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Analog meters deceased. Substitute strategy, sorta.
- Thread starter nomadradio
- Start date
ka3cjx@netscape.net Hope to get right side meter for SB-220. Plate voltage KV, Grid MA, Rel PWR. Please,
The one we have for the right-hand meter reads only grid current. The circuit board we add on the rear of the substitute meter adapts it to read grid current. Just hooking it directly in place of the old meter wouldn't work. The coil of the substitute meter requires more current than the factory original meter. The relative power and HV circuits don't deliver enough current to the meter coil. Our replacement meter just isn't compatible for those two features.
Grid current (or plate current) only.
Besides, the three fat dropping resistors in the HV meter circuit have a bad habit of failing on their own. Thought about providing exotic high-voltage resistors to replace the three 4.7 megohm 2 Watt carbon-comp parts in the HV circuit. But they would have to throw about five times the heat that the three factory resistors. That was what put this feature on the "never mind" list.
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Grid current (or plate current) only.
Besides, the three fat dropping resistors in the HV meter circuit have a bad habit of failing on their own. Thought about providing exotic high-voltage resistors to replace the three 4.7 megohm 2 Watt carbon-comp parts in the HV circuit. But they would have to throw about five times the heat that the three factory resistors. That was what put this feature on the "never mind" list.
73