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oscilloscope blurry with poor vertical lines

Discussion in 'Troubleshooting and Repair' started by josh1e, Jun 11, 2010.

  1. josh1e

    josh1e

    2
    0
    Jun 11, 2010
    Hi,

    I noticed some helpful posts on here through google searches, I hoped you might be able to help me

    I have been given an oscilloscope, I'm new to them and understand the (very) basic operation. The scope seemed fine when it was given to me, although after a cold winter in the brick shed on the back of the house, i've gone to use it & the scope is quite blurry, on the calibration sine wave, there is a distinct lack of / poor vertical line, I also noticed that the top horizontal line is sloped slightly, while the bottom line is straight... I cannot seem to get what i believe is a "crisp" image on it.. for the photo's the intensity is as low as possible, any higher just creates a halo effect around the original dot, focus is just below half way..

    I read that others have replaced transistors / resistors to improve this on tektronic scopes, however i was never given the front cover plate, so other than a goldstar Precision Co Ltd logo on the back and OS-9020P mainboard 1994 3.12 Goldstar Precision Ltd on the pcb, I have no knowledge of this model number (maybe someone recognises it?)

    I have searched google's image library, however so far i have only found tektronic versions.

    it is dual channel but quite a low frequency version, it has a philips tube (made in holland) with "fluke industrial BV" on the philips sticker.

    I have attached some photo's, if anyone can give me the model number that'd be a great start, if anyone knows how to repair the vertical lines & blur, that'd be even better.

    I've good soldering skills, access to a hot air station if required, although have never worked on tubes or HV tube pcb's, always steered away from them....

    I don't have another scope to use, but a good fluke dmm & npn / pnp transistor tester if they're needed....

    any help would be great- thanks
    josh1e
     

    Attached Files:

    Last edited: Jun 11, 2010
  2. shrtrnd

    shrtrnd

    3,670
    453
    Jan 15, 2010
    If you fix it, don't leave it to freeze again this winter. Condensation can form bringing cold item into the warm house. Assume you let it dry out for several days, before firing it up. My guess would be damage to one of the large electrolytic capacitors to your power supply. They don't like cold weather. Depending on your generator, it's not necessarily a bad thing to have weak vertical lines, depends on rise time of your signal source. How are your input cables to the scope? Most have a small trimmer cap adjustment, see if that helps. You may be able to adjust it. Make sure you're sure of you input signal first though, be sure of your generator source, and that the
    input cables themselves don't have a problem.
     
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