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GB7PZT > HF 04.05.03 21:01l 77 Lines 1963 Bytes #999 (0) @ WW
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From: gb7pzt@ve2pkt.#qbc.qc.can.noam
To: hf@ww
re: cooling
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From: I0ZV@IK0MIL.ILAZ.ITA.EU
To : HF@WW
Dear F6DQM,
in my opinion the situation can be different if you mean to cool GLASS
tubes (i.e. 3-500Z or EL519) or ceramic (similar to 4CX250).
For ceramic tubes the correct cooling require a certain amount of air that
depend only on the difference of pressure from below and top of the tube.
If the air is extracted, hot air will pass in the fan or blower and this
can be a problem. Usually the blower is placed to have a pressure below
the tube, and the pressure can be measured. Quite often - in amateurs
amplifiers - this pressure is below the value listed in the data sheet of
the tubes.
For the BIG glass tubes the cooling is necessary either for the sockets as
well for the caps, and any solution can be OK if the velocity of air is
adequate.
73 and Dx de I0ZV
Dear Gab, I must add that is usually advisable to have the blower going
ON for 2 to 5 minutes (depending on the size of the tube) AFTER the
amplifier is switched OFF. 73
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