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tektronix 2213 oscilloscope faulty trigger

Discussion in 'Troubleshooting and Repair' started by Terence123, Sep 17, 2012.

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  1. Terence123

    Terence123

    11
    0
    Sep 17, 2012
    Hi,

    I recently got my hands on 2 tektronix oscilloscope. (2213 and 465). Dived in the 2213 because it still shows an image.
    Everthing works ok except the trigger. Cannot get still image in auto trigger mode. In normal mode, i have no image at all (except a vertical line completely on the left of the screen). Also with ext trigger the image is running.

    With the "var hold-off" i'am able to get an almost still image with low frequencies (in auto trig) but it soon starts to "run".

    All power is available and ok. I cannot pinpoint to the exact place where to look for faulty components. Is someone able to help me out?

    Terence.
     
  2. GreenGiant

    GreenGiant

    842
    6
    Feb 9, 2012
    I know it sounds trivial but what signal are you giving it?
    are you using the reference pin to try and trigger it?
     
  3. Terence123

    Terence123

    11
    0
    Sep 17, 2012
    nope, a 1 khz sinus from a function generator 4v pp and ch1 on 1V. these were the requirements in the service manual
     
  4. ModemHead

    ModemHead

    69
    20
    Dec 2, 2010
    Start with trigger mode AUTO, trigger source INT from Ch 1, and hold-off control set to NORM. With the FG signal going into channel 1, you should be able to get a stable trace easily with the level control at about mid-rotation. If not, something is probably wrong inside the scope.

    The fact that you get a vertical line on the left side in NORM trigger mode suggests that something is wrong, because when triggered, there should be a trace, and when not triggered, the screen should be totally blanked. That's how NORM trigger mode is supposed to work.

    Does the trigger indicator ever light up during your testing? Often this indicator will blink occasionally when you move the trigger level control back and forth.

    Ground the vertical inputs. Switch to trigger mode NORM. Switch trigger source to LINE and set the trigger level to mid-rotation. The trigger indicator should light up and the scope should also produce a flat trace.

    You can also use a tee connector and input your FG signal into the external trigger input, then try EXT trigger source, to see if that does anything interesting.

    If you can get something to trigger the sweep, then the fault may be in trigger input selection circuitry, even as simple as dirty switch contacts. But if nothing ever triggers the sweep, the fault may lie deeper in the trigger section.

    Sounds like you already have the service manual, that's good. If you open the scope to start trouble-shooting, first thing to check is the power supplies for nominal DC level and AC ripple. Bad electrolytic caps cause all manner of troubles. Then proceed to the sweep generator/trigger section. Be mindful of high voltages, of course.

    For nitty-gritty trouble-shooting help, the TekScopes Yahoo group is a good resource.
     
  5. Terence123

    Terence123

    11
    0
    Sep 17, 2012
    Thx for the reply!

     
  6. ModemHead

    ModemHead

    69
    20
    Dec 2, 2010
    The 30V ripple sounds a little bit high but I doubt it would cause the triggering fault.

    Some general advice while you're waiting for better help from the TekScopes people: If the trigger indicator never comes on, I would start looking backwards from the circuitry that drives that indicator. If you've got a sample of the input signal coming in, but no trigger signals coming out, then you're probably in the right place. The Tek schematic should have DC voltage levels for various points, check those and look for serious differences. Keep in mind those voltages may depend on front-panel settings.

    Good luck!
     
  7. Terence123

    Terence123

    11
    0
    Sep 17, 2012
    thx! will do
     
  8. Andrzejj

    Andrzejj

    5
    0
    Nov 18, 2013
    I have exactly the same problem, can you tell me how you fixed it?
    I've measured all of the voltages, and somewhere its +/-0.1V, and somewhere its perfectly like it should, i think its all ok, i've also tested U421(5 transistrs in DIP16) and its working totally fine.
     
    Last edited: Nov 18, 2013
  9. Terence123

    Terence123

    11
    0
    Sep 17, 2012
    Hi,

    since i was busy waiting for repair parts, i got contract work abroad, and still are there now. With the scope still waiting... but, i traced the problem back to the double differential amplifier which needs replacement, I forgot the number but it was something like ca 3062... (so nr might be incorrect). Another problem was, that i order that parts from hongkong and found out they are smc-components. I probably did not check the package type...

    If you find the normal package type, pls let me know... :)

    T.
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    As long as there isn't a problem with the lower power dissipation, you can get adapter boards, solder the surface mount chip onto them, then solder the whole thing in place of the original.

    The adapter is a little larger than a DIL chip, so you need a few mm on either side to fit the adapter in. This is not often a problem.
     
  11. Andrzejj

    Andrzejj

    5
    0
    Nov 18, 2013
    Thanks for reply, i thought u wont reply, because its really old topic, as soon as i will be home i will check it. As far as i remember all of the packages are DIP-8 or DIP-16.
    @edit
    Isnt it CA3102 (U460 on tek schematic) ? Here you got the part of the schematic with it, it should remind it to you.
    [​IMG]
    btw. Its DIP16/DIL16 (dont really know the difference between it) and you can easily buy one on the ebay( its like 10 $ with shipping)
     
    Last edited: Nov 19, 2013
  12. Andrzejj

    Andrzejj

    5
    0
    Nov 18, 2013
    Ok, i borrowed another scope, there is 350mv p-p signal at the pin 6 of U460, and on the pin 13 there is only 50mv p-p, shouldn't it be same?
    There is signal on the 7th pin of the U480, but there is no signal out( pin 3), its like black magic for me, can you please tell me what to check? i totally dont understand this part of the scope...(just like logic gates :D)
    I can send you service manual via email, so you dont have to search for it(its PDF and its like 50mb, i cant convert it into image and also i cant do screenshot cause of the resolution.
    @edit i gave u wrong IC number... not U421 but U460 :D
     
    Last edited: Nov 23, 2013
  13. Andrzejj

    Andrzejj

    5
    0
    Nov 18, 2013
    up, i mistyped ICs numbers..
     
  14. Andrzejj

    Andrzejj

    5
    0
    Nov 18, 2013
    My tek is working perfectly now, i replaced mc10102( i bought it for 1 euro in PL but its quite rare, I've found it in only one shop)
     
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