Temperature controlled Fan.

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W4NNG
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Temperature controlled Fan.

Postby W4NNG » Sun Jan 03, 2021 3:06 pm

My 7000dle MKII is one of the units that came from the factory with fan is hardwired ON at maximum speed. Likely done to mitigate a heat problem when running 100wts ICAS. Suspect unit has the circuitry to have for the fan be temperature controlled.

Due power amp drive limits, will limit the Anan to a maximum of ~20 watts out. Is it possible to reconnect fan to the temp control circuit?

If not, on the units that have temp control, at what power out does the fan kick-on ?

Thanks for any feedback

Bob W4NNG
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w-u-2-o
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Re: Temperature controlled Fan.

Postby w-u-2-o » Sun Jan 03, 2021 3:54 pm

The original embodiment of the original 7000 fan controller, which is located on the PA/filter board, can be found here: viewtopic.php?f=17&t=2682&p=4660

I can only guess, but it would appear that the factory went away from that approach in order to eliminate the complaints about noisy and "rattling" fans associated with using a FET instead of a BJT, as also discussed in the above referenced link.

Not owning a newer 7000 with the always-on fan, I'm not at all sure how the newer ones are built. You would have to open yours up and see if the original controller circuitry is still on the board and how the fan is wired.

As for the fan controller turn-on temperature, you will have to look at the markings on U2 as populated on your board and the TC652 data sheet.

If you do decide to open up your unit, please let us know how the fan is wired and whether the fan controller components are still populated on the board.
w9mdb
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Re: Temperature controlled Fan.

Postby w9mdb » Sun Jan 03, 2021 4:10 pm

What's the fan do in the new boards? Mine is still on backorder.
Mike W9MDB
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Re: Temperature controlled Fan.

Postby W4NNG » Mon Jan 04, 2021 1:04 am

Thanks Scott

Having just read IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix, my inclination is to not go this route.

Am wondering if at low enough transmit power, the 7000,
1 - might not need a fan or
2 - A less CFM effective but much quieter fan could be used.

An 'ah-shucks' observation that appears to argue against this goal
1- At 20wtsRF out, it appears the rig is dissipating 97wts (PS draw on minus RF out)
2 - At 100wt RF rig dissipates 114wts

If I'm not missing something it appears dropping output power to 20wts, doesn't have too much impact on rig heat dissipation requirements

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