585/Repairs

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

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

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)

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)

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)

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)

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)