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585/Repairs

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Revision as of 04:17, 9 May 2019 by Matt (talk | contribs) (Wavy trace)
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Supplies out of regulation

Symptom: Several supplies out of regulation
Root cause: dry HV electrolytics
Solution: Rebuild caps using modern replacements
  • Remove defective cap

  • Cut can near base, remove guts

  • Fit modern cap

  • Epoxy cap onto base

  • --Peter (talk) 02:45, 4 May 2019 (PDT)

    HV low and trace invisible

    Symptom: No trace, HV low despite maximum setting
    Root cause: HV PIO "Bumble Bee" capacitors leaky (~180 μA at 2 kV); no trace because CRT grid too negative wrt. cathode
    Solution: Replace caps with modern ceramic equivalents
  • old PIO caps in place

  • old PIO caps removed

  • new ceramic caps

  • --Peter (talk) 02:45, 4 May 2019 (PDT)

    No trace

    Symptom: Trace invisible
    Root cause: Wiper of focus pot not in contact
    Solution: Disassemble focus pot, clean and re-seat wiper
    --Peter (talk) 02:45, 4 May 2019 (PDT)

    Trace disappearing

    Symptom: Trace fading after ~10 minutes operation
    Root cause: HV resonant cap (C808) leaky, overheating (visible bulge)
    Solution: Replace cap with modern ceramic equivalent
  • Thermal image

  • bulging cap

  • --Peter (talk) 02:45, 4 May 2019 (PDT)

    Time base inoperative

    Symptom: No trace
    Root cause: Lead of neon bulb in Miller integrator (B171?) broken
    Solution: Solder replacement lead after grinding away some glass (or replace neon)
  • broken lead

  • repaired leads (before cleaning and epoxy encapsulation)

  • --Peter (talk) 02:45, 4 May 2019 (PDT)

    Wavy trace

    Symptom: Wavy trace
    Root cause: C786 (100 µF 25 V) has high internal resistance (ESR ~ 20 Ω) causing +12.6 V regulator circuit to oscillate
    Solution: Replace C786 with new part.
  • wavy trace

  • +12.6 v PSU with new eletrolytics.

  • --Matt (Matt) 08:53, 5 May 2019 (PDT)