585/Repairs: Difference between revisions
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:<gallery> | :<gallery> | ||
Electrolytic repair 1.jpg | Remove defective cap | Electrolytic repair 1.jpg | Remove defective cap | ||
Electrolytic repair 2.jpg | Cut can near base, remove guts | Electrolytic repair 2.jpg | Cut can near base (using a small hacksaw or a pipe cutter), remove guts | ||
Electrolytic repair 3.jpg | Fit modern cap | Electrolytic repair 3.jpg | Fit modern cap | ||
Electrolytic repair 4.jpg | Epoxy cap onto base | Electrolytic repair 4.jpg | Epoxy cap onto base | ||
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:--[[User:Peter|Peter]] ([[User talk:Peter|talk]]) 02:45, 4 May 2019 (PDT) | :--[[User:Peter|Peter]] ([[User talk:Peter|talk]]) 02:45, 4 May 2019 (PDT) | ||
== | ==Wavy trace == | ||
:'''Symptom:''' | :'''Symptom:''' Wavy trace | ||
:'''Root cause:''' C786 ( | :'''Root cause:''' C786 (100 µF 25 V) has high internal resistance (ESR ~ 20 Ω) causing +12.6 V regulator circuit to oscillate | ||
:'''Solution:''' | :'''Solution:''' Replace C786 with new part. | ||
:<gallery> | :<gallery> | ||
585 wavy trace.JPG | wavy trace | 585 wavy trace.JPG | wavy trace | ||
585_wavy_trace_new_electrolytics.JPG | | 585_wavy_trace_new_electrolytics.JPG | +12.6 v PSU with new eletrolytics. | ||
</gallery> | </gallery> | ||
:--[[User:Matt|Matt]] ([[User talk:Matt|Matt]]) 08:53, 5 May 2019 (PDT) | :--[[User:Matt|Matt]] ([[User talk:Matt|Matt]]) 08:53, 5 May 2019 (PDT) |
Latest revision as of 03:43, 29 March 2020
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 (using a small hacksaw or a pipe cutter), 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
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 (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.