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549: Difference between revisions
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Repair issues - expanded C335 function.
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m (Repair issues - expanded C335 function.) |
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==Repair issues== | ==Repair issues== | ||
===C335=== | ===C335=== | ||
549 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. | 549 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> | <gallery> | ||
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549-areovox.png | Bad capacitor in horizontal amplifier schematic | 549-areovox.png | Bad capacitor in horizontal amplifier schematic | ||
549_badareovox.png | Location of bad capacitor in horizontal amplifier | 549_badareovox.png | Location of bad capacitor in horizontal amplifier | ||
Tek_549_C335.png | Location of bad capacitor in horizontal amplifier | |||
</gallery> | </gallery> | ||