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Data...
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from new the IC7000 ran 14-18C hotter than ambient (20C).? The hot spots
aligned with thermal pads.
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Testing with a ditter on CW at half power netted a 30C climb in the hottest
areas.? The heatsink for the finals was at 54C, operation? at that level or
higher will impact the life of the finals and drivers (close thermal location).
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Opening the unit while hot showed NO FAN operation.? Heating the
thermister used to sense temps was no fan operation until it was over
45C at the sensor.? ??
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That is too hot for good lifespan.? That's based on my experience and
knowledge of reliability engineering.? ?Sure one unit may last for ever
but do that to 1000s of them and that will not be true.
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First fix tried was new thermister, then altered the circuit values for lower?
activation temp (~32C).? That helped when under stress (during high use
TX) but the unit was always very warm.? Relocating the thermister to the
finals (heatsink) helped keep them somewhat cooler.? Adding the fan mod
(resistor) caused a significant drop in?the case temp of +14-18C (over ambient)
measured earlier to +2- to +3C over ambient.? ? It also lowered the temps
of the finals and drivers?during intermittent operation.? ?Being cooler also
lowered the timebase (frequency) error and that showed most on
144 and 432 operations.
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Over all the high temps and thermal cycles is known to increase failure
rates over time.? Having the radio running generally cooler cannot hurt.
If dust is an issue then a occasional cleaning is worth doing.
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--
Allison
