585/Repairs: Difference between revisions
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==wavy trace == | ==wavy trace == | ||
:'''Symptom:''' wavy trace | :'''Symptom:''' wavy trace | ||
:'''Root cause:''' | :'''Root cause:''' C786 (100µF 25V) has high internal resistor (ESR ~ 20 ohms). -12.6 v regulator ciruit is oscillating | ||
:'''Solution:''' Replacing of electrolytic capacitor | :'''Solution:''' Replacing of electrolytic capacitor C786 with new part. | ||
:<gallery> | :<gallery> |
Revision as of 08:58, 6 May 2019
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
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
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
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)
wavy trace
- Symptom: wavy trace
- Root cause: C786 (100µF 25V) has high internal resistor (ESR ~ 20 ohms). -12.6 v regulator ciruit is oscillating
- Solution: Replacing of electrolytic capacitor C786 with new part.
wavy trace
-12.6 v PSU with new eletrolytics.