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Problem with Tek 7844

Discussion in 'Troubleshooting and Repair' started by RaulV, Nov 24, 2011.

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  1. RaulV

    RaulV

    3
    0
    Nov 24, 2011
    Hi I am new here

    I have a tektronix 7844 scope. The problem is that not powers up, and a little periodic noise like a spark come from the power supply.

    I saw a post from another user (amolas) about same or similar problem. But I cant contact him (user not exists).

    Please if some knows what components must check, or something.

    Thanks
     
  2. davenn

    davenn Moderator

    13,799
    1,939
    Sep 5, 2009
    hi there,
    welcome to the forums :)

    do you have a service manual for it ? its going to be almost essential
    many are available on the www, do a google search if necessary

    I'm a member of a yahoo group for tektronix scopes ... it is a valuable resource of information for doing repairs.. join up and ask some questions :)

    Dave
     
  3. RaulV

    RaulV

    3
    0
    Nov 24, 2011
    Hi, thanks for answer.

    I have the scope 7844 instruction manual, with 436 pages, footprint boards, schematics and components. I alrready retire the power supply from scope, and separe the assemblies.
    I have multimeter, a general pasive component toolbox (Resistors, capacitors, some IC's, switches, etc), but not another scope to probe.

    What you say ? need I more stuff ?

    I will search the group in yahoo.
     
  4. davenn

    davenn Moderator

    13,799
    1,939
    Sep 5, 2009
    most tektronix scope service manuals have flow charts for fault finding
    eg. check point X for 5V if not correct, check this and this and this component etc
    I have found those faultfind charts very helpful in the past when working on my own Tek scope

    Have you been able to determine where in the PSU the clicking type noise is coming from ? the low voltage or a hi voltage section ?
    BE CAREFUL of the HV sections most of them have in excess of 2000V
    Have you used the manual to check the specified voltages at their correct locations ?

    do a few basic tests according to the manual and report back
    I dont have the service manual for that particular scope and am not familiar with the model

    Dave
     
  5. RaulV

    RaulV

    3
    0
    Nov 24, 2011
    Hi, I will reassembly the power supply, conect to scope and try to measure all the
    points where must have a know dc level.

    The noise came from HV section, and the problem is that I cannot measure there, besides this section cannot reach with the ps assembled.

    Anyway I dont lossing anything.

    Probably I will buy another scope, but the earlies model of tektronix are very expensive.

    By the way, I still waiting the aprove be a member of the tektronix group-

    Thanks.
     
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