502/Repairs: Difference between revisions
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(Created page with "__TOC__ ==Supply out of regulation== :'''Symptom:''' +350 V supply out of regulation (~300 V) :'''Root cause:''' C751 10 nF "Bumble Bee" leaky :'...") |
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==Disintegrated fan mounts== | |||
: See [[Fan mounts]]. | |||
==Supply out of regulation== | ==Supply out of regulation== | ||
:'''Symptom:''' +350 V supply out of regulation (~300 V) | :'''Symptom:''' +350 V supply out of regulation (~300 V) | ||
| Line 5: | Line 8: | ||
:'''Solution:''' Replace C751 | :'''Solution:''' Replace C751 | ||
==HV very low== | |||
:'''Symptom:''' HV very low, oscillator tube V800 gets very hot | |||
:'''Root cause:''' [[Bumble Bee capacitors|Black Beauty capacitors]] in HV circuit leaky | |||
:'''Solution:''' Replace all 6.8 nF HV caps | |||
==No sweep at slower speeds== | |||
:'''Symptom:''' In 1 ms/Div and slower, no sweep − trace stationary on left | |||
:'''Root cause:''' [[Bumble Bee capacitors]] in holdoff circuit leaky | |||
:'''Solution:''' Replace C180B-D | |||
==Burned-out HV transformer== | |||
:'''Symptom:''' HV transformer showing burns | |||
:'''Root cause:''' overload by earlier V800 failure caused by leaky HV caps | |||
:'''Solution:''' Replaced by 120-114 transformer (502) with 120-150 (from 502A) using only one cathode secondary. Note the grid winding has more turns on the 120-150, so a dropper resistor needs to be added to prevent the grid going too negative (no beam). | |||
[[Category:Instrument repair reports]] | [[Category:Instrument repair reports]] | ||
Latest revision as of 10:58, 6 July 2022
Disintegrated fan mounts
- See Fan mounts.
Supply out of regulation
- Symptom: +350 V supply out of regulation (~300 V)
- Root cause: C751 10 nF "Bumble Bee" leaky
- Solution: Replace C751
HV very low
- Symptom: HV very low, oscillator tube V800 gets very hot
- Root cause: Black Beauty capacitors in HV circuit leaky
- Solution: Replace all 6.8 nF HV caps
No sweep at slower speeds
- Symptom: In 1 ms/Div and slower, no sweep − trace stationary on left
- Root cause: Bumble Bee capacitors in holdoff circuit leaky
- Solution: Replace C180B-D
Burned-out HV transformer
- Symptom: HV transformer showing burns
- Root cause: overload by earlier V800 failure caused by leaky HV caps
- Solution: Replaced by 120-114 transformer (502) with 120-150 (from 502A) using only one cathode secondary. Note the grid winding has more turns on the 120-150, so a dropper resistor needs to be added to prevent the grid going too negative (no beam).