>
>Hi Bill et al
>
>>>2) After I've been running the limit in an SSB QSO what's the recommended
>>>cool down period before I shut the power off?
>>
>>(Rich) My guess is c. ten-seconds cooldown for unprocessed SSB and
30-seconds
>>for RTTY. .
>
>I would suggest more like 3 - 4 minutes, Bill.
? The tube weighs about 198g.
>The 3-500z is a radiation-cooled
>tube i.e. most of the heat is infra-red radiated by the plate structure,
>and absorbed by the surrounding metalwork, circuitry, glass envelope, etc -
>the blower/fan should keep the tube glass seals at the right temperature,
>but usually does a POOR job of cooling the surroundings.
? would you like to make a wild and crazy guess as to a commercial
amplifier that has a perforated black panel next to the 3-500Z/8008
anodes?.
>You'll find that it takes anything up to 2 minutes for the orange/red colour
>of a hot 3-500z plate to die away.
>I've rewired all blowers/fans here so that they remain 'on' even after the
>filaments are switched 'off', then switch everything off once I'm sure it
>has properly cooled down.
? ... you use a thermocouple?
>
>>>That would allow me to not cycle the filaments just for the sake of
>>>getting the noise level down. I could even set up this blower control
circuit
>>>to run the blower the cool down period after I turn the power switch off
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