502/Repairs: Difference between revisions

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).

@@ Line 1: / Line 1: @@
 __TOC__
+==Disintegrated fan mounts==
+: See [[Fan mounts]].
 ==Supply out of regulation==
 :'''Symptom:''' +350 V supply out of regulation (~300 V)
@@ Line 15: / Line 18: @@
 :'''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]]