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Post by Marc on Apr 6, 2010 10:14:12 GMT -5
Well got that socket V401 swapped out. Now how important is the heat shield on that tube??
Marc
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Post by 2600 on Apr 14, 2010 1:55:02 GMT -5
It's not a heat shield.
It's a faraday cage. It prevents the plate of the tube from radiating RF to the circuits around it. That tube is at the end of the RF chain in the receiver and has the highest RF level on it anywhere in the receiver section. It will "transmit" over a distance of an inch or two back into the input circuit.
If the receiver oscillates on AM with the shield removed, you can solder a wire to the old shield and lap-solder the other end to an exposed grounded lead on the top side of the pc board. This will usually do the job in a pinch. If it's gonna happen, it will usually be worst with the antenna disconnected, the RF Gain turned down, or when the noise level on the antenna is very low.
And if leaving it off causes no problems, that's easier. It's also possible that a replacement tube could cause oscillation trouble later that the tube you're using now doesn't cause. Tubes are not all created equal.
We always put it back. One less potential headache to worry about.
73
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Post by Marc on Apr 14, 2010 10:15:12 GMT -5
So far no prob with it off. the new socket was to large to put it back on but I will keep looking for one that will fit.
Marc
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