549: Difference between revisions

549 (view source)

Revision as of 21:26, 17 April 2019

653 bytes added , 17 April 2019

m

Repair issues - expanded C335 function.

Rajesh

1,537

edits

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 ==Repair issues==
 ===C335===
-scopes from the Portland factory contain one black Areovox 0.5 µF / 400 V capacitor in the horizontal amplifier (in the middle of the upper chassis) which is often deteriorated. When this is the case, the trace is compressed on the right side.  It can be replaced with a modern 0.47 µF / 630 V (or higher) capacitor.  This problem does not appear to occur in Dutch-made 549s.
+scopes from the Portland factory contain one black Areovox 0.5 µF / 400 V capacitor in the horizontal amplifier (in the middle of the upper chassis) which is often deteriorated. When this is the case, the trace is compressed on the right side.  It can be replaced with a modern 0.47 µF / 630 V (or higher) capacitor.
+This capacitor is part of the beam steering arrangement during power-up to avoid screen burn. -150V power on pulse is coupled via this capacitor to the R/C340 network in  V343A's grid to move the beam to the left and off the screen during initial power up. Beam returns to screen after R/C340 discharges.
+This cap C335 can go leaky and affect the linearity of the trace. To confirm you could temporary disconnect this capacitor and power on the scope with intensity control at CCW, and after initial warm up of a minute increase the intensity to test if the problem disappears.
+This problem does not appear to occur in Dutch-made 549s.
 <gallery>
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 -areovox.png | Bad capacitor in horizontal amplifier schematic
 _badareovox.png  | Location of bad capacitor in horizontal amplifier
+Tek_549_C335.png | Location of bad capacitor in horizontal amplifier
 </gallery>