Scope Telequipment D61A;horizontal position fault

Discussion in 'General Electronics Chat' started by patpin, Mar 8, 2015.

  1. patpin

    Thread Starter Member

    Sep 15, 2012
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    Hallo,
    My X axis stops at the third vertical division (from the left) . I can only move the axis to the left I would like to have an X-axis image on the full screen. I have tried to adjust R113 which is supposed to be dooing that, but it does nothing.
    Horizontal is OK.
    I still can view (a small portion of) the calibarting signal (0,5V).
    Any ideas?
     
  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    You speak (well... write) as if the readers have intimate knowledge of the instrument in question (am I missing something?) --- A schematic of the 'deflection' circuitry would seem 'prerequisitory' of assistance...

    Best regards -- and with apologies for 'lexical liberties' :eek:
    HP
     
  3. patpin

    Thread Starter Member

    Sep 15, 2012
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    18
    Indeed, yr right. I add the diagram...
     
  4. Lundwall_Paul

    Member

    Oct 18, 2011
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    Sorry I am not comfortable opening zip files from unknown sources.
     
  5. patpin

    Thread Starter Member

    Sep 15, 2012
    226
    18
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    Outside of college - my only experience with Telequipment scopes is, that one of the plug-ins has a row of blade contacts on the side as well as the bulk connector at the back - these blade contacts can catch as the plug-in is being refitted and causes some odd faults.

    If all else fails - check for that.
     
  7. patpin

    Thread Starter Member

    Sep 15, 2012
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    contains only 2 jpg files which I could not include separately using "update a file"; this function simply doesn't find them ... dont worry. I m using Norton.
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    I say one of the two HOR OUTPUT driver transistors TR33 or TR37 is bad.

    [​IMG]
     
    Last edited: Mar 8, 2015
  9. patpin

    Thread Starter Member

    Sep 15, 2012
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    Thanks for yr answer. Can you tell me how to measure without a scope
     
  10. patpin

    Thread Starter Member

    Sep 15, 2012
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    It arrived after measuring a signal which appeared to be to high in Voltage for the scope (probably > 300V; with probe x10)
     
  11. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Responses to to these questions would be helpful...

    Does the sweep appear linear on the visible portion of the trace?
    Does R113 produce some effect on the trace over its (R113's) entire range? If not please explain...

    A cursory test of BJTs may be accomplished via use of a digital multimeter set to 'junction test' mode (such that the test EMF is sufficient to bias semiconductor junctions) --- Silicon devices should enter forward bias (B-E and B-C) in the range of 0.5v through 0.75v there should be no measurable conduction under reverse bias. Germanium devices will exhibit similar behavior but at significantly lower forward EMFs --- For best results this test should be preformed out-of-circuit

    Note: the procedure outlined above does not assay 'gain' (i.e. the characteristic quantified as one of '[hybrid] forward transadmittance [aka hFE]' or 'beta' -- dependent upon the system used by the 'characterizing agency') That said, it is generally sufficient when applied to investigation of conspicuous malfunction.

    Good luck :)

    Best Regards
    HP
     
    Last edited: Mar 9, 2015
  12. patpin

    Thread Starter Member

    Sep 15, 2012
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    18
    Yes the X axe appears lineair. I can judge better if I pull the time/div knob ; then the X axe is X5 and fills more than half of the screen. The R113 does nothing.
    TR33: BE 0,69; BC 0,67; TR35:BE 0,69; BC 0,68; all reverses give -;
     
  13. alfacliff

    Well-Known Member

    Dec 13, 2013
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    how about the y axis, is it working normal? if not, a common problem is the power supplies, one or more get dried out electrolytics and drop voltage. these days, I check all supply voltages on scopes (there are usually severeal different voltages out) by the way for those out there not familiar with telequipment, it is tektronix- uk.
     
  14. patpin

    Thread Starter Member

    Sep 15, 2012
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    X axis is functioning normaly. Could it be the sweep generator instead? (lenght of sweep?)
     
  15. MrChips

    Moderator

    Oct 2, 2009
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    Look for crud around the legs of TR31 and TR37.
     
  16. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Very well -- the junction analysis results, along with verified maintenance of linear response, effectively 'exonerate' TR33 & TR35 --- Moreover we now understand the difficulty to be that of balance -- as opposed to gain/distortion...

    Let's start with the 'too obvious' beginning with R113 itself and including all components affecting balance but exerting little or no effect upon gain...
    As a matter of course please verify the +110v and -13v supply EMFs

    Keep us posted :)
    HP

    EDIT: On a safety note, please be advised that the deflection plates will be near accelerator potential while, in some designs, the chassis will be near that of the cathode... (while this particular hazard does not appear manifest in this instrument one cannot be over cautious...)
     
    Last edited: Mar 9, 2015
  17. patpin

    Thread Starter Member

    Sep 15, 2012
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    No crud TR31 / 37..
     
  18. patpin

    Thread Starter Member

    Sep 15, 2012
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    I add 1 page of the manual treating tuning of X axe related items. telequipm-tuning hor.jpg telequipm-tuning hor.jpg telequipm-tuning hor.jpg
     
  19. patpin

    Thread Starter Member

    Sep 15, 2012
    226
    18
    Will post as soon as possible... have to enter hospital tomorr...
     
  20. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    So... a few thoughts...

    Please check R69 over its entire range with special attention to its ground and -13v connections, verify R66 and, again, the -13v supply EMF. --- It's 'telling' that S23 produces the proper effect...

    Best regards
    HP
     
    Last edited: Mar 9, 2015
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