supply is the problem, usually the big electrolytic capacitors dry out, and the instrument won't work.
    I don't know what you know about troubleshooting. Always stay clear of the anode plug to the CRT. Even if it's not plugged-in or turned on, (which can be lethal if you don't know what you're doing), the CRT itself stores a large voltage charge).
    If you think you're competent to troubleshoot. I'd start checking the power supply voltages. You didn't say if you have an operator or service manual. But often the voltages are shown on the printed circuit board itself for different test points.
    If you're a newbie, I'll warn you again, the voltages on that CRT anode are extremely dangerous, and you don't want to mess with them.
     
  3. davenn

    davenn Moderator

    13,560
    1,856
    Sep 5, 2009
    Most tek scopes (particularly the older ones) have a trace (beam) find button.
    very handy to check and see that the tube is ok but the the trace positioning is out of whack and off screen.

    look in Ebman for tek manuals amonst other places online. Tek manuals have very good service info with good fault finding flow charts etc

    Also, Im a member of the Yahoo tektronix scope group its a great place for info
    they have huge archives of questions and answers covering many many different models

    Dave
     
  4. Northir

    Northir

    2
    0
    Mar 1, 2011
    yes im well aware of the amount of power in the unit, just out of general curiosity i took a inductive voltage pen and checked some circuits and its got enough power to set off the pen about 6 inches away from the unit,

    the issue im trying to fix is the fact that i cant get the display to turn on, the entire unit powers up, but i cant get the crt to display, there isnt a trace beam switch or button only a horizontal positioning dial, which ive already tried fiddling with

    there is not a single PCB in this unit, that i can find anyways, its all ceramic plates and lengths of exposed wire, all though i do have the stock manual

    this is the unit
    http://s38.photobucket.com/albums/e121/ZeroGateway/Oscope/
     
  5. shrtrnd

    shrtrnd

    3,717
    469
    Jan 15, 2010
    Hope you get a manual.
    My guess would be a bad CRT itself, or bad High Voltage supply to CRT (big electrolytic caps the ususal suspect).
    Did you look at the CRT yoke when the power is on? Do the filaments light when the power is on? Do you HAVE voltage to the CRT filaments?
    If you've got light in the CRT filament, (Sounds like you might have the HV), X & Y deflection circuits might need to be checked. Like davenn said, Tektronix manuals are pretty good. And test points inside the chassis are usually pretty-well marked, if you want to start checking test point voltages, to try to isolate the fault.
     
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